Initial commit. Basic models mostly done.

venv/lib/python3.8/site-packages/django/db/backends/base/base.py

@@ -0,0 +1,670 @@
+import copy
+import threading
+import time
+import warnings
+from collections import deque
+from contextlib import contextmanager
+
+import _thread
+import pytz
+
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.db import DEFAULT_DB_ALIAS
+from django.db.backends import utils
+from django.db.backends.base.validation import BaseDatabaseValidation
+from django.db.backends.signals import connection_created
+from django.db.transaction import TransactionManagementError
+from django.db.utils import DatabaseError, DatabaseErrorWrapper
+from django.utils import timezone
+from django.utils.asyncio import async_unsafe
+from django.utils.functional import cached_property
+
+NO_DB_ALIAS = '__no_db__'
+
+
+class BaseDatabaseWrapper:
+    """Represent a database connection."""
+    # Mapping of Field objects to their column types.
+    data_types = {}
+    # Mapping of Field objects to their SQL suffix such as AUTOINCREMENT.
+    data_types_suffix = {}
+    # Mapping of Field objects to their SQL for CHECK constraints.
+    data_type_check_constraints = {}
+    ops = None
+    vendor = 'unknown'
+    display_name = 'unknown'
+    SchemaEditorClass = None
+    # Classes instantiated in __init__().
+    client_class = None
+    creation_class = None
+    features_class = None
+    introspection_class = None
+    ops_class = None
+    validation_class = BaseDatabaseValidation
+
+    queries_limit = 9000
+
+    def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS):
+        # Connection related attributes.
+        # The underlying database connection.
+        self.connection = None
+        # `settings_dict` should be a dictionary containing keys such as
+        # NAME, USER, etc. It's called `settings_dict` instead of `settings`
+        # to disambiguate it from Django settings modules.
+        self.settings_dict = settings_dict
+        self.alias = alias
+        # Query logging in debug mode or when explicitly enabled.
+        self.queries_log = deque(maxlen=self.queries_limit)
+        self.force_debug_cursor = False
+
+        # Transaction related attributes.
+        # Tracks if the connection is in autocommit mode. Per PEP 249, by
+        # default, it isn't.
+        self.autocommit = False
+        # Tracks if the connection is in a transaction managed by 'atomic'.
+        self.in_atomic_block = False
+        # Increment to generate unique savepoint ids.
+        self.savepoint_state = 0
+        # List of savepoints created by 'atomic'.
+        self.savepoint_ids = []
+        # Tracks if the outermost 'atomic' block should commit on exit,
+        # ie. if autocommit was active on entry.
+        self.commit_on_exit = True
+        # Tracks if the transaction should be rolled back to the next
+        # available savepoint because of an exception in an inner block.
+        self.needs_rollback = False
+
+        # Connection termination related attributes.
+        self.close_at = None
+        self.closed_in_transaction = False
+        self.errors_occurred = False
+
+        # Thread-safety related attributes.
+        self._thread_sharing_lock = threading.Lock()
+        self._thread_sharing_count = 0
+        self._thread_ident = _thread.get_ident()
+
+        # A list of no-argument functions to run when the transaction commits.
+        # Each entry is an (sids, func) tuple, where sids is a set of the
+        # active savepoint IDs when this function was registered.
+        self.run_on_commit = []
+
+        # Should we run the on-commit hooks the next time set_autocommit(True)
+        # is called?
+        self.run_commit_hooks_on_set_autocommit_on = False
+
+        # A stack of wrappers to be invoked around execute()/executemany()
+        # calls. Each entry is a function taking five arguments: execute, sql,
+        # params, many, and context. It's the function's responsibility to
+        # call execute(sql, params, many, context).
+        self.execute_wrappers = []
+
+        self.client = self.client_class(self)
+        self.creation = self.creation_class(self)
+        self.features = self.features_class(self)
+        self.introspection = self.introspection_class(self)
+        self.ops = self.ops_class(self)
+        self.validation = self.validation_class(self)
+
+    def ensure_timezone(self):
+        """
+        Ensure the connection's timezone is set to `self.timezone_name` and
+        return whether it changed or not.
+        """
+        return False
+
+    @cached_property
+    def timezone(self):
+        """
+        Time zone for datetimes stored as naive values in the database.
+
+        Return a tzinfo object or None.
+
+        This is only needed when time zone support is enabled and the database
+        doesn't support time zones. (When the database supports time zones,
+        the adapter handles aware datetimes so Django doesn't need to.)
+        """
+        if not settings.USE_TZ:
+            return None
+        elif self.features.supports_timezones:
+            return None
+        elif self.settings_dict['TIME_ZONE'] is None:
+            return timezone.utc
+        else:
+            return pytz.timezone(self.settings_dict['TIME_ZONE'])
+
+    @cached_property
+    def timezone_name(self):
+        """
+        Name of the time zone of the database connection.
+        """
+        if not settings.USE_TZ:
+            return settings.TIME_ZONE
+        elif self.settings_dict['TIME_ZONE'] is None:
+            return 'UTC'
+        else:
+            return self.settings_dict['TIME_ZONE']
+
+    @property
+    def queries_logged(self):
+        return self.force_debug_cursor or settings.DEBUG
+
+    @property
+    def queries(self):
+        if len(self.queries_log) == self.queries_log.maxlen:
+            warnings.warn(
+                "Limit for query logging exceeded, only the last {} queries "
+                "will be returned.".format(self.queries_log.maxlen))
+        return list(self.queries_log)
+
+    # ##### Backend-specific methods for creating connections and cursors #####
+
+    def get_connection_params(self):
+        """Return a dict of parameters suitable for get_new_connection."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_connection_params() method')
+
+    def get_new_connection(self, conn_params):
+        """Open a connection to the database."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_new_connection() method')
+
+    def init_connection_state(self):
+        """Initialize the database connection settings."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require an init_connection_state() method')
+
+    def create_cursor(self, name=None):
+        """Create a cursor. Assume that a connection is established."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a create_cursor() method')
+
+    # ##### Backend-specific methods for creating connections #####
+
+    @async_unsafe
+    def connect(self):
+        """Connect to the database. Assume that the connection is closed."""
+        # Check for invalid configurations.
+        self.check_settings()
+        # In case the previous connection was closed while in an atomic block
+        self.in_atomic_block = False
+        self.savepoint_ids = []
+        self.needs_rollback = False
+        # Reset parameters defining when to close the connection
+        max_age = self.settings_dict['CONN_MAX_AGE']
+        self.close_at = None if max_age is None else time.monotonic() + max_age
+        self.closed_in_transaction = False
+        self.errors_occurred = False
+        # Establish the connection
+        conn_params = self.get_connection_params()
+        self.connection = self.get_new_connection(conn_params)
+        self.set_autocommit(self.settings_dict['AUTOCOMMIT'])
+        self.init_connection_state()
+        connection_created.send(sender=self.__class__, connection=self)
+
+        self.run_on_commit = []
+
+    def check_settings(self):
+        if self.settings_dict['TIME_ZONE'] is not None:
+            if not settings.USE_TZ:
+                raise ImproperlyConfigured(
+                    "Connection '%s' cannot set TIME_ZONE because USE_TZ is "
+                    "False." % self.alias)
+            elif self.features.supports_timezones:
+                raise ImproperlyConfigured(
+                    "Connection '%s' cannot set TIME_ZONE because its engine "
+                    "handles time zones conversions natively." % self.alias)
+
+    @async_unsafe
+    def ensure_connection(self):
+        """Guarantee that a connection to the database is established."""
+        if self.connection is None:
+            with self.wrap_database_errors:
+                self.connect()
+
+    # ##### Backend-specific wrappers for PEP-249 connection methods #####
+
+    def _prepare_cursor(self, cursor):
+        """
+        Validate the connection is usable and perform database cursor wrapping.
+        """
+        self.validate_thread_sharing()
+        if self.queries_logged:
+            wrapped_cursor = self.make_debug_cursor(cursor)
+        else:
+            wrapped_cursor = self.make_cursor(cursor)
+        return wrapped_cursor
+
+    def _cursor(self, name=None):
+        self.ensure_connection()
+        with self.wrap_database_errors:
+            return self._prepare_cursor(self.create_cursor(name))
+
+    def _commit(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.commit()
+
+    def _rollback(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.rollback()
+
+    def _close(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.close()
+
+    # ##### Generic wrappers for PEP-249 connection methods #####
+
+    @async_unsafe
+    def cursor(self):
+        """Create a cursor, opening a connection if necessary."""
+        return self._cursor()
+
+    @async_unsafe
+    def commit(self):
+        """Commit a transaction and reset the dirty flag."""
+        self.validate_thread_sharing()
+        self.validate_no_atomic_block()
+        self._commit()
+        # A successful commit means that the database connection works.
+        self.errors_occurred = False
+        self.run_commit_hooks_on_set_autocommit_on = True
+
+    @async_unsafe
+    def rollback(self):
+        """Roll back a transaction and reset the dirty flag."""
+        self.validate_thread_sharing()
+        self.validate_no_atomic_block()
+        self._rollback()
+        # A successful rollback means that the database connection works.
+        self.errors_occurred = False
+        self.needs_rollback = False
+        self.run_on_commit = []
+
+    @async_unsafe
+    def close(self):
+        """Close the connection to the database."""
+        self.validate_thread_sharing()
+        self.run_on_commit = []
+
+        # Don't call validate_no_atomic_block() to avoid making it difficult
+        # to get rid of a connection in an invalid state. The next connect()
+        # will reset the transaction state anyway.
+        if self.closed_in_transaction or self.connection is None:
+            return
+        try:
+            self._close()
+        finally:
+            if self.in_atomic_block:
+                self.closed_in_transaction = True
+                self.needs_rollback = True
+            else:
+                self.connection = None
+
+    # ##### Backend-specific savepoint management methods #####
+
+    def _savepoint(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_create_sql(sid))
+
+    def _savepoint_rollback(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_rollback_sql(sid))
+
+    def _savepoint_commit(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_commit_sql(sid))
+
+    def _savepoint_allowed(self):
+        # Savepoints cannot be created outside a transaction
+        return self.features.uses_savepoints and not self.get_autocommit()
+
+    # ##### Generic savepoint management methods #####
+
+    @async_unsafe
+    def savepoint(self):
+        """
+        Create a savepoint inside the current transaction. Return an
+        identifier for the savepoint that will be used for the subsequent
+        rollback or commit. Do nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        thread_ident = _thread.get_ident()
+        tid = str(thread_ident).replace('-', '')
+
+        self.savepoint_state += 1
+        sid = "s%s_x%d" % (tid, self.savepoint_state)
+
+        self.validate_thread_sharing()
+        self._savepoint(sid)
+
+        return sid
+
+    @async_unsafe
+    def savepoint_rollback(self, sid):
+        """
+        Roll back to a savepoint. Do nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        self.validate_thread_sharing()
+        self._savepoint_rollback(sid)
+
+        # Remove any callbacks registered while this savepoint was active.
+        self.run_on_commit = [
+            (sids, func) for (sids, func) in self.run_on_commit if sid not in sids
+        ]
+
+    @async_unsafe
+    def savepoint_commit(self, sid):
+        """
+        Release a savepoint. Do nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        self.validate_thread_sharing()
+        self._savepoint_commit(sid)
+
+    @async_unsafe
+    def clean_savepoints(self):
+        """
+        Reset the counter used to generate unique savepoint ids in this thread.
+        """
+        self.savepoint_state = 0
+
+    # ##### Backend-specific transaction management methods #####
+
+    def _set_autocommit(self, autocommit):
+        """
+        Backend-specific implementation to enable or disable autocommit.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a _set_autocommit() method')
+
+    # ##### Generic transaction management methods #####
+
+    def get_autocommit(self):
+        """Get the autocommit state."""
+        self.ensure_connection()
+        return self.autocommit
+
+    def set_autocommit(self, autocommit, force_begin_transaction_with_broken_autocommit=False):
+        """
+        Enable or disable autocommit.
+
+        The usual way to start a transaction is to turn autocommit off.
+        SQLite does not properly start a transaction when disabling
+        autocommit. To avoid this buggy behavior and to actually enter a new
+        transaction, an explicit BEGIN is required. Using
+        force_begin_transaction_with_broken_autocommit=True will issue an
+        explicit BEGIN with SQLite. This option will be ignored for other
+        backends.
+        """
+        self.validate_no_atomic_block()
+        self.ensure_connection()
+
+        start_transaction_under_autocommit = (
+            force_begin_transaction_with_broken_autocommit and not autocommit and
+            hasattr(self, '_start_transaction_under_autocommit')
+        )
+
+        if start_transaction_under_autocommit:
+            self._start_transaction_under_autocommit()
+        else:
+            self._set_autocommit(autocommit)
+
+        self.autocommit = autocommit
+
+        if autocommit and self.run_commit_hooks_on_set_autocommit_on:
+            self.run_and_clear_commit_hooks()
+            self.run_commit_hooks_on_set_autocommit_on = False
+
+    def get_rollback(self):
+        """Get the "needs rollback" flag -- for *advanced use* only."""
+        if not self.in_atomic_block:
+            raise TransactionManagementError(
+                "The rollback flag doesn't work outside of an 'atomic' block.")
+        return self.needs_rollback
+
+    def set_rollback(self, rollback):
+        """
+        Set or unset the "needs rollback" flag -- for *advanced use* only.
+        """
+        if not self.in_atomic_block:
+            raise TransactionManagementError(
+                "The rollback flag doesn't work outside of an 'atomic' block.")
+        self.needs_rollback = rollback
+
+    def validate_no_atomic_block(self):
+        """Raise an error if an atomic block is active."""
+        if self.in_atomic_block:
+            raise TransactionManagementError(
+                "This is forbidden when an 'atomic' block is active.")
+
+    def validate_no_broken_transaction(self):
+        if self.needs_rollback:
+            raise TransactionManagementError(
+                "An error occurred in the current transaction. You can't "
+                "execute queries until the end of the 'atomic' block.")
+
+    # ##### Foreign key constraints checks handling #####
+
+    @contextmanager
+    def constraint_checks_disabled(self):
+        """
+        Disable foreign key constraint checking.
+        """
+        disabled = self.disable_constraint_checking()
+        try:
+            yield
+        finally:
+            if disabled:
+                self.enable_constraint_checking()
+
+    def disable_constraint_checking(self):
+        """
+        Backends can implement as needed to temporarily disable foreign key
+        constraint checking. Should return True if the constraints were
+        disabled and will need to be reenabled.
+        """
+        return False
+
+    def enable_constraint_checking(self):
+        """
+        Backends can implement as needed to re-enable foreign key constraint
+        checking.
+        """
+        pass
+
+    def check_constraints(self, table_names=None):
+        """
+        Backends can override this method if they can apply constraint
+        checking (e.g. via "SET CONSTRAINTS ALL IMMEDIATE"). Should raise an
+        IntegrityError if any invalid foreign key references are encountered.
+        """
+        pass
+
+    # ##### Connection termination handling #####
+
+    def is_usable(self):
+        """
+        Test if the database connection is usable.
+
+        This method may assume that self.connection is not None.
+
+        Actual implementations should take care not to raise exceptions
+        as that may prevent Django from recycling unusable connections.
+        """
+        raise NotImplementedError(
+            "subclasses of BaseDatabaseWrapper may require an is_usable() method")
+
+    def close_if_unusable_or_obsolete(self):
+        """
+        Close the current connection if unrecoverable errors have occurred
+        or if it outlived its maximum age.
+        """
+        if self.connection is not None:
+            # If the application didn't restore the original autocommit setting,
+            # don't take chances, drop the connection.
+            if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
+                self.close()
+                return
+
+            # If an exception other than DataError or IntegrityError occurred
+            # since the last commit / rollback, check if the connection works.
+            if self.errors_occurred:
+                if self.is_usable():
+                    self.errors_occurred = False
+                else:
+                    self.close()
+                    return
+
+            if self.close_at is not None and time.monotonic() >= self.close_at:
+                self.close()
+                return
+
+    # ##### Thread safety handling #####
+
+    @property
+    def allow_thread_sharing(self):
+        with self._thread_sharing_lock:
+            return self._thread_sharing_count > 0
+
+    def inc_thread_sharing(self):
+        with self._thread_sharing_lock:
+            self._thread_sharing_count += 1
+
+    def dec_thread_sharing(self):
+        with self._thread_sharing_lock:
+            if self._thread_sharing_count <= 0:
+                raise RuntimeError('Cannot decrement the thread sharing count below zero.')
+            self._thread_sharing_count -= 1
+
+    def validate_thread_sharing(self):
+        """
+        Validate that the connection isn't accessed by another thread than the
+        one which originally created it, unless the connection was explicitly
+        authorized to be shared between threads (via the `inc_thread_sharing()`
+        method). Raise an exception if the validation fails.
+        """
+        if not (self.allow_thread_sharing or self._thread_ident == _thread.get_ident()):
+            raise DatabaseError(
+                "DatabaseWrapper objects created in a "
+                "thread can only be used in that same thread. The object "
+                "with alias '%s' was created in thread id %s and this is "
+                "thread id %s."
+                % (self.alias, self._thread_ident, _thread.get_ident())
+            )
+
+    # ##### Miscellaneous #####
+
+    def prepare_database(self):
+        """
+        Hook to do any database check or preparation, generally called before
+        migrating a project or an app.
+        """
+        pass
+
+    @cached_property
+    def wrap_database_errors(self):
+        """
+        Context manager and decorator that re-throws backend-specific database
+        exceptions using Django's common wrappers.
+        """
+        return DatabaseErrorWrapper(self)
+
+    def chunked_cursor(self):
+        """
+        Return a cursor that tries to avoid caching in the database (if
+        supported by the database), otherwise return a regular cursor.
+        """
+        return self.cursor()
+
+    def make_debug_cursor(self, cursor):
+        """Create a cursor that logs all queries in self.queries_log."""
+        return utils.CursorDebugWrapper(cursor, self)
+
+    def make_cursor(self, cursor):
+        """Create a cursor without debug logging."""
+        return utils.CursorWrapper(cursor, self)
+
+    @contextmanager
+    def temporary_connection(self):
+        """
+        Context manager that ensures that a connection is established, and
+        if it opened one, closes it to avoid leaving a dangling connection.
+        This is useful for operations outside of the request-response cycle.
+
+        Provide a cursor: with self.temporary_connection() as cursor: ...
+        """
+        must_close = self.connection is None
+        try:
+            with self.cursor() as cursor:
+                yield cursor
+        finally:
+            if must_close:
+                self.close()
+
+    @property
+    def _nodb_connection(self):
+        """
+        Return an alternative connection to be used when there is no need to
+        access the main database, specifically for test db creation/deletion.
+        This also prevents the production database from being exposed to
+        potential child threads while (or after) the test database is destroyed.
+        Refs #10868, #17786, #16969.
+        """
+        return self.__class__({**self.settings_dict, 'NAME': None}, alias=NO_DB_ALIAS)
+
+    def schema_editor(self, *args, **kwargs):
+        """
+        Return a new instance of this backend's SchemaEditor.
+        """
+        if self.SchemaEditorClass is None:
+            raise NotImplementedError(
+                'The SchemaEditorClass attribute of this database wrapper is still None')
+        return self.SchemaEditorClass(self, *args, **kwargs)
+
+    def on_commit(self, func):
+        if self.in_atomic_block:
+            # Transaction in progress; save for execution on commit.
+            self.run_on_commit.append((set(self.savepoint_ids), func))
+        elif not self.get_autocommit():
+            raise TransactionManagementError('on_commit() cannot be used in manual transaction management')
+        else:
+            # No transaction in progress and in autocommit mode; execute
+            # immediately.
+            func()
+
+    def run_and_clear_commit_hooks(self):
+        self.validate_no_atomic_block()
+        current_run_on_commit = self.run_on_commit
+        self.run_on_commit = []
+        while current_run_on_commit:
+            sids, func = current_run_on_commit.pop(0)
+            func()
+
+    @contextmanager
+    def execute_wrapper(self, wrapper):
+        """
+        Return a context manager under which the wrapper is applied to suitable
+        database query executions.
+        """
+        self.execute_wrappers.append(wrapper)
+        try:
+            yield
+        finally:
+            self.execute_wrappers.pop()
+
+    def copy(self, alias=None):
+        """
+        Return a copy of this connection.
+
+        For tests that require two connections to the same database.
+        """
+        settings_dict = copy.deepcopy(self.settings_dict)
+        if alias is None:
+            alias = self.alias
+        return type(self)(settings_dict, alias)

venv/lib/python3.8/site-packages/django/db/backends/base/client.py

@@ -0,0 +1,12 @@
+class BaseDatabaseClient:
+    """Encapsulate backend-specific methods for opening a client shell."""
+    # This should be a string representing the name of the executable
+    # (e.g., "psql"). Subclasses must override this.
+    executable_name = None
+
+    def __init__(self, connection):
+        # connection is an instance of BaseDatabaseWrapper.
+        self.connection = connection
+
+    def runshell(self):
+        raise NotImplementedError('subclasses of BaseDatabaseClient must provide a runshell() method')

venv/lib/python3.8/site-packages/django/db/backends/base/creation.py

@@ -0,0 +1,296 @@
+import os
+import sys
+from io import StringIO
+
+from django.apps import apps
+from django.conf import settings
+from django.core import serializers
+from django.db import router
+
+# The prefix to put on the default database name when creating
+# the test database.
+TEST_DATABASE_PREFIX = 'test_'
+
+
+class BaseDatabaseCreation:
+    """
+    Encapsulate backend-specific differences pertaining to creation and
+    destruction of the test database.
+    """
+    def __init__(self, connection):
+        self.connection = connection
+
+    @property
+    def _nodb_connection(self):
+        """
+        Used to be defined here, now moved to DatabaseWrapper.
+        """
+        return self.connection._nodb_connection
+
+    def log(self, msg):
+        sys.stderr.write(msg + os.linesep)
+
+    def create_test_db(self, verbosity=1, autoclobber=False, serialize=True, keepdb=False):
+        """
+        Create a test database, prompting the user for confirmation if the
+        database already exists. Return the name of the test database created.
+        """
+        # Don't import django.core.management if it isn't needed.
+        from django.core.management import call_command
+
+        test_database_name = self._get_test_db_name()
+
+        if verbosity >= 1:
+            action = 'Creating'
+            if keepdb:
+                action = "Using existing"
+
+            self.log('%s test database for alias %s...' % (
+                action,
+                self._get_database_display_str(verbosity, test_database_name),
+            ))
+
+        # We could skip this call if keepdb is True, but we instead
+        # give it the keepdb param. This is to handle the case
+        # where the test DB doesn't exist, in which case we need to
+        # create it, then just not destroy it. If we instead skip
+        # this, we will get an exception.
+        self._create_test_db(verbosity, autoclobber, keepdb)
+
+        self.connection.close()
+        settings.DATABASES[self.connection.alias]["NAME"] = test_database_name
+        self.connection.settings_dict["NAME"] = test_database_name
+
+        # We report migrate messages at one level lower than that requested.
+        # This ensures we don't get flooded with messages during testing
+        # (unless you really ask to be flooded).
+        call_command(
+            'migrate',
+            verbosity=max(verbosity - 1, 0),
+            interactive=False,
+            database=self.connection.alias,
+            run_syncdb=True,
+        )
+
+        # We then serialize the current state of the database into a string
+        # and store it on the connection. This slightly horrific process is so people
+        # who are testing on databases without transactions or who are using
+        # a TransactionTestCase still get a clean database on every test run.
+        if serialize:
+            self.connection._test_serialized_contents = self.serialize_db_to_string()
+
+        call_command('createcachetable', database=self.connection.alias)
+
+        # Ensure a connection for the side effect of initializing the test database.
+        self.connection.ensure_connection()
+
+        return test_database_name
+
+    def set_as_test_mirror(self, primary_settings_dict):
+        """
+        Set this database up to be used in testing as a mirror of a primary
+        database whose settings are given.
+        """
+        self.connection.settings_dict['NAME'] = primary_settings_dict['NAME']
+
+    def serialize_db_to_string(self):
+        """
+        Serialize all data in the database into a JSON string.
+        Designed only for test runner usage; will not handle large
+        amounts of data.
+        """
+        # Build list of all apps to serialize
+        from django.db.migrations.loader import MigrationLoader
+        loader = MigrationLoader(self.connection)
+        app_list = []
+        for app_config in apps.get_app_configs():
+            if (
+                app_config.models_module is not None and
+                app_config.label in loader.migrated_apps and
+                app_config.name not in settings.TEST_NON_SERIALIZED_APPS
+            ):
+                app_list.append((app_config, None))
+
+        # Make a function to iteratively return every object
+        def get_objects():
+            for model in serializers.sort_dependencies(app_list):
+                if (model._meta.can_migrate(self.connection) and
+                        router.allow_migrate_model(self.connection.alias, model)):
+                    queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)
+                    yield from queryset.iterator()
+        # Serialize to a string
+        out = StringIO()
+        serializers.serialize("json", get_objects(), indent=None, stream=out)
+        return out.getvalue()
+
+    def deserialize_db_from_string(self, data):
+        """
+        Reload the database with data from a string generated by
+        the serialize_db_to_string() method.
+        """
+        data = StringIO(data)
+        for obj in serializers.deserialize("json", data, using=self.connection.alias):
+            obj.save()
+
+    def _get_database_display_str(self, verbosity, database_name):
+        """
+        Return display string for a database for use in various actions.
+        """
+        return "'%s'%s" % (
+            self.connection.alias,
+            (" ('%s')" % database_name) if verbosity >= 2 else '',
+        )
+
+    def _get_test_db_name(self):
+        """
+        Internal implementation - return the name of the test DB that will be
+        created. Only useful when called from create_test_db() and
+        _create_test_db() and when no external munging is done with the 'NAME'
+        settings.
+        """
+        if self.connection.settings_dict['TEST']['NAME']:
+            return self.connection.settings_dict['TEST']['NAME']
+        return TEST_DATABASE_PREFIX + self.connection.settings_dict['NAME']
+
+    def _execute_create_test_db(self, cursor, parameters, keepdb=False):
+        cursor.execute('CREATE DATABASE %(dbname)s %(suffix)s' % parameters)
+
+    def _create_test_db(self, verbosity, autoclobber, keepdb=False):
+        """
+        Internal implementation - create the test db tables.
+        """
+        test_database_name = self._get_test_db_name()
+        test_db_params = {
+            'dbname': self.connection.ops.quote_name(test_database_name),
+            'suffix': self.sql_table_creation_suffix(),
+        }
+        # Create the test database and connect to it.
+        with self._nodb_connection.cursor() as cursor:
+            try:
+                self._execute_create_test_db(cursor, test_db_params, keepdb)
+            except Exception as e:
+                # if we want to keep the db, then no need to do any of the below,
+                # just return and skip it all.
+                if keepdb:
+                    return test_database_name
+
+                self.log('Got an error creating the test database: %s' % e)
+                if not autoclobber:
+                    confirm = input(
+                        "Type 'yes' if you would like to try deleting the test "
+                        "database '%s', or 'no' to cancel: " % test_database_name)
+                if autoclobber or confirm == 'yes':
+                    try:
+                        if verbosity >= 1:
+                            self.log('Destroying old test database for alias %s...' % (
+                                self._get_database_display_str(verbosity, test_database_name),
+                            ))
+                        cursor.execute('DROP DATABASE %(dbname)s' % test_db_params)
+                        self._execute_create_test_db(cursor, test_db_params, keepdb)
+                    except Exception as e:
+                        self.log('Got an error recreating the test database: %s' % e)
+                        sys.exit(2)
+                else:
+                    self.log('Tests cancelled.')
+                    sys.exit(1)
+
+        return test_database_name
+
+    def clone_test_db(self, suffix, verbosity=1, autoclobber=False, keepdb=False):
+        """
+        Clone a test database.
+        """
+        source_database_name = self.connection.settings_dict['NAME']
+
+        if verbosity >= 1:
+            action = 'Cloning test database'
+            if keepdb:
+                action = 'Using existing clone'
+            self.log('%s for alias %s...' % (
+                action,
+                self._get_database_display_str(verbosity, source_database_name),
+            ))
+
+        # We could skip this call if keepdb is True, but we instead
+        # give it the keepdb param. See create_test_db for details.
+        self._clone_test_db(suffix, verbosity, keepdb)
+
+    def get_test_db_clone_settings(self, suffix):
+        """
+        Return a modified connection settings dict for the n-th clone of a DB.
+        """
+        # When this function is called, the test database has been created
+        # already and its name has been copied to settings_dict['NAME'] so
+        # we don't need to call _get_test_db_name.
+        orig_settings_dict = self.connection.settings_dict
+        return {**orig_settings_dict, 'NAME': '{}_{}'.format(orig_settings_dict['NAME'], suffix)}
+
+    def _clone_test_db(self, suffix, verbosity, keepdb=False):
+        """
+        Internal implementation - duplicate the test db tables.
+        """
+        raise NotImplementedError(
+            "The database backend doesn't support cloning databases. "
+            "Disable the option to run tests in parallel processes.")
+
+    def destroy_test_db(self, old_database_name=None, verbosity=1, keepdb=False, suffix=None):
+        """
+        Destroy a test database, prompting the user for confirmation if the
+        database already exists.
+        """
+        self.connection.close()
+        if suffix is None:
+            test_database_name = self.connection.settings_dict['NAME']
+        else:
+            test_database_name = self.get_test_db_clone_settings(suffix)['NAME']
+
+        if verbosity >= 1:
+            action = 'Destroying'
+            if keepdb:
+                action = 'Preserving'
+            self.log('%s test database for alias %s...' % (
+                action,
+                self._get_database_display_str(verbosity, test_database_name),
+            ))
+
+        # if we want to preserve the database
+        # skip the actual destroying piece.
+        if not keepdb:
+            self._destroy_test_db(test_database_name, verbosity)
+
+        # Restore the original database name
+        if old_database_name is not None:
+            settings.DATABASES[self.connection.alias]["NAME"] = old_database_name
+            self.connection.settings_dict["NAME"] = old_database_name
+
+    def _destroy_test_db(self, test_database_name, verbosity):
+        """
+        Internal implementation - remove the test db tables.
+        """
+        # Remove the test database to clean up after
+        # ourselves. Connect to the previous database (not the test database)
+        # to do so, because it's not allowed to delete a database while being
+        # connected to it.
+        with self.connection._nodb_connection.cursor() as cursor:
+            cursor.execute("DROP DATABASE %s"
+                           % self.connection.ops.quote_name(test_database_name))
+
+    def sql_table_creation_suffix(self):
+        """
+        SQL to append to the end of the test table creation statements.
+        """
+        return ''
+
+    def test_db_signature(self):
+        """
+        Return a tuple with elements of self.connection.settings_dict (a
+        DATABASES setting value) that uniquely identify a database
+        accordingly to the RDBMS particularities.
+        """
+        settings_dict = self.connection.settings_dict
+        return (
+            settings_dict['HOST'],
+            settings_dict['PORT'],
+            settings_dict['ENGINE'],
+            self._get_test_db_name(),
+        )

venv/lib/python3.8/site-packages/django/db/backends/base/features.py

@@ -0,0 +1,320 @@
+from django.db.utils import ProgrammingError
+from django.utils.functional import cached_property
+
+
+class BaseDatabaseFeatures:
+    gis_enabled = False
+    allows_group_by_pk = False
+    allows_group_by_selected_pks = False
+    empty_fetchmany_value = []
+    update_can_self_select = True
+
+    # Does the backend distinguish between '' and None?
+    interprets_empty_strings_as_nulls = False
+
+    # Does the backend allow inserting duplicate NULL rows in a nullable
+    # unique field? All core backends implement this correctly, but other
+    # databases such as SQL Server do not.
+    supports_nullable_unique_constraints = True
+
+    # Does the backend allow inserting duplicate rows when a unique_together
+    # constraint exists and some fields are nullable but not all of them?
+    supports_partially_nullable_unique_constraints = True
+
+    can_use_chunked_reads = True
+    can_return_columns_from_insert = False
+    can_return_multiple_columns_from_insert = False
+    can_return_rows_from_bulk_insert = False
+    has_bulk_insert = True
+    uses_savepoints = True
+    can_release_savepoints = False
+
+    # If True, don't use integer foreign keys referring to, e.g., positive
+    # integer primary keys.
+    related_fields_match_type = False
+    allow_sliced_subqueries_with_in = True
+    has_select_for_update = False
+    has_select_for_update_nowait = False
+    has_select_for_update_skip_locked = False
+    has_select_for_update_of = False
+    # Does the database's SELECT FOR UPDATE OF syntax require a column rather
+    # than a table?
+    select_for_update_of_column = False
+
+    # Does the default test database allow multiple connections?
+    # Usually an indication that the test database is in-memory
+    test_db_allows_multiple_connections = True
+
+    # Can an object be saved without an explicit primary key?
+    supports_unspecified_pk = False
+
+    # Can a fixture contain forward references? i.e., are
+    # FK constraints checked at the end of transaction, or
+    # at the end of each save operation?
+    supports_forward_references = True
+
+    # Does the backend truncate names properly when they are too long?
+    truncates_names = False
+
+    # Is there a REAL datatype in addition to floats/doubles?
+    has_real_datatype = False
+    supports_subqueries_in_group_by = True
+
+    # Is there a true datatype for uuid?
+    has_native_uuid_field = False
+
+    # Is there a true datatype for timedeltas?
+    has_native_duration_field = False
+
+    # Does the database driver supports same type temporal data subtraction
+    # by returning the type used to store duration field?
+    supports_temporal_subtraction = False
+
+    # Does the __regex lookup support backreferencing and grouping?
+    supports_regex_backreferencing = True
+
+    # Can date/datetime lookups be performed using a string?
+    supports_date_lookup_using_string = True
+
+    # Can datetimes with timezones be used?
+    supports_timezones = True
+
+    # Does the database have a copy of the zoneinfo database?
+    has_zoneinfo_database = True
+
+    # When performing a GROUP BY, is an ORDER BY NULL required
+    # to remove any ordering?
+    requires_explicit_null_ordering_when_grouping = False
+
+    # Does the backend order NULL values as largest or smallest?
+    nulls_order_largest = False
+
+    # The database's limit on the number of query parameters.
+    max_query_params = None
+
+    # Can an object have an autoincrement primary key of 0? MySQL says No.
+    allows_auto_pk_0 = True
+
+    # Do we need to NULL a ForeignKey out, or can the constraint check be
+    # deferred
+    can_defer_constraint_checks = False
+
+    # date_interval_sql can properly handle mixed Date/DateTime fields and timedeltas
+    supports_mixed_date_datetime_comparisons = True
+
+    # Does the backend support tablespaces? Default to False because it isn't
+    # in the SQL standard.
+    supports_tablespaces = False
+
+    # Does the backend reset sequences between tests?
+    supports_sequence_reset = True
+
+    # Can the backend introspect the default value of a column?
+    can_introspect_default = True
+
+    # Confirm support for introspected foreign keys
+    # Every database can do this reliably, except MySQL,
+    # which can't do it for MyISAM tables
+    can_introspect_foreign_keys = True
+
+    # Can the backend introspect an AutoField, instead of an IntegerField?
+    can_introspect_autofield = False
+
+    # Can the backend introspect a BigIntegerField, instead of an IntegerField?
+    can_introspect_big_integer_field = True
+
+    # Can the backend introspect an BinaryField, instead of an TextField?
+    can_introspect_binary_field = True
+
+    # Can the backend introspect an DecimalField, instead of an FloatField?
+    can_introspect_decimal_field = True
+
+    # Can the backend introspect a DurationField, instead of a BigIntegerField?
+    can_introspect_duration_field = True
+
+    # Can the backend introspect an IPAddressField, instead of an CharField?
+    can_introspect_ip_address_field = False
+
+    # Can the backend introspect a PositiveIntegerField, instead of an IntegerField?
+    can_introspect_positive_integer_field = False
+
+    # Can the backend introspect a SmallIntegerField, instead of an IntegerField?
+    can_introspect_small_integer_field = False
+
+    # Can the backend introspect a TimeField, instead of a DateTimeField?
+    can_introspect_time_field = True
+
+    # Some backends may not be able to differentiate BigAutoField or
+    # SmallAutoField from other fields such as AutoField.
+    introspected_big_auto_field_type = 'BigAutoField'
+    introspected_small_auto_field_type = 'SmallAutoField'
+
+    # Some backends may not be able to differentiate BooleanField from other
+    # fields such as IntegerField.
+    introspected_boolean_field_type = 'BooleanField'
+
+    # Can the backend introspect the column order (ASC/DESC) for indexes?
+    supports_index_column_ordering = True
+
+    # Does the backend support introspection of materialized views?
+    can_introspect_materialized_views = False
+
+    # Support for the DISTINCT ON clause
+    can_distinct_on_fields = False
+
+    # Does the backend prevent running SQL queries in broken transactions?
+    atomic_transactions = True
+
+    # Can we roll back DDL in a transaction?
+    can_rollback_ddl = False
+
+    # Does it support operations requiring references rename in a transaction?
+    supports_atomic_references_rename = True
+
+    # Can we issue more than one ALTER COLUMN clause in an ALTER TABLE?
+    supports_combined_alters = False
+
+    # Does it support foreign keys?
+    supports_foreign_keys = True
+
+    # Can it create foreign key constraints inline when adding columns?
+    can_create_inline_fk = True
+
+    # Does it support CHECK constraints?
+    supports_column_check_constraints = True
+    supports_table_check_constraints = True
+    # Does the backend support introspection of CHECK constraints?
+    can_introspect_check_constraints = True
+
+    # Does the backend support 'pyformat' style ("... %(name)s ...", {'name': value})
+    # parameter passing? Note this can be provided by the backend even if not
+    # supported by the Python driver
+    supports_paramstyle_pyformat = True
+
+    # Does the backend require literal defaults, rather than parameterized ones?
+    requires_literal_defaults = False
+
+    # Does the backend require a connection reset after each material schema change?
+    connection_persists_old_columns = False
+
+    # What kind of error does the backend throw when accessing closed cursor?
+    closed_cursor_error_class = ProgrammingError
+
+    # Does 'a' LIKE 'A' match?
+    has_case_insensitive_like = True
+
+    # Suffix for backends that don't support "SELECT xxx;" queries.
+    bare_select_suffix = ''
+
+    # If NULL is implied on columns without needing to be explicitly specified
+    implied_column_null = False
+
+    # Does the backend support "select for update" queries with limit (and offset)?
+    supports_select_for_update_with_limit = True
+
+    # Does the backend ignore null expressions in GREATEST and LEAST queries unless
+    # every expression is null?
+    greatest_least_ignores_nulls = False
+
+    # Can the backend clone databases for parallel test execution?
+    # Defaults to False to allow third-party backends to opt-in.
+    can_clone_databases = False
+
+    # Does the backend consider table names with different casing to
+    # be equal?
+    ignores_table_name_case = False
+
+    # Place FOR UPDATE right after FROM clause. Used on MSSQL.
+    for_update_after_from = False
+
+    # Combinatorial flags
+    supports_select_union = True
+    supports_select_intersection = True
+    supports_select_difference = True
+    supports_slicing_ordering_in_compound = False
+    supports_parentheses_in_compound = True
+
+    # Does the database support SQL 2003 FILTER (WHERE ...) in aggregate
+    # expressions?
+    supports_aggregate_filter_clause = False
+
+    # Does the backend support indexing a TextField?
+    supports_index_on_text_field = True
+
+    # Does the backend support window expressions (expression OVER (...))?
+    supports_over_clause = False
+    supports_frame_range_fixed_distance = False
+
+    # Does the backend support CAST with precision?
+    supports_cast_with_precision = True
+
+    # How many second decimals does the database return when casting a value to
+    # a type with time?
+    time_cast_precision = 6
+
+    # SQL to create a procedure for use by the Django test suite. The
+    # functionality of the procedure isn't important.
+    create_test_procedure_without_params_sql = None
+    create_test_procedure_with_int_param_sql = None
+
+    # Does the backend support keyword parameters for cursor.callproc()?
+    supports_callproc_kwargs = False
+
+    # Convert CharField results from bytes to str in database functions.
+    db_functions_convert_bytes_to_str = False
+
+    # What formats does the backend EXPLAIN syntax support?
+    supported_explain_formats = set()
+
+    # Does DatabaseOperations.explain_query_prefix() raise ValueError if
+    # unknown kwargs are passed to QuerySet.explain()?
+    validates_explain_options = True
+
+    # Does the backend support the default parameter in lead() and lag()?
+    supports_default_in_lead_lag = True
+
+    # Does the backend support ignoring constraint or uniqueness errors during
+    # INSERT?
+    supports_ignore_conflicts = True
+
+    # Does this backend require casting the results of CASE expressions used
+    # in UPDATE statements to ensure the expression has the correct type?
+    requires_casted_case_in_updates = False
+
+    # Does the backend support partial indexes (CREATE INDEX ... WHERE ...)?
+    supports_partial_indexes = True
+    supports_functions_in_partial_indexes = True
+
+    # Does the database allow more than one constraint or index on the same
+    # field(s)?
+    allows_multiple_constraints_on_same_fields = True
+
+    # Does the backend support boolean expressions in the SELECT clause?
+    supports_boolean_expr_in_select_clause = True
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    @cached_property
+    def supports_explaining_query_execution(self):
+        """Does this backend support explaining query execution?"""
+        return self.connection.ops.explain_prefix is not None
+
+    @cached_property
+    def supports_transactions(self):
+        """Confirm support for transactions."""
+        with self.connection.cursor() as cursor:
+            cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
+            self.connection.set_autocommit(False)
+            cursor.execute('INSERT INTO ROLLBACK_TEST (X) VALUES (8)')
+            self.connection.rollback()
+            self.connection.set_autocommit(True)
+            cursor.execute('SELECT COUNT(X) FROM ROLLBACK_TEST')
+            count, = cursor.fetchone()
+            cursor.execute('DROP TABLE ROLLBACK_TEST')
+        return count == 0
+
+    def allows_group_by_selected_pks_on_model(self, model):
+        if not self.allows_group_by_selected_pks:
+            return False
+        return model._meta.managed

venv/lib/python3.8/site-packages/django/db/backends/base/introspection.py

@@ -0,0 +1,169 @@
+from collections import namedtuple
+
+# Structure returned by DatabaseIntrospection.get_table_list()
+TableInfo = namedtuple('TableInfo', ['name', 'type'])
+
+# Structure returned by the DB-API cursor.description interface (PEP 249)
+FieldInfo = namedtuple('FieldInfo', 'name type_code display_size internal_size precision scale null_ok default')
+
+
+class BaseDatabaseIntrospection:
+    """Encapsulate backend-specific introspection utilities."""
+    data_types_reverse = {}
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    def get_field_type(self, data_type, description):
+        """
+        Hook for a database backend to use the cursor description to
+        match a Django field type to a database column.
+
+        For Oracle, the column data_type on its own is insufficient to
+        distinguish between a FloatField and IntegerField, for example.
+        """
+        return self.data_types_reverse[data_type]
+
+    def identifier_converter(self, name):
+        """
+        Apply a conversion to the identifier for the purposes of comparison.
+
+        The default identifier converter is for case sensitive comparison.
+        """
+        return name
+
+    def table_names(self, cursor=None, include_views=False):
+        """
+        Return a list of names of all tables that exist in the database.
+        Sort the returned table list by Python's default sorting. Do NOT use
+        the database's ORDER BY here to avoid subtle differences in sorting
+        order between databases.
+        """
+        def get_names(cursor):
+            return sorted(ti.name for ti in self.get_table_list(cursor)
+                          if include_views or ti.type == 't')
+        if cursor is None:
+            with self.connection.cursor() as cursor:
+                return get_names(cursor)
+        return get_names(cursor)
+
+    def get_table_list(self, cursor):
+        """
+        Return an unsorted list of TableInfo named tuples of all tables and
+        views that exist in the database.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_table_list() method')
+
+    def get_migratable_models(self):
+        from django.apps import apps
+        from django.db import router
+        return (
+            model
+            for app_config in apps.get_app_configs()
+            for model in router.get_migratable_models(app_config, self.connection.alias)
+            if model._meta.can_migrate(self.connection)
+        )
+
+    def django_table_names(self, only_existing=False, include_views=True):
+        """
+        Return a list of all table names that have associated Django models and
+        are in INSTALLED_APPS.
+
+        If only_existing is True, include only the tables in the database.
+        """
+        tables = set()
+        for model in self.get_migratable_models():
+            if not model._meta.managed:
+                continue
+            tables.add(model._meta.db_table)
+            tables.update(
+                f.m2m_db_table() for f in model._meta.local_many_to_many
+                if f.remote_field.through._meta.managed
+            )
+        tables = list(tables)
+        if only_existing:
+            existing_tables = set(self.table_names(include_views=include_views))
+            tables = [
+                t
+                for t in tables
+                if self.identifier_converter(t) in existing_tables
+            ]
+        return tables
+
+    def installed_models(self, tables):
+        """
+        Return a set of all models represented by the provided list of table
+        names.
+        """
+        tables = set(map(self.identifier_converter, tables))
+        return {
+            m for m in self.get_migratable_models()
+            if self.identifier_converter(m._meta.db_table) in tables
+        }
+
+    def sequence_list(self):
+        """
+        Return a list of information about all DB sequences for all models in
+        all apps.
+        """
+        sequence_list = []
+        with self.connection.cursor() as cursor:
+            for model in self.get_migratable_models():
+                if not model._meta.managed:
+                    continue
+                if model._meta.swapped:
+                    continue
+                sequence_list.extend(self.get_sequences(cursor, model._meta.db_table, model._meta.local_fields))
+                for f in model._meta.local_many_to_many:
+                    # If this is an m2m using an intermediate table,
+                    # we don't need to reset the sequence.
+                    if f.remote_field.through._meta.auto_created:
+                        sequence = self.get_sequences(cursor, f.m2m_db_table())
+                        sequence_list.extend(sequence or [{'table': f.m2m_db_table(), 'column': None}])
+        return sequence_list
+
+    def get_sequences(self, cursor, table_name, table_fields=()):
+        """
+        Return a list of introspected sequences for table_name. Each sequence
+        is a dict: {'table': <table_name>, 'column': <column_name>}. An optional
+        'name' key can be added if the backend supports named sequences.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_sequences() method')
+
+    def get_key_columns(self, cursor, table_name):
+        """
+        Backends can override this to return a list of:
+            (column_name, referenced_table_name, referenced_column_name)
+        for all key columns in given table.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_key_columns() method')
+
+    def get_primary_key_column(self, cursor, table_name):
+        """
+        Return the name of the primary key column for the given table.
+        """
+        for constraint in self.get_constraints(cursor, table_name).values():
+            if constraint['primary_key']:
+                return constraint['columns'][0]
+        return None
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieve any constraints or keys (unique, pk, fk, check, index)
+        across one or more columns.
+
+        Return a dict mapping constraint names to their attributes,
+        where attributes is a dict with keys:
+         * columns: List of columns this covers
+         * primary_key: True if primary key, False otherwise
+         * unique: True if this is a unique constraint, False otherwise
+         * foreign_key: (table, column) of target, or None
+         * check: True if check constraint, False otherwise
+         * index: True if index, False otherwise.
+         * orders: The order (ASC/DESC) defined for the columns of indexes
+         * type: The type of the index (btree, hash, etc.)
+
+        Some backends may return special constraint names that don't exist
+        if they don't name constraints of a certain type (e.g. SQLite)
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_constraints() method')

venv/lib/python3.8/site-packages/django/db/backends/base/operations.py

@@ -0,0 +1,681 @@
+import datetime
+import decimal
+from importlib import import_module
+
+import sqlparse
+
+from django.conf import settings
+from django.db import NotSupportedError, transaction
+from django.db.backends import utils
+from django.utils import timezone
+from django.utils.encoding import force_str
+
+
+class BaseDatabaseOperations:
+    """
+    Encapsulate backend-specific differences, such as the way a backend
+    performs ordering or calculates the ID of a recently-inserted row.
+    """
+    compiler_module = "django.db.models.sql.compiler"
+
+    # Integer field safe ranges by `internal_type` as documented
+    # in docs/ref/models/fields.txt.
+    integer_field_ranges = {
+        'SmallIntegerField': (-32768, 32767),
+        'IntegerField': (-2147483648, 2147483647),
+        'BigIntegerField': (-9223372036854775808, 9223372036854775807),
+        'PositiveSmallIntegerField': (0, 32767),
+        'PositiveIntegerField': (0, 2147483647),
+        'SmallAutoField': (-32768, 32767),
+        'AutoField': (-2147483648, 2147483647),
+        'BigAutoField': (-9223372036854775808, 9223372036854775807),
+    }
+    set_operators = {
+        'union': 'UNION',
+        'intersection': 'INTERSECT',
+        'difference': 'EXCEPT',
+    }
+    # Mapping of Field.get_internal_type() (typically the model field's class
+    # name) to the data type to use for the Cast() function, if different from
+    # DatabaseWrapper.data_types.
+    cast_data_types = {}
+    # CharField data type if the max_length argument isn't provided.
+    cast_char_field_without_max_length = None
+
+    # Start and end points for window expressions.
+    PRECEDING = 'PRECEDING'
+    FOLLOWING = 'FOLLOWING'
+    UNBOUNDED_PRECEDING = 'UNBOUNDED ' + PRECEDING
+    UNBOUNDED_FOLLOWING = 'UNBOUNDED ' + FOLLOWING
+    CURRENT_ROW = 'CURRENT ROW'
+
+    # Prefix for EXPLAIN queries, or None EXPLAIN isn't supported.
+    explain_prefix = None
+
+    def __init__(self, connection):
+        self.connection = connection
+        self._cache = None
+
+    def autoinc_sql(self, table, column):
+        """
+        Return any SQL needed to support auto-incrementing primary keys, or
+        None if no SQL is necessary.
+
+        This SQL is executed when a table is created.
+        """
+        return None
+
+    def bulk_batch_size(self, fields, objs):
+        """
+        Return the maximum allowed batch size for the backend. The fields
+        are the fields going to be inserted in the batch, the objs contains
+        all the objects to be inserted.
+        """
+        return len(objs)
+
+    def cache_key_culling_sql(self):
+        """
+        Return an SQL query that retrieves the first cache key greater than the
+        n smallest.
+
+        This is used by the 'db' cache backend to determine where to start
+        culling.
+        """
+        return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
+
+    def unification_cast_sql(self, output_field):
+        """
+        Given a field instance, return the SQL that casts the result of a union
+        to that type. The resulting string should contain a '%s' placeholder
+        for the expression being cast.
+        """
+        return '%s'
+
+    def date_extract_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'year', 'month', or 'day', return the SQL that
+        extracts a value from the given date field field_name.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_extract_sql() method')
+
+    def date_interval_sql(self, timedelta):
+        """
+        Implement the date interval functionality for expressions.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_interval_sql() method')
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'year', 'month', or 'day', return the SQL that
+        truncates the given date field field_name to a date object with only
+        the given specificity.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_trunc_sql() method.')
+
+    def datetime_cast_date_sql(self, field_name, tzname):
+        """
+        Return the SQL to cast a datetime value to date value.
+        """
+        raise NotImplementedError(
+            'subclasses of BaseDatabaseOperations may require a '
+            'datetime_cast_date_sql() method.'
+        )
+
+    def datetime_cast_time_sql(self, field_name, tzname):
+        """
+        Return the SQL to cast a datetime value to time value.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_cast_time_sql() method')
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        """
+        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute', or
+        'second', return the SQL that extracts a value from the given
+        datetime field field_name.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_extract_sql() method')
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        """
+        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute', or
+        'second', return the SQL that truncates the given datetime field
+        field_name to a datetime object with only the given specificity.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_trunc_sql() method')
+
+    def time_trunc_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'hour', 'minute' or 'second', return the SQL
+        that truncates the given time field field_name to a time object with
+        only the given specificity.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a time_trunc_sql() method')
+
+    def time_extract_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'hour', 'minute', or 'second', return the SQL
+        that extracts a value from the given time field field_name.
+        """
+        return self.date_extract_sql(lookup_type, field_name)
+
+    def deferrable_sql(self):
+        """
+        Return the SQL to make a constraint "initially deferred" during a
+        CREATE TABLE statement.
+        """
+        return ''
+
+    def distinct_sql(self, fields, params):
+        """
+        Return an SQL DISTINCT clause which removes duplicate rows from the
+        result set. If any fields are given, only check the given fields for
+        duplicates.
+        """
+        if fields:
+            raise NotSupportedError('DISTINCT ON fields is not supported by this database backend')
+        else:
+            return ['DISTINCT'], []
+
+    def fetch_returned_insert_columns(self, cursor):
+        """
+        Given a cursor object that has just performed an INSERT...RETURNING
+        statement into a table, return the newly created data.
+        """
+        return cursor.fetchone()
+
+    def field_cast_sql(self, db_type, internal_type):
+        """
+        Given a column type (e.g. 'BLOB', 'VARCHAR') and an internal type
+        (e.g. 'GenericIPAddressField'), return the SQL to cast it before using
+        it in a WHERE statement. The resulting string should contain a '%s'
+        placeholder for the column being searched against.
+        """
+        return '%s'
+
+    def force_no_ordering(self):
+        """
+        Return a list used in the "ORDER BY" clause to force no ordering at
+        all. Return an empty list to include nothing in the ordering.
+        """
+        return []
+
+    def for_update_sql(self, nowait=False, skip_locked=False, of=()):
+        """
+        Return the FOR UPDATE SQL clause to lock rows for an update operation.
+        """
+        return 'FOR UPDATE%s%s%s' % (
+            ' OF %s' % ', '.join(of) if of else '',
+            ' NOWAIT' if nowait else '',
+            ' SKIP LOCKED' if skip_locked else '',
+        )
+
+    def _get_limit_offset_params(self, low_mark, high_mark):
+        offset = low_mark or 0
+        if high_mark is not None:
+            return (high_mark - offset), offset
+        elif offset:
+            return self.connection.ops.no_limit_value(), offset
+        return None, offset
+
+    def limit_offset_sql(self, low_mark, high_mark):
+        """Return LIMIT/OFFSET SQL clause."""
+        limit, offset = self._get_limit_offset_params(low_mark, high_mark)
+        return ' '.join(sql for sql in (
+            ('LIMIT %d' % limit) if limit else None,
+            ('OFFSET %d' % offset) if offset else None,
+        ) if sql)
+
+    def last_executed_query(self, cursor, sql, params):
+        """
+        Return a string of the query last executed by the given cursor, with
+        placeholders replaced with actual values.
+
+        `sql` is the raw query containing placeholders and `params` is the
+        sequence of parameters. These are used by default, but this method
+        exists for database backends to provide a better implementation
+        according to their own quoting schemes.
+        """
+        # Convert params to contain string values.
+        def to_string(s):
+            return force_str(s, strings_only=True, errors='replace')
+        if isinstance(params, (list, tuple)):
+            u_params = tuple(to_string(val) for val in params)
+        elif params is None:
+            u_params = ()
+        else:
+            u_params = {to_string(k): to_string(v) for k, v in params.items()}
+
+        return "QUERY = %r - PARAMS = %r" % (sql, u_params)
+
+    def last_insert_id(self, cursor, table_name, pk_name):
+        """
+        Given a cursor object that has just performed an INSERT statement into
+        a table that has an auto-incrementing ID, return the newly created ID.
+
+        `pk_name` is the name of the primary-key column.
+        """
+        return cursor.lastrowid
+
+    def lookup_cast(self, lookup_type, internal_type=None):
+        """
+        Return the string to use in a query when performing lookups
+        ("contains", "like", etc.). It should contain a '%s' placeholder for
+        the column being searched against.
+        """
+        return "%s"
+
+    def max_in_list_size(self):
+        """
+        Return the maximum number of items that can be passed in a single 'IN'
+        list condition, or None if the backend does not impose a limit.
+        """
+        return None
+
+    def max_name_length(self):
+        """
+        Return the maximum length of table and column names, or None if there
+        is no limit.
+        """
+        return None
+
+    def no_limit_value(self):
+        """
+        Return the value to use for the LIMIT when we are wanting "LIMIT
+        infinity". Return None if the limit clause can be omitted in this case.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a no_limit_value() method')
+
+    def pk_default_value(self):
+        """
+        Return the value to use during an INSERT statement to specify that
+        the field should use its default value.
+        """
+        return 'DEFAULT'
+
+    def prepare_sql_script(self, sql):
+        """
+        Take an SQL script that may contain multiple lines and return a list
+        of statements to feed to successive cursor.execute() calls.
+
+        Since few databases are able to process raw SQL scripts in a single
+        cursor.execute() call and PEP 249 doesn't talk about this use case,
+        the default implementation is conservative.
+        """
+        return [
+            sqlparse.format(statement, strip_comments=True)
+            for statement in sqlparse.split(sql) if statement
+        ]
+
+    def process_clob(self, value):
+        """
+        Return the value of a CLOB column, for backends that return a locator
+        object that requires additional processing.
+        """
+        return value
+
+    def return_insert_columns(self, fields):
+        """
+        For backends that support returning columns as part of an insert query,
+        return the SQL and params to append to the INSERT query. The returned
+        fragment should contain a format string to hold the appropriate column.
+        """
+        pass
+
+    def compiler(self, compiler_name):
+        """
+        Return the SQLCompiler class corresponding to the given name,
+        in the namespace corresponding to the `compiler_module` attribute
+        on this backend.
+        """
+        if self._cache is None:
+            self._cache = import_module(self.compiler_module)
+        return getattr(self._cache, compiler_name)
+
+    def quote_name(self, name):
+        """
+        Return a quoted version of the given table, index, or column name. Do
+        not quote the given name if it's already been quoted.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a quote_name() method')
+
+    def random_function_sql(self):
+        """Return an SQL expression that returns a random value."""
+        return 'RANDOM()'
+
+    def regex_lookup(self, lookup_type):
+        """
+        Return the string to use in a query when performing regular expression
+        lookups (using "regex" or "iregex"). It should contain a '%s'
+        placeholder for the column being searched against.
+
+        If the feature is not supported (or part of it is not supported), raise
+        NotImplementedError.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a regex_lookup() method')
+
+    def savepoint_create_sql(self, sid):
+        """
+        Return the SQL for starting a new savepoint. Only required if the
+        "uses_savepoints" feature is True. The "sid" parameter is a string
+        for the savepoint id.
+        """
+        return "SAVEPOINT %s" % self.quote_name(sid)
+
+    def savepoint_commit_sql(self, sid):
+        """
+        Return the SQL for committing the given savepoint.
+        """
+        return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
+
+    def savepoint_rollback_sql(self, sid):
+        """
+        Return the SQL for rolling back the given savepoint.
+        """
+        return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
+
+    def set_time_zone_sql(self):
+        """
+        Return the SQL that will set the connection's time zone.
+
+        Return '' if the backend doesn't support time zones.
+        """
+        return ''
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        """
+        Return a list of SQL statements required to remove all data from
+        the given database tables (without actually removing the tables
+        themselves) and the SQL statements required to reset the sequences
+        passed in `sequences`.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+
+        The `allow_cascade` argument determines whether truncation may cascade
+        to tables with foreign keys pointing the tables being truncated.
+        PostgreSQL requires a cascade even if these tables are empty.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations must provide a sql_flush() method')
+
+    def execute_sql_flush(self, using, sql_list):
+        """Execute a list of SQL statements to flush the database."""
+        with transaction.atomic(using=using, savepoint=self.connection.features.can_rollback_ddl):
+            with self.connection.cursor() as cursor:
+                for sql in sql_list:
+                    cursor.execute(sql)
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        """
+        Return a list of the SQL statements required to reset sequences
+        passed in `sequences`.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+        """
+        return []
+
+    def sequence_reset_sql(self, style, model_list):
+        """
+        Return a list of the SQL statements required to reset sequences for
+        the given models.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+        """
+        return []  # No sequence reset required by default.
+
+    def start_transaction_sql(self):
+        """Return the SQL statement required to start a transaction."""
+        return "BEGIN;"
+
+    def end_transaction_sql(self, success=True):
+        """Return the SQL statement required to end a transaction."""
+        if not success:
+            return "ROLLBACK;"
+        return "COMMIT;"
+
+    def tablespace_sql(self, tablespace, inline=False):
+        """
+        Return the SQL that will be used in a query to define the tablespace.
+
+        Return '' if the backend doesn't support tablespaces.
+
+        If `inline` is True, append the SQL to a row; otherwise append it to
+        the entire CREATE TABLE or CREATE INDEX statement.
+        """
+        return ''
+
+    def prep_for_like_query(self, x):
+        """Prepare a value for use in a LIKE query."""
+        return str(x).replace("\\", "\\\\").replace("%", r"\%").replace("_", r"\_")
+
+    # Same as prep_for_like_query(), but called for "iexact" matches, which
+    # need not necessarily be implemented using "LIKE" in the backend.
+    prep_for_iexact_query = prep_for_like_query
+
+    def validate_autopk_value(self, value):
+        """
+        Certain backends do not accept some values for "serial" fields
+        (for example zero in MySQL). Raise a ValueError if the value is
+        invalid, otherwise return the validated value.
+        """
+        return value
+
+    def adapt_unknown_value(self, value):
+        """
+        Transform a value to something compatible with the backend driver.
+
+        This method only depends on the type of the value. It's designed for
+        cases where the target type isn't known, such as .raw() SQL queries.
+        As a consequence it may not work perfectly in all circumstances.
+        """
+        if isinstance(value, datetime.datetime):   # must be before date
+            return self.adapt_datetimefield_value(value)
+        elif isinstance(value, datetime.date):
+            return self.adapt_datefield_value(value)
+        elif isinstance(value, datetime.time):
+            return self.adapt_timefield_value(value)
+        elif isinstance(value, decimal.Decimal):
+            return self.adapt_decimalfield_value(value)
+        else:
+            return value
+
+    def adapt_datefield_value(self, value):
+        """
+        Transform a date value to an object compatible with what is expected
+        by the backend driver for date columns.
+        """
+        if value is None:
+            return None
+        return str(value)
+
+    def adapt_datetimefield_value(self, value):
+        """
+        Transform a datetime value to an object compatible with what is expected
+        by the backend driver for datetime columns.
+        """
+        if value is None:
+            return None
+        return str(value)
+
+    def adapt_timefield_value(self, value):
+        """
+        Transform a time value to an object compatible with what is expected
+        by the backend driver for time columns.
+        """
+        if value is None:
+            return None
+        if timezone.is_aware(value):
+            raise ValueError("Django does not support timezone-aware times.")
+        return str(value)
+
+    def adapt_decimalfield_value(self, value, max_digits=None, decimal_places=None):
+        """
+        Transform a decimal.Decimal value to an object compatible with what is
+        expected by the backend driver for decimal (numeric) columns.
+        """
+        return utils.format_number(value, max_digits, decimal_places)
+
+    def adapt_ipaddressfield_value(self, value):
+        """
+        Transform a string representation of an IP address into the expected
+        type for the backend driver.
+        """
+        return value or None
+
+    def year_lookup_bounds_for_date_field(self, value):
+        """
+        Return a two-elements list with the lower and upper bound to be used
+        with a BETWEEN operator to query a DateField value using a year
+        lookup.
+
+        `value` is an int, containing the looked-up year.
+        """
+        first = datetime.date(value, 1, 1)
+        second = datetime.date(value, 12, 31)
+        first = self.adapt_datefield_value(first)
+        second = self.adapt_datefield_value(second)
+        return [first, second]
+
+    def year_lookup_bounds_for_datetime_field(self, value):
+        """
+        Return a two-elements list with the lower and upper bound to be used
+        with a BETWEEN operator to query a DateTimeField value using a year
+        lookup.
+
+        `value` is an int, containing the looked-up year.
+        """
+        first = datetime.datetime(value, 1, 1)
+        second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
+        if settings.USE_TZ:
+            tz = timezone.get_current_timezone()
+            first = timezone.make_aware(first, tz)
+            second = timezone.make_aware(second, tz)
+        first = self.adapt_datetimefield_value(first)
+        second = self.adapt_datetimefield_value(second)
+        return [first, second]
+
+    def get_db_converters(self, expression):
+        """
+        Return a list of functions needed to convert field data.
+
+        Some field types on some backends do not provide data in the correct
+        format, this is the hook for converter functions.
+        """
+        return []
+
+    def convert_durationfield_value(self, value, expression, connection):
+        if value is not None:
+            return datetime.timedelta(0, 0, value)
+
+    def check_expression_support(self, expression):
+        """
+        Check that the backend supports the provided expression.
+
+        This is used on specific backends to rule out known expressions
+        that have problematic or nonexistent implementations. If the
+        expression has a known problem, the backend should raise
+        NotSupportedError.
+        """
+        pass
+
+    def conditional_expression_supported_in_where_clause(self, expression):
+        """
+        Return True, if the conditional expression is supported in the WHERE
+        clause.
+        """
+        return True
+
+    def combine_expression(self, connector, sub_expressions):
+        """
+        Combine a list of subexpressions into a single expression, using
+        the provided connecting operator. This is required because operators
+        can vary between backends (e.g., Oracle with %% and &) and between
+        subexpression types (e.g., date expressions).
+        """
+        conn = ' %s ' % connector
+        return conn.join(sub_expressions)
+
+    def combine_duration_expression(self, connector, sub_expressions):
+        return self.combine_expression(connector, sub_expressions)
+
+    def binary_placeholder_sql(self, value):
+        """
+        Some backends require special syntax to insert binary content (MySQL
+        for example uses '_binary %s').
+        """
+        return '%s'
+
+    def modify_insert_params(self, placeholder, params):
+        """
+        Allow modification of insert parameters. Needed for Oracle Spatial
+        backend due to #10888.
+        """
+        return params
+
+    def integer_field_range(self, internal_type):
+        """
+        Given an integer field internal type (e.g. 'PositiveIntegerField'),
+        return a tuple of the (min_value, max_value) form representing the
+        range of the column type bound to the field.
+        """
+        return self.integer_field_ranges[internal_type]
+
+    def subtract_temporals(self, internal_type, lhs, rhs):
+        if self.connection.features.supports_temporal_subtraction:
+            lhs_sql, lhs_params = lhs
+            rhs_sql, rhs_params = rhs
+            return '(%s - %s)' % (lhs_sql, rhs_sql), (*lhs_params, *rhs_params)
+        raise NotSupportedError("This backend does not support %s subtraction." % internal_type)
+
+    def window_frame_start(self, start):
+        if isinstance(start, int):
+            if start < 0:
+                return '%d %s' % (abs(start), self.PRECEDING)
+            elif start == 0:
+                return self.CURRENT_ROW
+        elif start is None:
+            return self.UNBOUNDED_PRECEDING
+        raise ValueError("start argument must be a negative integer, zero, or None, but got '%s'." % start)
+
+    def window_frame_end(self, end):
+        if isinstance(end, int):
+            if end == 0:
+                return self.CURRENT_ROW
+            elif end > 0:
+                return '%d %s' % (end, self.FOLLOWING)
+        elif end is None:
+            return self.UNBOUNDED_FOLLOWING
+        raise ValueError("end argument must be a positive integer, zero, or None, but got '%s'." % end)
+
+    def window_frame_rows_start_end(self, start=None, end=None):
+        """
+        Return SQL for start and end points in an OVER clause window frame.
+        """
+        if not self.connection.features.supports_over_clause:
+            raise NotSupportedError('This backend does not support window expressions.')
+        return self.window_frame_start(start), self.window_frame_end(end)
+
+    def window_frame_range_start_end(self, start=None, end=None):
+        return self.window_frame_rows_start_end(start, end)
+
+    def explain_query_prefix(self, format=None, **options):
+        if not self.connection.features.supports_explaining_query_execution:
+            raise NotSupportedError('This backend does not support explaining query execution.')
+        if format:
+            supported_formats = self.connection.features.supported_explain_formats
+            normalized_format = format.upper()
+            if normalized_format not in supported_formats:
+                msg = '%s is not a recognized format.' % normalized_format
+                if supported_formats:
+                    msg += ' Allowed formats: %s' % ', '.join(sorted(supported_formats))
+                raise ValueError(msg)
+        if options:
+            raise ValueError('Unknown options: %s' % ', '.join(sorted(options.keys())))
+        return self.explain_prefix
+
+    def insert_statement(self, ignore_conflicts=False):
+        return 'INSERT INTO'
+
+    def ignore_conflicts_suffix_sql(self, ignore_conflicts=None):
+        return ''

venv/lib/python3.8/site-packages/django/db/backends/base/validation.py

@@ -0,0 +1,25 @@
+class BaseDatabaseValidation:
+    """Encapsulate backend-specific validation."""
+    def __init__(self, connection):
+        self.connection = connection
+
+    def check(self, **kwargs):
+        return []
+
+    def check_field(self, field, **kwargs):
+        errors = []
+        # Backends may implement a check_field_type() method.
+        if (hasattr(self, 'check_field_type') and
+                # Ignore any related fields.
+                not getattr(field, 'remote_field', None)):
+            # Ignore fields with unsupported features.
+            db_supports_all_required_features = all(
+                getattr(self.connection.features, feature, False)
+                for feature in field.model._meta.required_db_features
+            )
+            if db_supports_all_required_features:
+                field_type = field.db_type(self.connection)
+                # Ignore non-concrete fields.
+                if field_type is not None:
+                    errors.extend(self.check_field_type(field, field_type))
+        return errors

venv/lib/python3.8/site-packages/django/db/backends/ddl_references.py

@@ -0,0 +1,194 @@
+"""
+Helpers to manipulate deferred DDL statements that might need to be adjusted or
+discarded within when executing a migration.
+"""
+
+
+class Reference:
+    """Base class that defines the reference interface."""
+
+    def references_table(self, table):
+        """
+        Return whether or not this instance references the specified table.
+        """
+        return False
+
+    def references_column(self, table, column):
+        """
+        Return whether or not this instance references the specified column.
+        """
+        return False
+
+    def rename_table_references(self, old_table, new_table):
+        """
+        Rename all references to the old_name to the new_table.
+        """
+        pass
+
+    def rename_column_references(self, table, old_column, new_column):
+        """
+        Rename all references to the old_column to the new_column.
+        """
+        pass
+
+    def __repr__(self):
+        return '<%s %r>' % (self.__class__.__name__, str(self))
+
+    def __str__(self):
+        raise NotImplementedError('Subclasses must define how they should be converted to string.')
+
+
+class Table(Reference):
+    """Hold a reference to a table."""
+
+    def __init__(self, table, quote_name):
+        self.table = table
+        self.quote_name = quote_name
+
+    def references_table(self, table):
+        return self.table == table
+
+    def rename_table_references(self, old_table, new_table):
+        if self.table == old_table:
+            self.table = new_table
+
+    def __str__(self):
+        return self.quote_name(self.table)
+
+
+class TableColumns(Table):
+    """Base class for references to multiple columns of a table."""
+
+    def __init__(self, table, columns):
+        self.table = table
+        self.columns = columns
+
+    def references_column(self, table, column):
+        return self.table == table and column in self.columns
+
+    def rename_column_references(self, table, old_column, new_column):
+        if self.table == table:
+            for index, column in enumerate(self.columns):
+                if column == old_column:
+                    self.columns[index] = new_column
+
+
+class Columns(TableColumns):
+    """Hold a reference to one or many columns."""
+
+    def __init__(self, table, columns, quote_name, col_suffixes=()):
+        self.quote_name = quote_name
+        self.col_suffixes = col_suffixes
+        super().__init__(table, columns)
+
+    def __str__(self):
+        def col_str(column, idx):
+            try:
+                return self.quote_name(column) + self.col_suffixes[idx]
+            except IndexError:
+                return self.quote_name(column)
+
+        return ', '.join(col_str(column, idx) for idx, column in enumerate(self.columns))
+
+
+class IndexName(TableColumns):
+    """Hold a reference to an index name."""
+
+    def __init__(self, table, columns, suffix, create_index_name):
+        self.suffix = suffix
+        self.create_index_name = create_index_name
+        super().__init__(table, columns)
+
+    def __str__(self):
+        return self.create_index_name(self.table, self.columns, self.suffix)
+
+
+class IndexColumns(Columns):
+    def __init__(self, table, columns, quote_name, col_suffixes=(), opclasses=()):
+        self.opclasses = opclasses
+        super().__init__(table, columns, quote_name, col_suffixes)
+
+    def __str__(self):
+        def col_str(column, idx):
+            # Index.__init__() guarantees that self.opclasses is the same
+            # length as self.columns.
+            col = '{} {}'.format(self.quote_name(column), self.opclasses[idx])
+            try:
+                col = '{} {}'.format(col, self.col_suffixes[idx])
+            except IndexError:
+                pass
+            return col
+
+        return ', '.join(col_str(column, idx) for idx, column in enumerate(self.columns))
+
+
+class ForeignKeyName(TableColumns):
+    """Hold a reference to a foreign key name."""
+
+    def __init__(self, from_table, from_columns, to_table, to_columns, suffix_template, create_fk_name):
+        self.to_reference = TableColumns(to_table, to_columns)
+        self.suffix_template = suffix_template
+        self.create_fk_name = create_fk_name
+        super().__init__(from_table, from_columns,)
+
+    def references_table(self, table):
+        return super().references_table(table) or self.to_reference.references_table(table)
+
+    def references_column(self, table, column):
+        return (
+            super().references_column(table, column) or
+            self.to_reference.references_column(table, column)
+        )
+
+    def rename_table_references(self, old_table, new_table):
+        super().rename_table_references(old_table, new_table)
+        self.to_reference.rename_table_references(old_table, new_table)
+
+    def rename_column_references(self, table, old_column, new_column):
+        super().rename_column_references(table, old_column, new_column)
+        self.to_reference.rename_column_references(table, old_column, new_column)
+
+    def __str__(self):
+        suffix = self.suffix_template % {
+            'to_table': self.to_reference.table,
+            'to_column': self.to_reference.columns[0],
+        }
+        return self.create_fk_name(self.table, self.columns, suffix)
+
+
+class Statement(Reference):
+    """
+    Statement template and formatting parameters container.
+
+    Allows keeping a reference to a statement without interpolating identifiers
+    that might have to be adjusted if they're referencing a table or column
+    that is removed
+    """
+    def __init__(self, template, **parts):
+        self.template = template
+        self.parts = parts
+
+    def references_table(self, table):
+        return any(
+            hasattr(part, 'references_table') and part.references_table(table)
+            for part in self.parts.values()
+        )
+
+    def references_column(self, table, column):
+        return any(
+            hasattr(part, 'references_column') and part.references_column(table, column)
+            for part in self.parts.values()
+        )
+
+    def rename_table_references(self, old_table, new_table):
+        for part in self.parts.values():
+            if hasattr(part, 'rename_table_references'):
+                part.rename_table_references(old_table, new_table)
+
+    def rename_column_references(self, table, old_column, new_column):
+        for part in self.parts.values():
+            if hasattr(part, 'rename_column_references'):
+                part.rename_column_references(table, old_column, new_column)
+
+    def __str__(self):
+        return self.template % self.parts

venv/lib/python3.8/site-packages/django/db/backends/dummy/base.py

@@ -0,0 +1,73 @@
+"""
+Dummy database backend for Django.
+
+Django uses this if the database ENGINE setting is empty (None or empty string).
+
+Each of these API functions, except connection.close(), raise
+ImproperlyConfigured.
+"""
+
+from django.core.exceptions import ImproperlyConfigured
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.client import BaseDatabaseClient
+from django.db.backends.base.creation import BaseDatabaseCreation
+from django.db.backends.base.introspection import BaseDatabaseIntrospection
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.backends.dummy.features import DummyDatabaseFeatures
+
+
+def complain(*args, **kwargs):
+    raise ImproperlyConfigured("settings.DATABASES is improperly configured. "
+                               "Please supply the ENGINE value. Check "
+                               "settings documentation for more details.")
+
+
+def ignore(*args, **kwargs):
+    pass
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    quote_name = complain
+
+
+class DatabaseClient(BaseDatabaseClient):
+    runshell = complain
+
+
+class DatabaseCreation(BaseDatabaseCreation):
+    create_test_db = ignore
+    destroy_test_db = ignore
+
+
+class DatabaseIntrospection(BaseDatabaseIntrospection):
+    get_table_list = complain
+    get_table_description = complain
+    get_relations = complain
+    get_indexes = complain
+    get_key_columns = complain
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    operators = {}
+    # Override the base class implementations with null
+    # implementations. Anything that tries to actually
+    # do something raises complain; anything that tries
+    # to rollback or undo something raises ignore.
+    _cursor = complain
+    ensure_connection = complain
+    _commit = complain
+    _rollback = ignore
+    _close = ignore
+    _savepoint = ignore
+    _savepoint_commit = complain
+    _savepoint_rollback = ignore
+    _set_autocommit = complain
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DummyDatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+
+    def is_usable(self):
+        return True

venv/lib/python3.8/site-packages/django/db/backends/dummy/features.py

@@ -0,0 +1,6 @@
+from django.db.backends.base.features import BaseDatabaseFeatures
+
+
+class DummyDatabaseFeatures(BaseDatabaseFeatures):
+    supports_transactions = False
+    uses_savepoints = False

venv/lib/python3.8/site-packages/django/db/backends/mysql/base.py

@@ -0,0 +1,363 @@
+"""
+MySQL database backend for Django.
+
+Requires mysqlclient: https://pypi.org/project/mysqlclient/
+"""
+import re
+
+from django.core.exceptions import ImproperlyConfigured
+from django.db import utils
+from django.db.backends import utils as backend_utils
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.utils.asyncio import async_unsafe
+from django.utils.functional import cached_property
+
+try:
+    import MySQLdb as Database
+except ImportError as err:
+    raise ImproperlyConfigured(
+        'Error loading MySQLdb module.\n'
+        'Did you install mysqlclient?'
+    ) from err
+
+from MySQLdb.constants import CLIENT, FIELD_TYPE                # isort:skip
+from MySQLdb.converters import conversions                      # isort:skip
+
+# Some of these import MySQLdb, so import them after checking if it's installed.
+from .client import DatabaseClient                          # isort:skip
+from .creation import DatabaseCreation                      # isort:skip
+from .features import DatabaseFeatures                      # isort:skip
+from .introspection import DatabaseIntrospection            # isort:skip
+from .operations import DatabaseOperations                  # isort:skip
+from .schema import DatabaseSchemaEditor                    # isort:skip
+from .validation import DatabaseValidation                  # isort:skip
+
+version = Database.version_info
+if version < (1, 3, 13):
+    raise ImproperlyConfigured('mysqlclient 1.3.13 or newer is required; you have %s.' % Database.__version__)
+
+
+# MySQLdb returns TIME columns as timedelta -- they are more like timedelta in
+# terms of actual behavior as they are signed and include days -- and Django
+# expects time.
+django_conversions = {
+    **conversions,
+    **{FIELD_TYPE.TIME: backend_utils.typecast_time},
+}
+
+# This should match the numerical portion of the version numbers (we can treat
+# versions like 5.0.24 and 5.0.24a as the same).
+server_version_re = re.compile(r'(\d{1,2})\.(\d{1,2})\.(\d{1,2})')
+
+
+class CursorWrapper:
+    """
+    A thin wrapper around MySQLdb's normal cursor class that catches particular
+    exception instances and reraises them with the correct types.
+
+    Implemented as a wrapper, rather than a subclass, so that it isn't stuck
+    to the particular underlying representation returned by Connection.cursor().
+    """
+    codes_for_integrityerror = (
+        1048,  # Column cannot be null
+        1690,  # BIGINT UNSIGNED value is out of range
+        3819,  # CHECK constraint is violated
+        4025,  # CHECK constraint failed
+    )
+
+    def __init__(self, cursor):
+        self.cursor = cursor
+
+    def execute(self, query, args=None):
+        try:
+            # args is None means no string interpolation
+            return self.cursor.execute(query, args)
+        except Database.OperationalError as e:
+            # Map some error codes to IntegrityError, since they seem to be
+            # misclassified and Django would prefer the more logical place.
+            if e.args[0] in self.codes_for_integrityerror:
+                raise utils.IntegrityError(*tuple(e.args))
+            raise
+
+    def executemany(self, query, args):
+        try:
+            return self.cursor.executemany(query, args)
+        except Database.OperationalError as e:
+            # Map some error codes to IntegrityError, since they seem to be
+            # misclassified and Django would prefer the more logical place.
+            if e.args[0] in self.codes_for_integrityerror:
+                raise utils.IntegrityError(*tuple(e.args))
+            raise
+
+    def __getattr__(self, attr):
+        return getattr(self.cursor, attr)
+
+    def __iter__(self):
+        return iter(self.cursor)
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    vendor = 'mysql'
+    # This dictionary maps Field objects to their associated MySQL column
+    # types, as strings. Column-type strings can contain format strings; they'll
+    # be interpolated against the values of Field.__dict__ before being output.
+    # If a column type is set to None, it won't be included in the output.
+    data_types = {
+        'AutoField': 'integer AUTO_INCREMENT',
+        'BigAutoField': 'bigint AUTO_INCREMENT',
+        'BinaryField': 'longblob',
+        'BooleanField': 'bool',
+        'CharField': 'varchar(%(max_length)s)',
+        'DateField': 'date',
+        'DateTimeField': 'datetime(6)',
+        'DecimalField': 'numeric(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'bigint',
+        'FileField': 'varchar(%(max_length)s)',
+        'FilePathField': 'varchar(%(max_length)s)',
+        'FloatField': 'double precision',
+        'IntegerField': 'integer',
+        'BigIntegerField': 'bigint',
+        'IPAddressField': 'char(15)',
+        'GenericIPAddressField': 'char(39)',
+        'NullBooleanField': 'bool',
+        'OneToOneField': 'integer',
+        'PositiveIntegerField': 'integer UNSIGNED',
+        'PositiveSmallIntegerField': 'smallint UNSIGNED',
+        'SlugField': 'varchar(%(max_length)s)',
+        'SmallAutoField': 'smallint AUTO_INCREMENT',
+        'SmallIntegerField': 'smallint',
+        'TextField': 'longtext',
+        'TimeField': 'time(6)',
+        'UUIDField': 'char(32)',
+    }
+
+    # For these data types:
+    # - MySQL < 8.0.13 and MariaDB < 10.2.1 don't accept default values and
+    #   implicitly treat them as nullable
+    # - all versions of MySQL and MariaDB don't support full width database
+    #   indexes
+    _limited_data_types = (
+        'tinyblob', 'blob', 'mediumblob', 'longblob', 'tinytext', 'text',
+        'mediumtext', 'longtext', 'json',
+    )
+
+    operators = {
+        'exact': '= %s',
+        'iexact': 'LIKE %s',
+        'contains': 'LIKE BINARY %s',
+        'icontains': 'LIKE %s',
+        'gt': '> %s',
+        'gte': '>= %s',
+        'lt': '< %s',
+        'lte': '<= %s',
+        'startswith': 'LIKE BINARY %s',
+        'endswith': 'LIKE BINARY %s',
+        'istartswith': 'LIKE %s',
+        'iendswith': 'LIKE %s',
+    }
+
+    # The patterns below are used to generate SQL pattern lookup clauses when
+    # the right-hand side of the lookup isn't a raw string (it might be an expression
+    # or the result of a bilateral transformation).
+    # In those cases, special characters for LIKE operators (e.g. \, *, _) should be
+    # escaped on database side.
+    #
+    # Note: we use str.format() here for readability as '%' is used as a wildcard for
+    # the LIKE operator.
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\\', '\\\\'), '%%', '\%%'), '_', '\_')"
+    pattern_ops = {
+        'contains': "LIKE BINARY CONCAT('%%', {}, '%%')",
+        'icontains': "LIKE CONCAT('%%', {}, '%%')",
+        'startswith': "LIKE BINARY CONCAT({}, '%%')",
+        'istartswith': "LIKE CONCAT({}, '%%')",
+        'endswith': "LIKE BINARY CONCAT('%%', {})",
+        'iendswith': "LIKE CONCAT('%%', {})",
+    }
+
+    isolation_levels = {
+        'read uncommitted',
+        'read committed',
+        'repeatable read',
+        'serializable',
+    }
+
+    Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+    validation_class = DatabaseValidation
+
+    def get_connection_params(self):
+        kwargs = {
+            'conv': django_conversions,
+            'charset': 'utf8',
+        }
+        settings_dict = self.settings_dict
+        if settings_dict['USER']:
+            kwargs['user'] = settings_dict['USER']
+        if settings_dict['NAME']:
+            kwargs['db'] = settings_dict['NAME']
+        if settings_dict['PASSWORD']:
+            kwargs['passwd'] = settings_dict['PASSWORD']
+        if settings_dict['HOST'].startswith('/'):
+            kwargs['unix_socket'] = settings_dict['HOST']
+        elif settings_dict['HOST']:
+            kwargs['host'] = settings_dict['HOST']
+        if settings_dict['PORT']:
+            kwargs['port'] = int(settings_dict['PORT'])
+        # We need the number of potentially affected rows after an
+        # "UPDATE", not the number of changed rows.
+        kwargs['client_flag'] = CLIENT.FOUND_ROWS
+        # Validate the transaction isolation level, if specified.
+        options = settings_dict['OPTIONS'].copy()
+        isolation_level = options.pop('isolation_level', 'read committed')
+        if isolation_level:
+            isolation_level = isolation_level.lower()
+            if isolation_level not in self.isolation_levels:
+                raise ImproperlyConfigured(
+                    "Invalid transaction isolation level '%s' specified.\n"
+                    "Use one of %s, or None." % (
+                        isolation_level,
+                        ', '.join("'%s'" % s for s in sorted(self.isolation_levels))
+                    ))
+        self.isolation_level = isolation_level
+        kwargs.update(options)
+        return kwargs
+
+    @async_unsafe
+    def get_new_connection(self, conn_params):
+        return Database.connect(**conn_params)
+
+    def init_connection_state(self):
+        assignments = []
+        if self.features.is_sql_auto_is_null_enabled:
+            # SQL_AUTO_IS_NULL controls whether an AUTO_INCREMENT column on
+            # a recently inserted row will return when the field is tested
+            # for NULL. Disabling this brings this aspect of MySQL in line
+            # with SQL standards.
+            assignments.append('SET SQL_AUTO_IS_NULL = 0')
+
+        if self.isolation_level:
+            assignments.append('SET SESSION TRANSACTION ISOLATION LEVEL %s' % self.isolation_level.upper())
+
+        if assignments:
+            with self.cursor() as cursor:
+                cursor.execute('; '.join(assignments))
+
+    @async_unsafe
+    def create_cursor(self, name=None):
+        cursor = self.connection.cursor()
+        return CursorWrapper(cursor)
+
+    def _rollback(self):
+        try:
+            BaseDatabaseWrapper._rollback(self)
+        except Database.NotSupportedError:
+            pass
+
+    def _set_autocommit(self, autocommit):
+        with self.wrap_database_errors:
+            self.connection.autocommit(autocommit)
+
+    def disable_constraint_checking(self):
+        """
+        Disable foreign key checks, primarily for use in adding rows with
+        forward references. Always return True to indicate constraint checks
+        need to be re-enabled.
+        """
+        self.cursor().execute('SET foreign_key_checks=0')
+        return True
+
+    def enable_constraint_checking(self):
+        """
+        Re-enable foreign key checks after they have been disabled.
+        """
+        # Override needs_rollback in case constraint_checks_disabled is
+        # nested inside transaction.atomic.
+        self.needs_rollback, needs_rollback = False, self.needs_rollback
+        try:
+            self.cursor().execute('SET foreign_key_checks=1')
+        finally:
+            self.needs_rollback = needs_rollback
+
+    def check_constraints(self, table_names=None):
+        """
+        Check each table name in `table_names` for rows with invalid foreign
+        key references. This method is intended to be used in conjunction with
+        `disable_constraint_checking()` and `enable_constraint_checking()`, to
+        determine if rows with invalid references were entered while constraint
+        checks were off.
+        """
+        with self.cursor() as cursor:
+            if table_names is None:
+                table_names = self.introspection.table_names(cursor)
+            for table_name in table_names:
+                primary_key_column_name = self.introspection.get_primary_key_column(cursor, table_name)
+                if not primary_key_column_name:
+                    continue
+                key_columns = self.introspection.get_key_columns(cursor, table_name)
+                for column_name, referenced_table_name, referenced_column_name in key_columns:
+                    cursor.execute(
+                        """
+                        SELECT REFERRING.`%s`, REFERRING.`%s` FROM `%s` as REFERRING
+                        LEFT JOIN `%s` as REFERRED
+                        ON (REFERRING.`%s` = REFERRED.`%s`)
+                        WHERE REFERRING.`%s` IS NOT NULL AND REFERRED.`%s` IS NULL
+                        """ % (
+                            primary_key_column_name, column_name, table_name,
+                            referenced_table_name, column_name, referenced_column_name,
+                            column_name, referenced_column_name,
+                        )
+                    )
+                    for bad_row in cursor.fetchall():
+                        raise utils.IntegrityError(
+                            "The row in table '%s' with primary key '%s' has an invalid "
+                            "foreign key: %s.%s contains a value '%s' that does not "
+                            "have a corresponding value in %s.%s."
+                            % (
+                                table_name, bad_row[0], table_name, column_name,
+                                bad_row[1], referenced_table_name, referenced_column_name,
+                            )
+                        )
+
+    def is_usable(self):
+        try:
+            self.connection.ping()
+        except Database.Error:
+            return False
+        else:
+            return True
+
+    @cached_property
+    def display_name(self):
+        return 'MariaDB' if self.mysql_is_mariadb else 'MySQL'
+
+    @cached_property
+    def data_type_check_constraints(self):
+        if self.features.supports_column_check_constraints:
+            return {
+                'PositiveIntegerField': '`%(column)s` >= 0',
+                'PositiveSmallIntegerField': '`%(column)s` >= 0',
+            }
+        return {}
+
+    @cached_property
+    def mysql_server_info(self):
+        with self.temporary_connection() as cursor:
+            cursor.execute('SELECT VERSION()')
+            return cursor.fetchone()[0]
+
+    @cached_property
+    def mysql_version(self):
+        match = server_version_re.match(self.mysql_server_info)
+        if not match:
+            raise Exception('Unable to determine MySQL version from version string %r' % self.mysql_server_info)
+        return tuple(int(x) for x in match.groups())
+
+    @cached_property
+    def mysql_is_mariadb(self):
+        return 'mariadb' in self.mysql_server_info.lower()

venv/lib/python3.8/site-packages/django/db/backends/mysql/client.py

@@ -0,0 +1,48 @@
+import subprocess
+
+from django.db.backends.base.client import BaseDatabaseClient
+
+
+class DatabaseClient(BaseDatabaseClient):
+    executable_name = 'mysql'
+
+    @classmethod
+    def settings_to_cmd_args(cls, settings_dict):
+        args = [cls.executable_name]
+        db = settings_dict['OPTIONS'].get('db', settings_dict['NAME'])
+        user = settings_dict['OPTIONS'].get('user', settings_dict['USER'])
+        passwd = settings_dict['OPTIONS'].get('passwd', settings_dict['PASSWORD'])
+        host = settings_dict['OPTIONS'].get('host', settings_dict['HOST'])
+        port = settings_dict['OPTIONS'].get('port', settings_dict['PORT'])
+        server_ca = settings_dict['OPTIONS'].get('ssl', {}).get('ca')
+        client_cert = settings_dict['OPTIONS'].get('ssl', {}).get('cert')
+        client_key = settings_dict['OPTIONS'].get('ssl', {}).get('key')
+        defaults_file = settings_dict['OPTIONS'].get('read_default_file')
+        # Seems to be no good way to set sql_mode with CLI.
+
+        if defaults_file:
+            args += ["--defaults-file=%s" % defaults_file]
+        if user:
+            args += ["--user=%s" % user]
+        if passwd:
+            args += ["--password=%s" % passwd]
+        if host:
+            if '/' in host:
+                args += ["--socket=%s" % host]
+            else:
+                args += ["--host=%s" % host]
+        if port:
+            args += ["--port=%s" % port]
+        if server_ca:
+            args += ["--ssl-ca=%s" % server_ca]
+        if client_cert:
+            args += ["--ssl-cert=%s" % client_cert]
+        if client_key:
+            args += ["--ssl-key=%s" % client_key]
+        if db:
+            args += [db]
+        return args
+
+    def runshell(self):
+        args = DatabaseClient.settings_to_cmd_args(self.connection.settings_dict)
+        subprocess.run(args, check=True)

venv/lib/python3.8/site-packages/django/db/backends/mysql/compiler.py

@@ -0,0 +1,25 @@
+from django.db.models.sql import compiler
+
+
+class SQLCompiler(compiler.SQLCompiler):
+    def as_subquery_condition(self, alias, columns, compiler):
+        qn = compiler.quote_name_unless_alias
+        qn2 = self.connection.ops.quote_name
+        sql, params = self.as_sql()
+        return '(%s) IN (%s)' % (', '.join('%s.%s' % (qn(alias), qn2(column)) for column in columns), sql), params
+
+
+class SQLInsertCompiler(compiler.SQLInsertCompiler, SQLCompiler):
+    pass
+
+
+class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler):
+    pass
+
+
+class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler):
+    pass
+
+
+class SQLAggregateCompiler(compiler.SQLAggregateCompiler, SQLCompiler):
+    pass

venv/lib/python3.8/site-packages/django/db/backends/mysql/creation.py

@@ -0,0 +1,66 @@
+import subprocess
+import sys
+
+from django.db.backends.base.creation import BaseDatabaseCreation
+
+from .client import DatabaseClient
+
+
+class DatabaseCreation(BaseDatabaseCreation):
+
+    def sql_table_creation_suffix(self):
+        suffix = []
+        test_settings = self.connection.settings_dict['TEST']
+        if test_settings['CHARSET']:
+            suffix.append('CHARACTER SET %s' % test_settings['CHARSET'])
+        if test_settings['COLLATION']:
+            suffix.append('COLLATE %s' % test_settings['COLLATION'])
+        return ' '.join(suffix)
+
+    def _execute_create_test_db(self, cursor, parameters, keepdb=False):
+        try:
+            super()._execute_create_test_db(cursor, parameters, keepdb)
+        except Exception as e:
+            if len(e.args) < 1 or e.args[0] != 1007:
+                # All errors except "database exists" (1007) cancel tests.
+                self.log('Got an error creating the test database: %s' % e)
+                sys.exit(2)
+            else:
+                raise e
+
+    def _clone_test_db(self, suffix, verbosity, keepdb=False):
+        source_database_name = self.connection.settings_dict['NAME']
+        target_database_name = self.get_test_db_clone_settings(suffix)['NAME']
+        test_db_params = {
+            'dbname': self.connection.ops.quote_name(target_database_name),
+            'suffix': self.sql_table_creation_suffix(),
+        }
+        with self._nodb_connection.cursor() as cursor:
+            try:
+                self._execute_create_test_db(cursor, test_db_params, keepdb)
+            except Exception:
+                if keepdb:
+                    # If the database should be kept, skip everything else.
+                    return
+                try:
+                    if verbosity >= 1:
+                        self.log('Destroying old test database for alias %s...' % (
+                            self._get_database_display_str(verbosity, target_database_name),
+                        ))
+                    cursor.execute('DROP DATABASE %(dbname)s' % test_db_params)
+                    self._execute_create_test_db(cursor, test_db_params, keepdb)
+                except Exception as e:
+                    self.log('Got an error recreating the test database: %s' % e)
+                    sys.exit(2)
+        self._clone_db(source_database_name, target_database_name)
+
+    def _clone_db(self, source_database_name, target_database_name):
+        dump_args = DatabaseClient.settings_to_cmd_args(self.connection.settings_dict)[1:]
+        dump_cmd = ['mysqldump', *dump_args[:-1], '--routines', '--events', source_database_name]
+        load_cmd = DatabaseClient.settings_to_cmd_args(self.connection.settings_dict)
+        load_cmd[-1] = target_database_name
+
+        with subprocess.Popen(dump_cmd, stdout=subprocess.PIPE) as dump_proc:
+            with subprocess.Popen(load_cmd, stdin=dump_proc.stdout, stdout=subprocess.DEVNULL):
+                # Allow dump_proc to receive a SIGPIPE if the load process exits.
+                dump_proc.stdout.close()

venv/lib/python3.8/site-packages/django/db/backends/mysql/features.py

@@ -0,0 +1,138 @@
+import operator
+
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.utils.functional import cached_property
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    empty_fetchmany_value = ()
+    update_can_self_select = False
+    allows_group_by_pk = True
+    related_fields_match_type = True
+    # MySQL doesn't support sliced subqueries with IN/ALL/ANY/SOME.
+    allow_sliced_subqueries_with_in = False
+    has_select_for_update = True
+    supports_forward_references = False
+    supports_regex_backreferencing = False
+    supports_date_lookup_using_string = False
+    can_introspect_autofield = True
+    can_introspect_binary_field = False
+    can_introspect_duration_field = False
+    can_introspect_small_integer_field = True
+    can_introspect_positive_integer_field = True
+    introspected_boolean_field_type = 'IntegerField'
+    supports_index_column_ordering = False
+    supports_timezones = False
+    requires_explicit_null_ordering_when_grouping = True
+    allows_auto_pk_0 = False
+    can_release_savepoints = True
+    atomic_transactions = False
+    can_clone_databases = True
+    supports_temporal_subtraction = True
+    supports_select_intersection = False
+    supports_select_difference = False
+    supports_slicing_ordering_in_compound = True
+    supports_index_on_text_field = False
+    has_case_insensitive_like = False
+    create_test_procedure_without_params_sql = """
+        CREATE PROCEDURE test_procedure ()
+        BEGIN
+            DECLARE V_I INTEGER;
+            SET V_I = 1;
+        END;
+    """
+    create_test_procedure_with_int_param_sql = """
+        CREATE PROCEDURE test_procedure (P_I INTEGER)
+        BEGIN
+            DECLARE V_I INTEGER;
+            SET V_I = P_I;
+        END;
+    """
+    db_functions_convert_bytes_to_str = True
+    # Alias MySQL's TRADITIONAL to TEXT for consistency with other backends.
+    supported_explain_formats = {'JSON', 'TEXT', 'TRADITIONAL'}
+    # Neither MySQL nor MariaDB support partial indexes.
+    supports_partial_indexes = False
+
+    @cached_property
+    def _mysql_storage_engine(self):
+        "Internal method used in Django tests. Don't rely on this from your code"
+        with self.connection.cursor() as cursor:
+            cursor.execute("SELECT ENGINE FROM INFORMATION_SCHEMA.ENGINES WHERE SUPPORT = 'DEFAULT'")
+            result = cursor.fetchone()
+        return result[0]
+
+    @cached_property
+    def can_introspect_foreign_keys(self):
+        "Confirm support for introspected foreign keys"
+        return self._mysql_storage_engine != 'MyISAM'
+
+    @cached_property
+    def has_zoneinfo_database(self):
+        # Test if the time zone definitions are installed. CONVERT_TZ returns
+        # NULL if 'UTC' timezone isn't loaded into the mysql.time_zone.
+        with self.connection.cursor() as cursor:
+            cursor.execute("SELECT CONVERT_TZ('2001-01-01 01:00:00', 'UTC', 'UTC')")
+            return cursor.fetchone()[0] is not None
+
+    @cached_property
+    def is_sql_auto_is_null_enabled(self):
+        with self.connection.cursor() as cursor:
+            cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
+            result = cursor.fetchone()
+            return result and result[0] == 1
+
+    @cached_property
+    def supports_over_clause(self):
+        if self.connection.mysql_is_mariadb:
+            return self.connection.mysql_version >= (10, 2)
+        return self.connection.mysql_version >= (8, 0, 2)
+
+    @cached_property
+    def supports_column_check_constraints(self):
+        if self.connection.mysql_is_mariadb:
+            return self.connection.mysql_version >= (10, 2, 1)
+        return self.connection.mysql_version >= (8, 0, 16)
+
+    supports_table_check_constraints = property(operator.attrgetter('supports_column_check_constraints'))
+
+    @cached_property
+    def can_introspect_check_constraints(self):
+        if self.connection.mysql_is_mariadb:
+            version = self.connection.mysql_version
+            return (version >= (10, 2, 22) and version < (10, 3)) or version >= (10, 3, 10)
+        return self.connection.mysql_version >= (8, 0, 16)
+
+    @cached_property
+    def has_select_for_update_skip_locked(self):
+        return not self.connection.mysql_is_mariadb and self.connection.mysql_version >= (8, 0, 1)
+
+    @cached_property
+    def has_select_for_update_nowait(self):
+        if self.connection.mysql_is_mariadb:
+            return self.connection.mysql_version >= (10, 3, 0)
+        return self.connection.mysql_version >= (8, 0, 1)
+
+    @cached_property
+    def needs_explain_extended(self):
+        # EXTENDED is deprecated (and not required) in MySQL 5.7.
+        return not self.connection.mysql_is_mariadb and self.connection.mysql_version < (5, 7)
+
+    @cached_property
+    def supports_transactions(self):
+        """
+        All storage engines except MyISAM support transactions.
+        """
+        return self._mysql_storage_engine != 'MyISAM'
+
+    @cached_property
+    def ignores_table_name_case(self):
+        with self.connection.cursor() as cursor:
+            cursor.execute('SELECT @@LOWER_CASE_TABLE_NAMES')
+            result = cursor.fetchone()
+            return result and result[0] != 0
+
+    @cached_property
+    def supports_default_in_lead_lag(self):
+        # To be added in https://jira.mariadb.org/browse/MDEV-12981.
+        return not self.connection.mysql_is_mariadb

venv/lib/python3.8/site-packages/django/db/backends/mysql/introspection.py

@@ -0,0 +1,267 @@
+from collections import namedtuple
+
+import sqlparse
+from MySQLdb.constants import FIELD_TYPE
+
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo as BaseFieldInfo, TableInfo,
+)
+from django.db.models.indexes import Index
+from django.utils.datastructures import OrderedSet
+
+FieldInfo = namedtuple('FieldInfo', BaseFieldInfo._fields + ('extra', 'is_unsigned'))
+InfoLine = namedtuple('InfoLine', 'col_name data_type max_len num_prec num_scale extra column_default is_unsigned')
+
+
+class DatabaseIntrospection(BaseDatabaseIntrospection):
+    data_types_reverse = {
+        FIELD_TYPE.BLOB: 'TextField',
+        FIELD_TYPE.CHAR: 'CharField',
+        FIELD_TYPE.DECIMAL: 'DecimalField',
+        FIELD_TYPE.NEWDECIMAL: 'DecimalField',
+        FIELD_TYPE.DATE: 'DateField',
+        FIELD_TYPE.DATETIME: 'DateTimeField',
+        FIELD_TYPE.DOUBLE: 'FloatField',
+        FIELD_TYPE.FLOAT: 'FloatField',
+        FIELD_TYPE.INT24: 'IntegerField',
+        FIELD_TYPE.LONG: 'IntegerField',
+        FIELD_TYPE.LONGLONG: 'BigIntegerField',
+        FIELD_TYPE.SHORT: 'SmallIntegerField',
+        FIELD_TYPE.STRING: 'CharField',
+        FIELD_TYPE.TIME: 'TimeField',
+        FIELD_TYPE.TIMESTAMP: 'DateTimeField',
+        FIELD_TYPE.TINY: 'IntegerField',
+        FIELD_TYPE.TINY_BLOB: 'TextField',
+        FIELD_TYPE.MEDIUM_BLOB: 'TextField',
+        FIELD_TYPE.LONG_BLOB: 'TextField',
+        FIELD_TYPE.VAR_STRING: 'CharField',
+    }
+
+    def get_field_type(self, data_type, description):
+        field_type = super().get_field_type(data_type, description)
+        if 'auto_increment' in description.extra:
+            if field_type == 'IntegerField':
+                return 'AutoField'
+            elif field_type == 'BigIntegerField':
+                return 'BigAutoField'
+            elif field_type == 'SmallIntegerField':
+                return 'SmallAutoField'
+        if description.is_unsigned:
+            if field_type == 'IntegerField':
+                return 'PositiveIntegerField'
+            elif field_type == 'SmallIntegerField':
+                return 'PositiveSmallIntegerField'
+        return field_type
+
+    def get_table_list(self, cursor):
+        """Return a list of table and view names in the current database."""
+        cursor.execute("SHOW FULL TABLES")
+        return [TableInfo(row[0], {'BASE TABLE': 't', 'VIEW': 'v'}.get(row[1]))
+                for row in cursor.fetchall()]
+
+    def get_table_description(self, cursor, table_name):
+        """
+        Return a description of the table with the DB-API cursor.description
+        interface."
+        """
+        # information_schema database gives more accurate results for some figures:
+        # - varchar length returned by cursor.description is an internal length,
+        #   not visible length (#5725)
+        # - precision and scale (for decimal fields) (#5014)
+        # - auto_increment is not available in cursor.description
+        cursor.execute("""
+            SELECT
+                column_name, data_type, character_maximum_length,
+                numeric_precision, numeric_scale, extra, column_default,
+                CASE
+                    WHEN column_type LIKE '%% unsigned' THEN 1
+                    ELSE 0
+                END AS is_unsigned
+            FROM information_schema.columns
+            WHERE table_name = %s AND table_schema = DATABASE()""", [table_name])
+        field_info = {line[0]: InfoLine(*line) for line in cursor.fetchall()}
+
+        cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
+
+        def to_int(i):
+            return int(i) if i is not None else i
+
+        fields = []
+        for line in cursor.description:
+            info = field_info[line[0]]
+            fields.append(FieldInfo(
+                *line[:3],
+                to_int(info.max_len) or line[3],
+                to_int(info.num_prec) or line[4],
+                to_int(info.num_scale) or line[5],
+                line[6],
+                info.column_default,
+                info.extra,
+                info.is_unsigned,
+            ))
+        return fields
+
+    def get_sequences(self, cursor, table_name, table_fields=()):
+        for field_info in self.get_table_description(cursor, table_name):
+            if 'auto_increment' in field_info.extra:
+                # MySQL allows only one auto-increment column per table.
+                return [{'table': table_name, 'column': field_info.name}]
+        return []
+
+    def get_relations(self, cursor, table_name):
+        """
+        Return a dictionary of {field_name: (field_name_other_table, other_table)}
+        representing all relationships to the given table.
+        """
+        constraints = self.get_key_columns(cursor, table_name)
+        relations = {}
+        for my_fieldname, other_table, other_field in constraints:
+            relations[my_fieldname] = (other_field, other_table)
+        return relations
+
+    def get_key_columns(self, cursor, table_name):
+        """
+        Return a list of (column_name, referenced_table_name, referenced_column_name)
+        for all key columns in the given table.
+        """
+        key_columns = []
+        cursor.execute("""
+            SELECT column_name, referenced_table_name, referenced_column_name
+            FROM information_schema.key_column_usage
+            WHERE table_name = %s
+                AND table_schema = DATABASE()
+                AND referenced_table_name IS NOT NULL
+                AND referenced_column_name IS NOT NULL""", [table_name])
+        key_columns.extend(cursor.fetchall())
+        return key_columns
+
+    def get_storage_engine(self, cursor, table_name):
+        """
+        Retrieve the storage engine for a given table. Return the default
+        storage engine if the table doesn't exist.
+        """
+        cursor.execute(
+            "SELECT engine "
+            "FROM information_schema.tables "
+            "WHERE table_name = %s", [table_name])
+        result = cursor.fetchone()
+        if not result:
+            return self.connection.features._mysql_storage_engine
+        return result[0]
+
+    def _parse_constraint_columns(self, check_clause, columns):
+        check_columns = OrderedSet()
+        statement = sqlparse.parse(check_clause)[0]
+        tokens = (token for token in statement.flatten() if not token.is_whitespace)
+        for token in tokens:
+            if (
+                token.ttype == sqlparse.tokens.Name and
+                self.connection.ops.quote_name(token.value) == token.value and
+                token.value[1:-1] in columns
+            ):
+                check_columns.add(token.value[1:-1])
+        return check_columns
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieve any constraints or keys (unique, pk, fk, check, index) across
+        one or more columns.
+        """
+        constraints = {}
+        # Get the actual constraint names and columns
+        name_query = """
+            SELECT kc.`constraint_name`, kc.`column_name`,
+                kc.`referenced_table_name`, kc.`referenced_column_name`
+            FROM information_schema.key_column_usage AS kc
+            WHERE
+                kc.table_schema = DATABASE() AND
+                kc.table_name = %s
+            ORDER BY kc.`ordinal_position`
+        """
+        cursor.execute(name_query, [table_name])
+        for constraint, column, ref_table, ref_column in cursor.fetchall():
+            if constraint not in constraints:
+                constraints[constraint] = {
+                    'columns': OrderedSet(),
+                    'primary_key': False,
+                    'unique': False,
+                    'index': False,
+                    'check': False,
+                    'foreign_key': (ref_table, ref_column) if ref_column else None,
+                }
+            constraints[constraint]['columns'].add(column)
+        # Now get the constraint types
+        type_query = """
+            SELECT c.constraint_name, c.constraint_type
+            FROM information_schema.table_constraints AS c
+            WHERE
+                c.table_schema = DATABASE() AND
+                c.table_name = %s
+        """
+        cursor.execute(type_query, [table_name])
+        for constraint, kind in cursor.fetchall():
+            if kind.lower() == "primary key":
+                constraints[constraint]['primary_key'] = True
+                constraints[constraint]['unique'] = True
+            elif kind.lower() == "unique":
+                constraints[constraint]['unique'] = True
+        # Add check constraints.
+        if self.connection.features.can_introspect_check_constraints:
+            unnamed_constraints_index = 0
+            columns = {info.name for info in self.get_table_description(cursor, table_name)}
+            if self.connection.mysql_is_mariadb:
+                type_query = """
+                    SELECT c.constraint_name, c.check_clause
+                    FROM information_schema.check_constraints AS c
+                    WHERE
+                        c.constraint_schema = DATABASE() AND
+                        c.table_name = %s
+                """
+            else:
+                type_query = """
+                    SELECT cc.constraint_name, cc.check_clause
+                    FROM
+                        information_schema.check_constraints AS cc,
+                        information_schema.table_constraints AS tc
+                    WHERE
+                        cc.constraint_schema = DATABASE() AND
+                        tc.table_schema = cc.constraint_schema AND
+                        cc.constraint_name = tc.constraint_name AND
+                        tc.constraint_type = 'CHECK' AND
+                        tc.table_name = %s
+                """
+            cursor.execute(type_query, [table_name])
+            for constraint, check_clause in cursor.fetchall():
+                constraint_columns = self._parse_constraint_columns(check_clause, columns)
+                # Ensure uniqueness of unnamed constraints. Unnamed unique
+                # and check columns constraints have the same name as
+                # a column.
+                if set(constraint_columns) == {constraint}:
+                    unnamed_constraints_index += 1
+                    constraint = '__unnamed_constraint_%s__' % unnamed_constraints_index
+                constraints[constraint] = {
+                    'columns': constraint_columns,
+                    'primary_key': False,
+                    'unique': False,
+                    'index': False,
+                    'check': True,
+                    'foreign_key': None,
+                }
+        # Now add in the indexes
+        cursor.execute("SHOW INDEX FROM %s" % self.connection.ops.quote_name(table_name))
+        for table, non_unique, index, colseq, column, type_ in [x[:5] + (x[10],) for x in cursor.fetchall()]:
+            if index not in constraints:
+                constraints[index] = {
+                    'columns': OrderedSet(),
+                    'primary_key': False,
+                    'unique': False,
+                    'check': False,
+                    'foreign_key': None,
+                }
+            constraints[index]['index'] = True
+            constraints[index]['type'] = Index.suffix if type_ == 'BTREE' else type_.lower()
+            constraints[index]['columns'].add(column)
+        # Convert the sorted sets to lists
+        for constraint in constraints.values():
+            constraint['columns'] = list(constraint['columns'])
+        return constraints

venv/lib/python3.8/site-packages/django/db/backends/mysql/operations.py

@@ -0,0 +1,317 @@
+import uuid
+
+from django.conf import settings
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.utils import timezone
+from django.utils.duration import duration_microseconds
+from django.utils.encoding import force_str
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    compiler_module = "django.db.backends.mysql.compiler"
+
+    # MySQL stores positive fields as UNSIGNED ints.
+    integer_field_ranges = {
+        **BaseDatabaseOperations.integer_field_ranges,
+        'PositiveSmallIntegerField': (0, 65535),
+        'PositiveIntegerField': (0, 4294967295),
+    }
+    cast_data_types = {
+        'AutoField': 'signed integer',
+        'BigAutoField': 'signed integer',
+        'SmallAutoField': 'signed integer',
+        'CharField': 'char(%(max_length)s)',
+        'DecimalField': 'decimal(%(max_digits)s, %(decimal_places)s)',
+        'TextField': 'char',
+        'IntegerField': 'signed integer',
+        'BigIntegerField': 'signed integer',
+        'SmallIntegerField': 'signed integer',
+        'PositiveIntegerField': 'unsigned integer',
+        'PositiveSmallIntegerField': 'unsigned integer',
+    }
+    cast_char_field_without_max_length = 'char'
+    explain_prefix = 'EXPLAIN'
+
+    def date_extract_sql(self, lookup_type, field_name):
+        # https://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
+        if lookup_type == 'week_day':
+            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
+            # Note: WEEKDAY() returns 0-6, Monday=0.
+            return "DAYOFWEEK(%s)" % field_name
+        elif lookup_type == 'week':
+            # Override the value of default_week_format for consistency with
+            # other database backends.
+            # Mode 3: Monday, 1-53, with 4 or more days this year.
+            return "WEEK(%s, 3)" % field_name
+        elif lookup_type == 'iso_year':
+            # Get the year part from the YEARWEEK function, which returns a
+            # number as year * 100 + week.
+            return "TRUNCATE(YEARWEEK(%s, 3), -2) / 100" % field_name
+        else:
+            # EXTRACT returns 1-53 based on ISO-8601 for the week number.
+            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        fields = {
+            'year': '%%Y-01-01',
+            'month': '%%Y-%%m-01',
+        }  # Use double percents to escape.
+        if lookup_type in fields:
+            format_str = fields[lookup_type]
+            return "CAST(DATE_FORMAT(%s, '%s') AS DATE)" % (field_name, format_str)
+        elif lookup_type == 'quarter':
+            return "MAKEDATE(YEAR(%s), 1) + INTERVAL QUARTER(%s) QUARTER - INTERVAL 1 QUARTER" % (
+                field_name, field_name
+            )
+        elif lookup_type == 'week':
+            return "DATE_SUB(%s, INTERVAL WEEKDAY(%s) DAY)" % (
+                field_name, field_name
+            )
+        else:
+            return "DATE(%s)" % (field_name)
+
+    def _prepare_tzname_delta(self, tzname):
+        if '+' in tzname:
+            return tzname[tzname.find('+'):]
+        elif '-' in tzname:
+            return tzname[tzname.find('-'):]
+        return tzname
+
+    def _convert_field_to_tz(self, field_name, tzname):
+        if settings.USE_TZ and self.connection.timezone_name != tzname:
+            field_name = "CONVERT_TZ(%s, '%s', '%s')" % (
+                field_name,
+                self.connection.timezone_name,
+                self._prepare_tzname_delta(tzname),
+            )
+        return field_name
+
+    def datetime_cast_date_sql(self, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return "DATE(%s)" % field_name
+
+    def datetime_cast_time_sql(self, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return "TIME(%s)" % field_name
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return self.date_extract_sql(lookup_type, field_name)
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
+        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
+        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
+        if lookup_type == 'quarter':
+            return (
+                "CAST(DATE_FORMAT(MAKEDATE(YEAR({field_name}), 1) + "
+                "INTERVAL QUARTER({field_name}) QUARTER - " +
+                "INTERVAL 1 QUARTER, '%%Y-%%m-01 00:00:00') AS DATETIME)"
+            ).format(field_name=field_name)
+        if lookup_type == 'week':
+            return (
+                "CAST(DATE_FORMAT(DATE_SUB({field_name}, "
+                "INTERVAL WEEKDAY({field_name}) DAY), "
+                "'%%Y-%%m-%%d 00:00:00') AS DATETIME)"
+            ).format(field_name=field_name)
+        try:
+            i = fields.index(lookup_type) + 1
+        except ValueError:
+            sql = field_name
+        else:
+            format_str = ''.join(format[:i] + format_def[i:])
+            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
+        return sql
+
+    def time_trunc_sql(self, lookup_type, field_name):
+        fields = {
+            'hour': '%%H:00:00',
+            'minute': '%%H:%%i:00',
+            'second': '%%H:%%i:%%s',
+        }  # Use double percents to escape.
+        if lookup_type in fields:
+            format_str = fields[lookup_type]
+            return "CAST(DATE_FORMAT(%s, '%s') AS TIME)" % (field_name, format_str)
+        else:
+            return "TIME(%s)" % (field_name)
+
+    def date_interval_sql(self, timedelta):
+        return 'INTERVAL %s MICROSECOND' % duration_microseconds(timedelta)
+
+    def format_for_duration_arithmetic(self, sql):
+        return 'INTERVAL %s MICROSECOND' % sql
+
+    def force_no_ordering(self):
+        """
+        "ORDER BY NULL" prevents MySQL from implicitly ordering by grouped
+        columns. If no ordering would otherwise be applied, we don't want any
+        implicit sorting going on.
+        """
+        return [(None, ("NULL", [], False))]
+
+    def last_executed_query(self, cursor, sql, params):
+        # With MySQLdb, cursor objects have an (undocumented) "_executed"
+        # attribute where the exact query sent to the database is saved.
+        # See MySQLdb/cursors.py in the source distribution.
+        # MySQLdb returns string, PyMySQL bytes.
+        return force_str(getattr(cursor, '_executed', None), errors='replace')
+
+    def no_limit_value(self):
+        # 2**64 - 1, as recommended by the MySQL documentation
+        return 18446744073709551615
+
+    def quote_name(self, name):
+        if name.startswith("`") and name.endswith("`"):
+            return name  # Quoting once is enough.
+        return "`%s`" % name
+
+    def random_function_sql(self):
+        return 'RAND()'
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        # NB: The generated SQL below is specific to MySQL
+        # 'TRUNCATE x;', 'TRUNCATE y;', 'TRUNCATE z;'... style SQL statements
+        # to clear all tables of all data
+        if tables:
+            sql = ['SET FOREIGN_KEY_CHECKS = 0;']
+            for table in tables:
+                sql.append('%s %s;' % (
+                    style.SQL_KEYWORD('TRUNCATE'),
+                    style.SQL_FIELD(self.quote_name(table)),
+                ))
+            sql.append('SET FOREIGN_KEY_CHECKS = 1;')
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+            return sql
+        else:
+            return []
+
+    def validate_autopk_value(self, value):
+        # MySQLism: zero in AUTO_INCREMENT field does not work. Refs #17653.
+        if value == 0:
+            raise ValueError('The database backend does not accept 0 as a '
+                             'value for AutoField.')
+        return value
+
+    def adapt_datetimefield_value(self, value):
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, 'resolve_expression'):
+            return value
+
+        # MySQL doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = timezone.make_naive(value, self.connection.timezone)
+            else:
+                raise ValueError("MySQL backend does not support timezone-aware datetimes when USE_TZ is False.")
+        return str(value)
+
+    def adapt_timefield_value(self, value):
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, 'resolve_expression'):
+            return value
+
+        # MySQL doesn't support tz-aware times
+        if timezone.is_aware(value):
+            raise ValueError("MySQL backend does not support timezone-aware times.")
+
+        return str(value)
+
+    def max_name_length(self):
+        return 64
+
+    def bulk_insert_sql(self, fields, placeholder_rows):
+        placeholder_rows_sql = (", ".join(row) for row in placeholder_rows)
+        values_sql = ", ".join("(%s)" % sql for sql in placeholder_rows_sql)
+        return "VALUES " + values_sql
+
+    def combine_expression(self, connector, sub_expressions):
+        if connector == '^':
+            return 'POW(%s)' % ','.join(sub_expressions)
+        # Convert the result to a signed integer since MySQL's binary operators
+        # return an unsigned integer.
+        elif connector in ('&', '|', '<<'):
+            return 'CONVERT(%s, SIGNED)' % connector.join(sub_expressions)
+        elif connector == '>>':
+            lhs, rhs = sub_expressions
+            return 'FLOOR(%(lhs)s / POW(2, %(rhs)s))' % {'lhs': lhs, 'rhs': rhs}
+        return super().combine_expression(connector, sub_expressions)
+
+    def get_db_converters(self, expression):
+        converters = super().get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type in ['BooleanField', 'NullBooleanField']:
+            converters.append(self.convert_booleanfield_value)
+        elif internal_type == 'DateTimeField':
+            if settings.USE_TZ:
+                converters.append(self.convert_datetimefield_value)
+        elif internal_type == 'UUIDField':
+            converters.append(self.convert_uuidfield_value)
+        return converters
+
+    def convert_booleanfield_value(self, value, expression, connection):
+        if value in (0, 1):
+            value = bool(value)
+        return value
+
+    def convert_datetimefield_value(self, value, expression, connection):
+        if value is not None:
+            value = timezone.make_aware(value, self.connection.timezone)
+        return value
+
+    def convert_uuidfield_value(self, value, expression, connection):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    def binary_placeholder_sql(self, value):
+        return '_binary %s' if value is not None and not hasattr(value, 'as_sql') else '%s'
+
+    def subtract_temporals(self, internal_type, lhs, rhs):
+        lhs_sql, lhs_params = lhs
+        rhs_sql, rhs_params = rhs
+        if internal_type == 'TimeField':
+            if self.connection.mysql_is_mariadb:
+                # MariaDB includes the microsecond component in TIME_TO_SEC as
+                # a decimal. MySQL returns an integer without microseconds.
+                return 'CAST((TIME_TO_SEC(%(lhs)s) - TIME_TO_SEC(%(rhs)s)) * 1000000 AS SIGNED)' % {
+                    'lhs': lhs_sql, 'rhs': rhs_sql
+                }, (*lhs_params, *rhs_params)
+            return (
+                "((TIME_TO_SEC(%(lhs)s) * 1000000 + MICROSECOND(%(lhs)s)) -"
+                " (TIME_TO_SEC(%(rhs)s) * 1000000 + MICROSECOND(%(rhs)s)))"
+            ) % {'lhs': lhs_sql, 'rhs': rhs_sql}, tuple(lhs_params) * 2 + tuple(rhs_params) * 2
+        params = (*rhs_params, *lhs_params)
+        return "TIMESTAMPDIFF(MICROSECOND, %s, %s)" % (rhs_sql, lhs_sql), params
+
+    def explain_query_prefix(self, format=None, **options):
+        # Alias MySQL's TRADITIONAL to TEXT for consistency with other backends.
+        if format and format.upper() == 'TEXT':
+            format = 'TRADITIONAL'
+        prefix = super().explain_query_prefix(format, **options)
+        if format:
+            prefix += ' FORMAT=%s' % format
+        if self.connection.features.needs_explain_extended and format is None:
+            # EXTENDED and FORMAT are mutually exclusive options.
+            prefix += ' EXTENDED'
+        return prefix
+
+    def regex_lookup(self, lookup_type):
+        # REGEXP BINARY doesn't work correctly in MySQL 8+ and REGEXP_LIKE
+        # doesn't exist in MySQL 5.6 or in MariaDB.
+        if self.connection.mysql_version < (8, 0, 0) or self.connection.mysql_is_mariadb:
+            if lookup_type == 'regex':
+                return '%s REGEXP BINARY %s'
+            return '%s REGEXP %s'
+
+        match_option = 'c' if lookup_type == 'regex' else 'i'
+        return "REGEXP_LIKE(%%s, %%s, '%s')" % match_option
+
+    def insert_statement(self, ignore_conflicts=False):
+        return 'INSERT IGNORE INTO' if ignore_conflicts else super().insert_statement(ignore_conflicts)

venv/lib/python3.8/site-packages/django/db/backends/mysql/schema.py

@@ -0,0 +1,139 @@
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.models import NOT_PROVIDED
+
+
+class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
+
+    sql_rename_table = "RENAME TABLE %(old_table)s TO %(new_table)s"
+
+    sql_alter_column_null = "MODIFY %(column)s %(type)s NULL"
+    sql_alter_column_not_null = "MODIFY %(column)s %(type)s NOT NULL"
+    sql_alter_column_type = "MODIFY %(column)s %(type)s"
+
+    # No 'CASCADE' which works as a no-op in MySQL but is undocumented
+    sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
+
+    sql_rename_column = "ALTER TABLE %(table)s CHANGE %(old_column)s %(new_column)s %(type)s"
+
+    sql_delete_unique = "ALTER TABLE %(table)s DROP INDEX %(name)s"
+    sql_create_column_inline_fk = (
+        ', ADD CONSTRAINT %(name)s FOREIGN KEY (%(column)s) '
+        'REFERENCES %(to_table)s(%(to_column)s)'
+    )
+    sql_delete_fk = "ALTER TABLE %(table)s DROP FOREIGN KEY %(name)s"
+
+    sql_delete_index = "DROP INDEX %(name)s ON %(table)s"
+
+    sql_create_pk = "ALTER TABLE %(table)s ADD CONSTRAINT %(name)s PRIMARY KEY (%(columns)s)"
+    sql_delete_pk = "ALTER TABLE %(table)s DROP PRIMARY KEY"
+
+    sql_create_index = 'CREATE INDEX %(name)s ON %(table)s (%(columns)s)%(extra)s'
+
+    @property
+    def sql_delete_check(self):
+        if self.connection.mysql_is_mariadb:
+            # The name of the column check constraint is the same as the field
+            # name on MariaDB. Adding IF EXISTS clause prevents migrations
+            # crash. Constraint is removed during a "MODIFY" column statement.
+            return 'ALTER TABLE %(table)s DROP CONSTRAINT IF EXISTS %(name)s'
+        return 'ALTER TABLE %(table)s DROP CHECK %(name)s'
+
+    def quote_value(self, value):
+        self.connection.ensure_connection()
+        if isinstance(value, str):
+            value = value.replace('%', '%%')
+        # MySQLdb escapes to string, PyMySQL to bytes.
+        quoted = self.connection.connection.escape(value, self.connection.connection.encoders)
+        if isinstance(value, str) and isinstance(quoted, bytes):
+            quoted = quoted.decode()
+        return quoted
+
+    def _is_limited_data_type(self, field):
+        db_type = field.db_type(self.connection)
+        return db_type is not None and db_type.lower() in self.connection._limited_data_types
+
+    def skip_default(self, field):
+        if not self._supports_limited_data_type_defaults:
+            return self._is_limited_data_type(field)
+        return False
+
+    @property
+    def _supports_limited_data_type_defaults(self):
+        # MariaDB >= 10.2.1 and MySQL >= 8.0.13 supports defaults for BLOB
+        # and TEXT.
+        if self.connection.mysql_is_mariadb:
+            return self.connection.mysql_version >= (10, 2, 1)
+        return self.connection.mysql_version >= (8, 0, 13)
+
+    def _column_default_sql(self, field):
+        if (
+            not self.connection.mysql_is_mariadb and
+            self._supports_limited_data_type_defaults and
+            self._is_limited_data_type(field)
+        ):
+            # MySQL supports defaults for BLOB and TEXT columns only if the
+            # default value is written as an expression i.e. in parentheses.
+            return '(%s)'
+        return super()._column_default_sql(field)
+
+    def add_field(self, model, field):
+        super().add_field(model, field)
+
+        # Simulate the effect of a one-off default.
+        # field.default may be unhashable, so a set isn't used for "in" check.
+        if self.skip_default(field) and field.default not in (None, NOT_PROVIDED):
+            effective_default = self.effective_default(field)
+            self.execute('UPDATE %(table)s SET %(column)s = %%s' % {
+                'table': self.quote_name(model._meta.db_table),
+                'column': self.quote_name(field.column),
+            }, [effective_default])
+
+    def _field_should_be_indexed(self, model, field):
+        create_index = super()._field_should_be_indexed(model, field)
+        storage = self.connection.introspection.get_storage_engine(
+            self.connection.cursor(), model._meta.db_table
+        )
+        # No need to create an index for ForeignKey fields except if
+        # db_constraint=False because the index from that constraint won't be
+        # created.
+        if (storage == "InnoDB" and
+                create_index and
+                field.get_internal_type() == 'ForeignKey' and
+                field.db_constraint):
+            return False
+        return not self._is_limited_data_type(field) and create_index
+
+    def _delete_composed_index(self, model, fields, *args):
+        """
+        MySQL can remove an implicit FK index on a field when that field is
+        covered by another index like a unique_together. "covered" here means
+        that the more complex index starts like the simpler one.
+        http://bugs.mysql.com/bug.php?id=37910 / Django ticket #24757
+        We check here before removing the [unique|index]_together if we have to
+        recreate a FK index.
+        """
+        first_field = model._meta.get_field(fields[0])
+        if first_field.get_internal_type() == 'ForeignKey':
+            constraint_names = self._constraint_names(model, [first_field.column], index=True)
+            if not constraint_names:
+                self.execute(self._create_index_sql(model, [first_field], suffix=""))
+        return super()._delete_composed_index(model, fields, *args)
+
+    def _set_field_new_type_null_status(self, field, new_type):
+        """
+        Keep the null property of the old field. If it has changed, it will be
+        handled separately.
+        """
+        if field.null:
+            new_type += " NULL"
+        else:
+            new_type += " NOT NULL"
+        return new_type
+
+    def _alter_column_type_sql(self, model, old_field, new_field, new_type):
+        new_type = self._set_field_new_type_null_status(old_field, new_type)
+        return super()._alter_column_type_sql(model, old_field, new_field, new_type)
+
+    def _rename_field_sql(self, table, old_field, new_field, new_type):
+        new_type = self._set_field_new_type_null_status(old_field, new_type)
+        return super()._rename_field_sql(table, old_field, new_field, new_type)

venv/lib/python3.8/site-packages/django/db/backends/mysql/validation.py

@@ -0,0 +1,60 @@
+from django.core import checks
+from django.db.backends.base.validation import BaseDatabaseValidation
+from django.utils.version import get_docs_version
+
+
+class DatabaseValidation(BaseDatabaseValidation):
+    def check(self, **kwargs):
+        issues = super().check(**kwargs)
+        issues.extend(self._check_sql_mode(**kwargs))
+        return issues
+
+    def _check_sql_mode(self, **kwargs):
+        with self.connection.cursor() as cursor:
+            cursor.execute("SELECT @@sql_mode")
+            sql_mode = cursor.fetchone()
+        modes = set(sql_mode[0].split(',') if sql_mode else ())
+        if not (modes & {'STRICT_TRANS_TABLES', 'STRICT_ALL_TABLES'}):
+            return [checks.Warning(
+                "MySQL Strict Mode is not set for database connection '%s'" % self.connection.alias,
+                hint="MySQL's Strict Mode fixes many data integrity problems in MySQL, "
+                     "such as data truncation upon insertion, by escalating warnings into "
+                     "errors. It is strongly recommended you activate it. See: "
+                     "https://docs.djangoproject.com/en/%s/ref/databases/#mysql-sql-mode"
+                     % (get_docs_version(),),
+                id='mysql.W002',
+            )]
+        return []
+
+    def check_field_type(self, field, field_type):
+        """
+        MySQL has the following field length restriction:
+        No character (varchar) fields can have a length exceeding 255
+        characters if they have a unique index on them.
+        MySQL doesn't support a database index on some data types.
+        """
+        errors = []
+        if (field_type.startswith('varchar') and field.unique and
+                (field.max_length is None or int(field.max_length) > 255)):
+            errors.append(
+                checks.Error(
+                    'MySQL does not allow unique CharFields to have a max_length > 255.',
+                    obj=field,
+                    id='mysql.E001',
+                )
+            )
+
+        if field.db_index and field_type.lower() in self.connection._limited_data_types:
+            errors.append(
+                checks.Warning(
+                    '%s does not support a database index on %s columns.'
+                    % (self.connection.display_name, field_type),
+                    hint=(
+                        "An index won't be created. Silence this warning if "
+                        "you don't care about it."
+                    ),
+                    obj=field,
+                    id='fields.W162',
+                )
+            )
+        return errors

venv/lib/python3.8/site-packages/django/db/backends/oracle/base.py

@@ -0,0 +1,550 @@
+"""
+Oracle database backend for Django.
+
+Requires cx_Oracle: https://oracle.github.io/python-cx_Oracle/
+"""
+import datetime
+import decimal
+import os
+import platform
+from contextlib import contextmanager
+
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.db import utils
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.utils.asyncio import async_unsafe
+from django.utils.encoding import force_bytes, force_str
+from django.utils.functional import cached_property
+
+
+def _setup_environment(environ):
+    # Cygwin requires some special voodoo to set the environment variables
+    # properly so that Oracle will see them.
+    if platform.system().upper().startswith('CYGWIN'):
+        try:
+            import ctypes
+        except ImportError as e:
+            raise ImproperlyConfigured("Error loading ctypes: %s; "
+                                       "the Oracle backend requires ctypes to "
+                                       "operate correctly under Cygwin." % e)
+        kernel32 = ctypes.CDLL('kernel32')
+        for name, value in environ:
+            kernel32.SetEnvironmentVariableA(name, value)
+    else:
+        os.environ.update(environ)
+
+
+_setup_environment([
+    # Oracle takes client-side character set encoding from the environment.
+    ('NLS_LANG', '.AL32UTF8'),
+    # This prevents unicode from getting mangled by getting encoded into the
+    # potentially non-unicode database character set.
+    ('ORA_NCHAR_LITERAL_REPLACE', 'TRUE'),
+])
+
+
+try:
+    import cx_Oracle as Database
+except ImportError as e:
+    raise ImproperlyConfigured("Error loading cx_Oracle module: %s" % e)
+
+# Some of these import cx_Oracle, so import them after checking if it's installed.
+from .client import DatabaseClient                          # NOQA isort:skip
+from .creation import DatabaseCreation                      # NOQA isort:skip
+from .features import DatabaseFeatures                      # NOQA isort:skip
+from .introspection import DatabaseIntrospection            # NOQA isort:skip
+from .operations import DatabaseOperations                  # NOQA isort:skip
+from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
+from .utils import Oracle_datetime                          # NOQA isort:skip
+from .validation import DatabaseValidation                  # NOQA isort:skip
+
+
+@contextmanager
+def wrap_oracle_errors():
+    try:
+        yield
+    except Database.DatabaseError as e:
+        # cx_Oracle raises a cx_Oracle.DatabaseError exception with the
+        # following attributes and values:
+        #  code = 2091
+        #  message = 'ORA-02091: transaction rolled back
+        #            'ORA-02291: integrity constraint (TEST_DJANGOTEST.SYS
+        #               _C00102056) violated - parent key not found'
+        # Convert that case to Django's IntegrityError exception.
+        x = e.args[0]
+        if hasattr(x, 'code') and hasattr(x, 'message') and x.code == 2091 and 'ORA-02291' in x.message:
+            raise utils.IntegrityError(*tuple(e.args))
+        raise
+
+
+class _UninitializedOperatorsDescriptor:
+
+    def __get__(self, instance, cls=None):
+        # If connection.operators is looked up before a connection has been
+        # created, transparently initialize connection.operators to avert an
+        # AttributeError.
+        if instance is None:
+            raise AttributeError("operators not available as class attribute")
+        # Creating a cursor will initialize the operators.
+        instance.cursor().close()
+        return instance.__dict__['operators']
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    vendor = 'oracle'
+    display_name = 'Oracle'
+    # This dictionary maps Field objects to their associated Oracle column
+    # types, as strings. Column-type strings can contain format strings; they'll
+    # be interpolated against the values of Field.__dict__ before being output.
+    # If a column type is set to None, it won't be included in the output.
+    #
+    # Any format strings starting with "qn_" are quoted before being used in the
+    # output (the "qn_" prefix is stripped before the lookup is performed.
+    data_types = {
+        'AutoField': 'NUMBER(11) GENERATED BY DEFAULT ON NULL AS IDENTITY',
+        'BigAutoField': 'NUMBER(19) GENERATED BY DEFAULT ON NULL AS IDENTITY',
+        'BinaryField': 'BLOB',
+        'BooleanField': 'NUMBER(1)',
+        'CharField': 'NVARCHAR2(%(max_length)s)',
+        'DateField': 'DATE',
+        'DateTimeField': 'TIMESTAMP',
+        'DecimalField': 'NUMBER(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'INTERVAL DAY(9) TO SECOND(6)',
+        'FileField': 'NVARCHAR2(%(max_length)s)',
+        'FilePathField': 'NVARCHAR2(%(max_length)s)',
+        'FloatField': 'DOUBLE PRECISION',
+        'IntegerField': 'NUMBER(11)',
+        'BigIntegerField': 'NUMBER(19)',
+        'IPAddressField': 'VARCHAR2(15)',
+        'GenericIPAddressField': 'VARCHAR2(39)',
+        'NullBooleanField': 'NUMBER(1)',
+        'OneToOneField': 'NUMBER(11)',
+        'PositiveIntegerField': 'NUMBER(11)',
+        'PositiveSmallIntegerField': 'NUMBER(11)',
+        'SlugField': 'NVARCHAR2(%(max_length)s)',
+        'SmallAutoField': 'NUMBER(5) GENERATED BY DEFAULT ON NULL AS IDENTITY',
+        'SmallIntegerField': 'NUMBER(11)',
+        'TextField': 'NCLOB',
+        'TimeField': 'TIMESTAMP',
+        'URLField': 'VARCHAR2(%(max_length)s)',
+        'UUIDField': 'VARCHAR2(32)',
+    }
+    data_type_check_constraints = {
+        'BooleanField': '%(qn_column)s IN (0,1)',
+        'NullBooleanField': '%(qn_column)s IN (0,1)',
+        'PositiveIntegerField': '%(qn_column)s >= 0',
+        'PositiveSmallIntegerField': '%(qn_column)s >= 0',
+    }
+
+    # Oracle doesn't support a database index on these columns.
+    _limited_data_types = ('clob', 'nclob', 'blob')
+
+    operators = _UninitializedOperatorsDescriptor()
+
+    _standard_operators = {
+        'exact': '= %s',
+        'iexact': '= UPPER(%s)',
+        'contains': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+        'icontains': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+        'gt': '> %s',
+        'gte': '>= %s',
+        'lt': '< %s',
+        'lte': '<= %s',
+        'startswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+        'endswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+        'istartswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+        'iendswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
+    }
+
+    _likec_operators = {
+        **_standard_operators,
+        'contains': "LIKEC %s ESCAPE '\\'",
+        'icontains': "LIKEC UPPER(%s) ESCAPE '\\'",
+        'startswith': "LIKEC %s ESCAPE '\\'",
+        'endswith': "LIKEC %s ESCAPE '\\'",
+        'istartswith': "LIKEC UPPER(%s) ESCAPE '\\'",
+        'iendswith': "LIKEC UPPER(%s) ESCAPE '\\'",
+    }
+
+    # The patterns below are used to generate SQL pattern lookup clauses when
+    # the right-hand side of the lookup isn't a raw string (it might be an expression
+    # or the result of a bilateral transformation).
+    # In those cases, special characters for LIKE operators (e.g. \, %, _)
+    # should be escaped on the database side.
+    #
+    # Note: we use str.format() here for readability as '%' is used as a wildcard for
+    # the LIKE operator.
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
+    _pattern_ops = {
+        'contains': "'%%' || {} || '%%'",
+        'icontains': "'%%' || UPPER({}) || '%%'",
+        'startswith': "{} || '%%'",
+        'istartswith': "UPPER({}) || '%%'",
+        'endswith': "'%%' || {}",
+        'iendswith': "'%%' || UPPER({})",
+    }
+
+    _standard_pattern_ops = {k: "LIKE TRANSLATE( " + v + " USING NCHAR_CS)"
+                                " ESCAPE TRANSLATE('\\' USING NCHAR_CS)"
+                             for k, v in _pattern_ops.items()}
+    _likec_pattern_ops = {k: "LIKEC " + v + " ESCAPE '\\'"
+                          for k, v in _pattern_ops.items()}
+
+    Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+    validation_class = DatabaseValidation
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        use_returning_into = self.settings_dict["OPTIONS"].get('use_returning_into', True)
+        self.features.can_return_columns_from_insert = use_returning_into
+
+    def _dsn(self):
+        settings_dict = self.settings_dict
+        if not settings_dict['HOST'].strip():
+            settings_dict['HOST'] = 'localhost'
+        if settings_dict['PORT']:
+            return Database.makedsn(settings_dict['HOST'], int(settings_dict['PORT']), settings_dict['NAME'])
+        return settings_dict['NAME']
+
+    def _connect_string(self):
+        return '%s/"%s"@%s' % (self.settings_dict['USER'], self.settings_dict['PASSWORD'], self._dsn())
+
+    def get_connection_params(self):
+        conn_params = self.settings_dict['OPTIONS'].copy()
+        if 'use_returning_into' in conn_params:
+            del conn_params['use_returning_into']
+        return conn_params
+
+    @async_unsafe
+    def get_new_connection(self, conn_params):
+        return Database.connect(
+            user=self.settings_dict['USER'],
+            password=self.settings_dict['PASSWORD'],
+            dsn=self._dsn(),
+            **conn_params,
+        )
+
+    def init_connection_state(self):
+        cursor = self.create_cursor()
+        # Set the territory first. The territory overrides NLS_DATE_FORMAT
+        # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
+        # these are set in single statement it isn't clear what is supposed
+        # to happen.
+        cursor.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
+        # Set Oracle date to ANSI date format.  This only needs to execute
+        # once when we create a new connection. We also set the Territory
+        # to 'AMERICA' which forces Sunday to evaluate to a '1' in
+        # TO_CHAR().
+        cursor.execute(
+            "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
+            " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'" +
+            (" TIME_ZONE = 'UTC'" if settings.USE_TZ else '')
+        )
+        cursor.close()
+        if 'operators' not in self.__dict__:
+            # Ticket #14149: Check whether our LIKE implementation will
+            # work for this connection or we need to fall back on LIKEC.
+            # This check is performed only once per DatabaseWrapper
+            # instance per thread, since subsequent connections will use
+            # the same settings.
+            cursor = self.create_cursor()
+            try:
+                cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
+                               % self._standard_operators['contains'],
+                               ['X'])
+            except Database.DatabaseError:
+                self.operators = self._likec_operators
+                self.pattern_ops = self._likec_pattern_ops
+            else:
+                self.operators = self._standard_operators
+                self.pattern_ops = self._standard_pattern_ops
+            cursor.close()
+        self.connection.stmtcachesize = 20
+        # Ensure all changes are preserved even when AUTOCOMMIT is False.
+        if not self.get_autocommit():
+            self.commit()
+
+    @async_unsafe
+    def create_cursor(self, name=None):
+        return FormatStylePlaceholderCursor(self.connection)
+
+    def _commit(self):
+        if self.connection is not None:
+            with wrap_oracle_errors():
+                return self.connection.commit()
+
+    # Oracle doesn't support releasing savepoints. But we fake them when query
+    # logging is enabled to keep query counts consistent with other backends.
+    def _savepoint_commit(self, sid):
+        if self.queries_logged:
+            self.queries_log.append({
+                'sql': '-- RELEASE SAVEPOINT %s (faked)' % self.ops.quote_name(sid),
+                'time': '0.000',
+            })
+
+    def _set_autocommit(self, autocommit):
+        with self.wrap_database_errors:
+            self.connection.autocommit = autocommit
+
+    def check_constraints(self, table_names=None):
+        """
+        Check constraints by setting them to immediate. Return them to deferred
+        afterward.
+        """
+        self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
+        self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')
+
+    def is_usable(self):
+        try:
+            self.connection.ping()
+        except Database.Error:
+            return False
+        else:
+            return True
+
+    @cached_property
+    def oracle_version(self):
+        with self.temporary_connection():
+            return tuple(int(x) for x in self.connection.version.split('.'))
+
+
+class OracleParam:
+    """
+    Wrapper object for formatting parameters for Oracle. If the string
+    representation of the value is large enough (greater than 4000 characters)
+    the input size needs to be set as CLOB. Alternatively, if the parameter
+    has an `input_size` attribute, then the value of the `input_size` attribute
+    will be used instead. Otherwise, no input size will be set for the
+    parameter when executing the query.
+    """
+
+    def __init__(self, param, cursor, strings_only=False):
+        # With raw SQL queries, datetimes can reach this function
+        # without being converted by DateTimeField.get_db_prep_value.
+        if settings.USE_TZ and (isinstance(param, datetime.datetime) and
+                                not isinstance(param, Oracle_datetime)):
+            param = Oracle_datetime.from_datetime(param)
+
+        string_size = 0
+        # Oracle doesn't recognize True and False correctly.
+        if param is True:
+            param = 1
+        elif param is False:
+            param = 0
+        if hasattr(param, 'bind_parameter'):
+            self.force_bytes = param.bind_parameter(cursor)
+        elif isinstance(param, (Database.Binary, datetime.timedelta)):
+            self.force_bytes = param
+        else:
+            # To transmit to the database, we need Unicode if supported
+            # To get size right, we must consider bytes.
+            self.force_bytes = force_str(param, cursor.charset, strings_only)
+            if isinstance(self.force_bytes, str):
+                # We could optimize by only converting up to 4000 bytes here
+                string_size = len(force_bytes(param, cursor.charset, strings_only))
+        if hasattr(param, 'input_size'):
+            # If parameter has `input_size` attribute, use that.
+            self.input_size = param.input_size
+        elif string_size > 4000:
+            # Mark any string param greater than 4000 characters as a CLOB.
+            self.input_size = Database.CLOB
+        elif isinstance(param, datetime.datetime):
+            self.input_size = Database.TIMESTAMP
+        else:
+            self.input_size = None
+
+
+class VariableWrapper:
+    """
+    An adapter class for cursor variables that prevents the wrapped object
+    from being converted into a string when used to instantiate an OracleParam.
+    This can be used generally for any other object that should be passed into
+    Cursor.execute as-is.
+    """
+
+    def __init__(self, var):
+        self.var = var
+
+    def bind_parameter(self, cursor):
+        return self.var
+
+    def __getattr__(self, key):
+        return getattr(self.var, key)
+
+    def __setattr__(self, key, value):
+        if key == 'var':
+            self.__dict__[key] = value
+        else:
+            setattr(self.var, key, value)
+
+
+class FormatStylePlaceholderCursor:
+    """
+    Django uses "format" (e.g. '%s') style placeholders, but Oracle uses ":var"
+    style. This fixes it -- but note that if you want to use a literal "%s" in
+    a query, you'll need to use "%%s".
+    """
+    charset = 'utf-8'
+
+    def __init__(self, connection):
+        self.cursor = connection.cursor()
+        self.cursor.outputtypehandler = self._output_type_handler
+
+    @staticmethod
+    def _output_number_converter(value):
+        return decimal.Decimal(value) if '.' in value else int(value)
+
+    @staticmethod
+    def _get_decimal_converter(precision, scale):
+        if scale == 0:
+            return int
+        context = decimal.Context(prec=precision)
+        quantize_value = decimal.Decimal(1).scaleb(-scale)
+        return lambda v: decimal.Decimal(v).quantize(quantize_value, context=context)
+
+    @staticmethod
+    def _output_type_handler(cursor, name, defaultType, length, precision, scale):
+        """
+        Called for each db column fetched from cursors. Return numbers as the
+        appropriate Python type.
+        """
+        if defaultType == Database.NUMBER:
+            if scale == -127:
+                if precision == 0:
+                    # NUMBER column: decimal-precision floating point.
+                    # This will normally be an integer from a sequence,
+                    # but it could be a decimal value.
+                    outconverter = FormatStylePlaceholderCursor._output_number_converter
+                else:
+                    # FLOAT column: binary-precision floating point.
+                    # This comes from FloatField columns.
+                    outconverter = float
+            elif precision > 0:
+                # NUMBER(p,s) column: decimal-precision fixed point.
+                # This comes from IntegerField and DecimalField columns.
+                outconverter = FormatStylePlaceholderCursor._get_decimal_converter(precision, scale)
+            else:
+                # No type information. This normally comes from a
+                # mathematical expression in the SELECT list. Guess int
+                # or Decimal based on whether it has a decimal point.
+                outconverter = FormatStylePlaceholderCursor._output_number_converter
+            return cursor.var(
+                Database.STRING,
+                size=255,
+                arraysize=cursor.arraysize,
+                outconverter=outconverter,
+            )
+
+    def _format_params(self, params):
+        try:
+            return {k: OracleParam(v, self, True) for k, v in params.items()}
+        except AttributeError:
+            return tuple(OracleParam(p, self, True) for p in params)
+
+    def _guess_input_sizes(self, params_list):
+        # Try dict handling; if that fails, treat as sequence
+        if hasattr(params_list[0], 'keys'):
+            sizes = {}
+            for params in params_list:
+                for k, value in params.items():
+                    if value.input_size:
+                        sizes[k] = value.input_size
+            if sizes:
+                self.setinputsizes(**sizes)
+        else:
+            # It's not a list of dicts; it's a list of sequences
+            sizes = [None] * len(params_list[0])
+            for params in params_list:
+                for i, value in enumerate(params):
+                    if value.input_size:
+                        sizes[i] = value.input_size
+            if sizes:
+                self.setinputsizes(*sizes)
+
+    def _param_generator(self, params):
+        # Try dict handling; if that fails, treat as sequence
+        if hasattr(params, 'items'):
+            return {k: v.force_bytes for k, v in params.items()}
+        else:
+            return [p.force_bytes for p in params]
+
+    def _fix_for_params(self, query, params, unify_by_values=False):
+        # cx_Oracle wants no trailing ';' for SQL statements.  For PL/SQL, it
+        # it does want a trailing ';' but not a trailing '/'.  However, these
+        # characters must be included in the original query in case the query
+        # is being passed to SQL*Plus.
+        if query.endswith(';') or query.endswith('/'):
+            query = query[:-1]
+        if params is None:
+            params = []
+        elif hasattr(params, 'keys'):
+            # Handle params as dict
+            args = {k: ":%s" % k for k in params}
+            query = query % args
+        elif unify_by_values and params:
+            # Handle params as a dict with unified query parameters by their
+            # values. It can be used only in single query execute() because
+            # executemany() shares the formatted query with each of the params
+            # list. e.g. for input params = [0.75, 2, 0.75, 'sth', 0.75]
+            # params_dict = {0.75: ':arg0', 2: ':arg1', 'sth': ':arg2'}
+            # args = [':arg0', ':arg1', ':arg0', ':arg2', ':arg0']
+            # params = {':arg0': 0.75, ':arg1': 2, ':arg2': 'sth'}
+            params_dict = {
+                param: ':arg%d' % i
+                for i, param in enumerate(dict.fromkeys(params))
+            }
+            args = [params_dict[param] for param in params]
+            params = {value: key for key, value in params_dict.items()}
+            query = query % tuple(args)
+        else:
+            # Handle params as sequence
+            args = [(':arg%d' % i) for i in range(len(params))]
+            query = query % tuple(args)
+        return query, self._format_params(params)
+
+    def execute(self, query, params=None):
+        query, params = self._fix_for_params(query, params, unify_by_values=True)
+        self._guess_input_sizes([params])
+        with wrap_oracle_errors():
+            return self.cursor.execute(query, self._param_generator(params))
+
+    def executemany(self, query, params=None):
+        if not params:
+            # No params given, nothing to do
+            return None
+        # uniform treatment for sequences and iterables
+        params_iter = iter(params)
+        query, firstparams = self._fix_for_params(query, next(params_iter))
+        # we build a list of formatted params; as we're going to traverse it
+        # more than once, we can't make it lazy by using a generator
+        formatted = [firstparams] + [self._format_params(p) for p in params_iter]
+        self._guess_input_sizes(formatted)
+        with wrap_oracle_errors():
+            return self.cursor.executemany(query, [self._param_generator(p) for p in formatted])
+
+    def close(self):
+        try:
+            self.cursor.close()
+        except Database.InterfaceError:
+            # already closed
+            pass
+
+    def var(self, *args):
+        return VariableWrapper(self.cursor.var(*args))
+
+    def arrayvar(self, *args):
+        return VariableWrapper(self.cursor.arrayvar(*args))
+
+    def __getattr__(self, attr):
+        return getattr(self.cursor, attr)
+
+    def __iter__(self):
+        return iter(self.cursor)

venv/lib/python3.8/site-packages/django/db/backends/oracle/client.py

@@ -0,0 +1,17 @@
+import shutil
+import subprocess
+
+from django.db.backends.base.client import BaseDatabaseClient
+
+
+class DatabaseClient(BaseDatabaseClient):
+    executable_name = 'sqlplus'
+    wrapper_name = 'rlwrap'
+
+    def runshell(self):
+        conn_string = self.connection._connect_string()
+        args = [self.executable_name, "-L", conn_string]
+        wrapper_path = shutil.which(self.wrapper_name)
+        if wrapper_path:
+            args = [wrapper_path, *args]
+        subprocess.run(args, check=True)

venv/lib/python3.8/site-packages/django/db/backends/oracle/creation.py

@@ -0,0 +1,400 @@
+import sys
+
+from django.conf import settings
+from django.db.backends.base.creation import BaseDatabaseCreation
+from django.db.utils import DatabaseError
+from django.utils.crypto import get_random_string
+from django.utils.functional import cached_property
+
+TEST_DATABASE_PREFIX = 'test_'
+
+
+class DatabaseCreation(BaseDatabaseCreation):
+
+    @cached_property
+    def _maindb_connection(self):
+        """
+        This is analogous to other backends' `_nodb_connection` property,
+        which allows access to an "administrative" connection which can
+        be used to manage the test databases.
+        For Oracle, the only connection that can be used for that purpose
+        is the main (non-test) connection.
+        """
+        settings_dict = settings.DATABASES[self.connection.alias]
+        user = settings_dict.get('SAVED_USER') or settings_dict['USER']
+        password = settings_dict.get('SAVED_PASSWORD') or settings_dict['PASSWORD']
+        settings_dict = {**settings_dict, 'USER': user, 'PASSWORD': password}
+        DatabaseWrapper = type(self.connection)
+        return DatabaseWrapper(settings_dict, alias=self.connection.alias)
+
+    def _create_test_db(self, verbosity=1, autoclobber=False, keepdb=False):
+        parameters = self._get_test_db_params()
+        with self._maindb_connection.cursor() as cursor:
+            if self._test_database_create():
+                try:
+                    self._execute_test_db_creation(cursor, parameters, verbosity, keepdb)
+                except Exception as e:
+                    if 'ORA-01543' not in str(e):
+                        # All errors except "tablespace already exists" cancel tests
+                        self.log('Got an error creating the test database: %s' % e)
+                        sys.exit(2)
+                    if not autoclobber:
+                        confirm = input(
+                            "It appears the test database, %s, already exists. "
+                            "Type 'yes' to delete it, or 'no' to cancel: " % parameters['user'])
+                    if autoclobber or confirm == 'yes':
+                        if verbosity >= 1:
+                            self.log("Destroying old test database for alias '%s'..." % self.connection.alias)
+                        try:
+                            self._execute_test_db_destruction(cursor, parameters, verbosity)
+                        except DatabaseError as e:
+                            if 'ORA-29857' in str(e):
+                                self._handle_objects_preventing_db_destruction(cursor, parameters,
+                                                                               verbosity, autoclobber)
+                            else:
+                                # Ran into a database error that isn't about leftover objects in the tablespace
+                                self.log('Got an error destroying the old test database: %s' % e)
+                                sys.exit(2)
+                        except Exception as e:
+                            self.log('Got an error destroying the old test database: %s' % e)
+                            sys.exit(2)
+                        try:
+                            self._execute_test_db_creation(cursor, parameters, verbosity, keepdb)
+                        except Exception as e:
+                            self.log('Got an error recreating the test database: %s' % e)
+                            sys.exit(2)
+                    else:
+                        self.log('Tests cancelled.')
+                        sys.exit(1)
+
+            if self._test_user_create():
+                if verbosity >= 1:
+                    self.log('Creating test user...')
+                try:
+                    self._create_test_user(cursor, parameters, verbosity, keepdb)
+                except Exception as e:
+                    if 'ORA-01920' not in str(e):
+                        # All errors except "user already exists" cancel tests
+                        self.log('Got an error creating the test user: %s' % e)
+                        sys.exit(2)
+                    if not autoclobber:
+                        confirm = input(
+                            "It appears the test user, %s, already exists. Type "
+                            "'yes' to delete it, or 'no' to cancel: " % parameters['user'])
+                    if autoclobber or confirm == 'yes':
+                        try:
+                            if verbosity >= 1:
+                                self.log('Destroying old test user...')
+                            self._destroy_test_user(cursor, parameters, verbosity)
+                            if verbosity >= 1:
+                                self.log('Creating test user...')
+                            self._create_test_user(cursor, parameters, verbosity, keepdb)
+                        except Exception as e:
+                            self.log('Got an error recreating the test user: %s' % e)
+                            sys.exit(2)
+                    else:
+                        self.log('Tests cancelled.')
+                        sys.exit(1)
+        self._maindb_connection.close()  # done with main user -- test user and tablespaces created
+        self._switch_to_test_user(parameters)
+        return self.connection.settings_dict['NAME']
+
+    def _switch_to_test_user(self, parameters):
+        """
+        Switch to the user that's used for creating the test database.
+
+        Oracle doesn't have the concept of separate databases under the same
+        user, so a separate user is used; see _create_test_db(). The main user
+        is also needed for cleanup when testing is completed, so save its
+        credentials in the SAVED_USER/SAVED_PASSWORD key in the settings dict.
+        """
+        real_settings = settings.DATABASES[self.connection.alias]
+        real_settings['SAVED_USER'] = self.connection.settings_dict['SAVED_USER'] = \
+            self.connection.settings_dict['USER']
+        real_settings['SAVED_PASSWORD'] = self.connection.settings_dict['SAVED_PASSWORD'] = \
+            self.connection.settings_dict['PASSWORD']
+        real_test_settings = real_settings['TEST']
+        test_settings = self.connection.settings_dict['TEST']
+        real_test_settings['USER'] = real_settings['USER'] = test_settings['USER'] = \
+            self.connection.settings_dict['USER'] = parameters['user']
+        real_settings['PASSWORD'] = self.connection.settings_dict['PASSWORD'] = parameters['password']
+
+    def set_as_test_mirror(self, primary_settings_dict):
+        """
+        Set this database up to be used in testing as a mirror of a primary
+        database whose settings are given.
+        """
+        self.connection.settings_dict['USER'] = primary_settings_dict['USER']
+        self.connection.settings_dict['PASSWORD'] = primary_settings_dict['PASSWORD']
+
+    def _handle_objects_preventing_db_destruction(self, cursor, parameters, verbosity, autoclobber):
+        # There are objects in the test tablespace which prevent dropping it
+        # The easy fix is to drop the test user -- but are we allowed to do so?
+        self.log(
+            'There are objects in the old test database which prevent its destruction.\n'
+            'If they belong to the test user, deleting the user will allow the test '
+            'database to be recreated.\n'
+            'Otherwise, you will need to find and remove each of these objects, '
+            'or use a different tablespace.\n'
+        )
+        if self._test_user_create():
+            if not autoclobber:
+                confirm = input("Type 'yes' to delete user %s: " % parameters['user'])
+            if autoclobber or confirm == 'yes':
+                try:
+                    if verbosity >= 1:
+                        self.log('Destroying old test user...')
+                    self._destroy_test_user(cursor, parameters, verbosity)
+                except Exception as e:
+                    self.log('Got an error destroying the test user: %s' % e)
+                    sys.exit(2)
+                try:
+                    if verbosity >= 1:
+                        self.log("Destroying old test database for alias '%s'..." % self.connection.alias)
+                    self._execute_test_db_destruction(cursor, parameters, verbosity)
+                except Exception as e:
+                    self.log('Got an error destroying the test database: %s' % e)
+                    sys.exit(2)
+            else:
+                self.log('Tests cancelled -- test database cannot be recreated.')
+                sys.exit(1)
+        else:
+            self.log("Django is configured to use pre-existing test user '%s',"
+                     " and will not attempt to delete it." % parameters['user'])
+            self.log('Tests cancelled -- test database cannot be recreated.')
+            sys.exit(1)
+
+    def _destroy_test_db(self, test_database_name, verbosity=1):
+        """
+        Destroy a test database, prompting the user for confirmation if the
+        database already exists. Return the name of the test database created.
+        """
+        self.connection.settings_dict['USER'] = self.connection.settings_dict['SAVED_USER']
+        self.connection.settings_dict['PASSWORD'] = self.connection.settings_dict['SAVED_PASSWORD']
+        self.connection.close()
+        parameters = self._get_test_db_params()
+        with self._maindb_connection.cursor() as cursor:
+            if self._test_user_create():
+                if verbosity >= 1:
+                    self.log('Destroying test user...')
+                self._destroy_test_user(cursor, parameters, verbosity)
+            if self._test_database_create():
+                if verbosity >= 1:
+                    self.log('Destroying test database tables...')
+                self._execute_test_db_destruction(cursor, parameters, verbosity)
+        self._maindb_connection.close()
+
+    def _execute_test_db_creation(self, cursor, parameters, verbosity, keepdb=False):
+        if verbosity >= 2:
+            self.log('_create_test_db(): dbname = %s' % parameters['user'])
+        if self._test_database_oracle_managed_files():
+            statements = [
+                """
+                CREATE TABLESPACE %(tblspace)s
+                DATAFILE SIZE %(size)s
+                AUTOEXTEND ON NEXT %(extsize)s MAXSIZE %(maxsize)s
+                """,
+                """
+                CREATE TEMPORARY TABLESPACE %(tblspace_temp)s
+                TEMPFILE SIZE %(size_tmp)s
+                AUTOEXTEND ON NEXT %(extsize_tmp)s MAXSIZE %(maxsize_tmp)s
+                """,
+            ]
+        else:
+            statements = [
+                """
+                CREATE TABLESPACE %(tblspace)s
+                DATAFILE '%(datafile)s' SIZE %(size)s REUSE
+                AUTOEXTEND ON NEXT %(extsize)s MAXSIZE %(maxsize)s
+                """,
+                """
+                CREATE TEMPORARY TABLESPACE %(tblspace_temp)s
+                TEMPFILE '%(datafile_tmp)s' SIZE %(size_tmp)s REUSE
+                AUTOEXTEND ON NEXT %(extsize_tmp)s MAXSIZE %(maxsize_tmp)s
+                """,
+            ]
+        # Ignore "tablespace already exists" error when keepdb is on.
+        acceptable_ora_err = 'ORA-01543' if keepdb else None
+        self._execute_allow_fail_statements(cursor, statements, parameters, verbosity, acceptable_ora_err)
+
+    def _create_test_user(self, cursor, parameters, verbosity, keepdb=False):
+        if verbosity >= 2:
+            self.log('_create_test_user(): username = %s' % parameters['user'])
+        statements = [
+            """CREATE USER %(user)s
+               IDENTIFIED BY "%(password)s"
+               DEFAULT TABLESPACE %(tblspace)s
+               TEMPORARY TABLESPACE %(tblspace_temp)s
+               QUOTA UNLIMITED ON %(tblspace)s
+            """,
+            """GRANT CREATE SESSION,
+                     CREATE TABLE,
+                     CREATE SEQUENCE,
+                     CREATE PROCEDURE,
+                     CREATE TRIGGER
+               TO %(user)s""",
+        ]
+        # Ignore "user already exists" error when keepdb is on
+        acceptable_ora_err = 'ORA-01920' if keepdb else None
+        success = self._execute_allow_fail_statements(cursor, statements, parameters, verbosity, acceptable_ora_err)
+        # If the password was randomly generated, change the user accordingly.
+        if not success and self._test_settings_get('PASSWORD') is None:
+            set_password = 'ALTER USER %(user)s IDENTIFIED BY "%(password)s"'
+            self._execute_statements(cursor, [set_password], parameters, verbosity)
+        # Most test suites can be run without "create view" and
+        # "create materialized view" privileges. But some need it.
+        for object_type in ('VIEW', 'MATERIALIZED VIEW'):
+            extra = 'GRANT CREATE %(object_type)s TO %(user)s'
+            parameters['object_type'] = object_type
+            success = self._execute_allow_fail_statements(cursor, [extra], parameters, verbosity, 'ORA-01031')
+            if not success and verbosity >= 2:
+                self.log('Failed to grant CREATE %s permission to test user. This may be ok.' % object_type)
+
+    def _execute_test_db_destruction(self, cursor, parameters, verbosity):
+        if verbosity >= 2:
+            self.log('_execute_test_db_destruction(): dbname=%s' % parameters['user'])
+        statements = [
+            'DROP TABLESPACE %(tblspace)s INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS',
+            'DROP TABLESPACE %(tblspace_temp)s INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS',
+        ]
+        self._execute_statements(cursor, statements, parameters, verbosity)
+
+    def _destroy_test_user(self, cursor, parameters, verbosity):
+        if verbosity >= 2:
+            self.log('_destroy_test_user(): user=%s' % parameters['user'])
+            self.log('Be patient. This can take some time...')
+        statements = [
+            'DROP USER %(user)s CASCADE',
+        ]
+        self._execute_statements(cursor, statements, parameters, verbosity)
+
+    def _execute_statements(self, cursor, statements, parameters, verbosity, allow_quiet_fail=False):
+        for template in statements:
+            stmt = template % parameters
+            if verbosity >= 2:
+                print(stmt)
+            try:
+                cursor.execute(stmt)
+            except Exception as err:
+                if (not allow_quiet_fail) or verbosity >= 2:
+                    self.log('Failed (%s)' % (err))
+                raise
+
+    def _execute_allow_fail_statements(self, cursor, statements, parameters, verbosity, acceptable_ora_err):
+        """
+        Execute statements which are allowed to fail silently if the Oracle
+        error code given by `acceptable_ora_err` is raised. Return True if the
+        statements execute without an exception, or False otherwise.
+        """
+        try:
+            # Statement can fail when acceptable_ora_err is not None
+            allow_quiet_fail = acceptable_ora_err is not None and len(acceptable_ora_err) > 0
+            self._execute_statements(cursor, statements, parameters, verbosity, allow_quiet_fail=allow_quiet_fail)
+            return True
+        except DatabaseError as err:
+            description = str(err)
+            if acceptable_ora_err is None or acceptable_ora_err not in description:
+                raise
+            return False
+
+    def _get_test_db_params(self):
+        return {
+            'dbname': self._test_database_name(),
+            'user': self._test_database_user(),
+            'password': self._test_database_passwd(),
+            'tblspace': self._test_database_tblspace(),
+            'tblspace_temp': self._test_database_tblspace_tmp(),
+            'datafile': self._test_database_tblspace_datafile(),
+            'datafile_tmp': self._test_database_tblspace_tmp_datafile(),
+            'maxsize': self._test_database_tblspace_maxsize(),
+            'maxsize_tmp': self._test_database_tblspace_tmp_maxsize(),
+            'size': self._test_database_tblspace_size(),
+            'size_tmp': self._test_database_tblspace_tmp_size(),
+            'extsize': self._test_database_tblspace_extsize(),
+            'extsize_tmp': self._test_database_tblspace_tmp_extsize(),
+        }
+
+    def _test_settings_get(self, key, default=None, prefixed=None):
+        """
+        Return a value from the test settings dict, or a given default, or a
+        prefixed entry from the main settings dict.
+        """
+        settings_dict = self.connection.settings_dict
+        val = settings_dict['TEST'].get(key, default)
+        if val is None and prefixed:
+            val = TEST_DATABASE_PREFIX + settings_dict[prefixed]
+        return val
+
+    def _test_database_name(self):
+        return self._test_settings_get('NAME', prefixed='NAME')
+
+    def _test_database_create(self):
+        return self._test_settings_get('CREATE_DB', default=True)
+
+    def _test_user_create(self):
+        return self._test_settings_get('CREATE_USER', default=True)
+
+    def _test_database_user(self):
+        return self._test_settings_get('USER', prefixed='USER')
+
+    def _test_database_passwd(self):
+        password = self._test_settings_get('PASSWORD')
+        if password is None and self._test_user_create():
+            # Oracle passwords are limited to 30 chars and can't contain symbols.
+            password = get_random_string(length=30)
+        return password
+
+    def _test_database_tblspace(self):
+        return self._test_settings_get('TBLSPACE', prefixed='USER')
+
+    def _test_database_tblspace_tmp(self):
+        settings_dict = self.connection.settings_dict
+        return settings_dict['TEST'].get('TBLSPACE_TMP',
+                                         TEST_DATABASE_PREFIX + settings_dict['USER'] + '_temp')
+
+    def _test_database_tblspace_datafile(self):
+        tblspace = '%s.dbf' % self._test_database_tblspace()
+        return self._test_settings_get('DATAFILE', default=tblspace)
+
+    def _test_database_tblspace_tmp_datafile(self):
+        tblspace = '%s.dbf' % self._test_database_tblspace_tmp()
+        return self._test_settings_get('DATAFILE_TMP', default=tblspace)
+
+    def _test_database_tblspace_maxsize(self):
+        return self._test_settings_get('DATAFILE_MAXSIZE', default='500M')
+
+    def _test_database_tblspace_tmp_maxsize(self):
+        return self._test_settings_get('DATAFILE_TMP_MAXSIZE', default='500M')
+
+    def _test_database_tblspace_size(self):
+        return self._test_settings_get('DATAFILE_SIZE', default='50M')
+
+    def _test_database_tblspace_tmp_size(self):
+        return self._test_settings_get('DATAFILE_TMP_SIZE', default='50M')
+
+    def _test_database_tblspace_extsize(self):
+        return self._test_settings_get('DATAFILE_EXTSIZE', default='25M')
+
+    def _test_database_tblspace_tmp_extsize(self):
+        return self._test_settings_get('DATAFILE_TMP_EXTSIZE', default='25M')
+
+    def _test_database_oracle_managed_files(self):
+        return self._test_settings_get('ORACLE_MANAGED_FILES', default=False)
+
+    def _get_test_db_name(self):
+        """
+        Return the 'production' DB name to get the test DB creation machinery
+        to work. This isn't a great deal in this case because DB names as
+        handled by Django don't have real counterparts in Oracle.
+        """
+        return self.connection.settings_dict['NAME']
+
+    def test_db_signature(self):
+        settings_dict = self.connection.settings_dict
+        return (
+            settings_dict['HOST'],
+            settings_dict['PORT'],
+            settings_dict['ENGINE'],
+            settings_dict['NAME'],
+            self._test_database_user(),
+        )

venv/lib/python3.8/site-packages/django/db/backends/oracle/features.py

@@ -0,0 +1,61 @@
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.utils import InterfaceError
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    interprets_empty_strings_as_nulls = True
+    has_select_for_update = True
+    has_select_for_update_nowait = True
+    has_select_for_update_skip_locked = True
+    has_select_for_update_of = True
+    select_for_update_of_column = True
+    can_return_columns_from_insert = True
+    can_introspect_autofield = True
+    supports_subqueries_in_group_by = False
+    supports_transactions = True
+    supports_timezones = False
+    has_native_duration_field = True
+    can_defer_constraint_checks = True
+    supports_partially_nullable_unique_constraints = False
+    truncates_names = True
+    supports_tablespaces = True
+    supports_sequence_reset = False
+    can_introspect_materialized_views = True
+    can_introspect_time_field = False
+    atomic_transactions = False
+    supports_combined_alters = False
+    nulls_order_largest = True
+    requires_literal_defaults = True
+    closed_cursor_error_class = InterfaceError
+    bare_select_suffix = " FROM DUAL"
+    # select for update with limit can be achieved on Oracle, but not with the current backend.
+    supports_select_for_update_with_limit = False
+    supports_temporal_subtraction = True
+    # Oracle doesn't ignore quoted identifiers case but the current backend
+    # does by uppercasing all identifiers.
+    ignores_table_name_case = True
+    supports_index_on_text_field = False
+    has_case_insensitive_like = False
+    create_test_procedure_without_params_sql = """
+        CREATE PROCEDURE "TEST_PROCEDURE" AS
+            V_I INTEGER;
+        BEGIN
+            V_I := 1;
+        END;
+    """
+    create_test_procedure_with_int_param_sql = """
+        CREATE PROCEDURE "TEST_PROCEDURE" (P_I INTEGER) AS
+            V_I INTEGER;
+        BEGIN
+            V_I := P_I;
+        END;
+    """
+    supports_callproc_kwargs = True
+    supports_over_clause = True
+    supports_frame_range_fixed_distance = True
+    supports_ignore_conflicts = False
+    max_query_params = 2**16 - 1
+    supports_partial_indexes = False
+    supports_slicing_ordering_in_compound = True
+    allows_multiple_constraints_on_same_fields = False
+    supports_boolean_expr_in_select_clause = False

venv/lib/python3.8/site-packages/django/db/backends/oracle/functions.py

@@ -0,0 +1,22 @@
+from django.db.models import DecimalField, DurationField, Func
+
+
+class IntervalToSeconds(Func):
+    function = ''
+    template = """
+    EXTRACT(day from %(expressions)s) * 86400 +
+    EXTRACT(hour from %(expressions)s) * 3600 +
+    EXTRACT(minute from %(expressions)s) * 60 +
+    EXTRACT(second from %(expressions)s)
+    """
+
+    def __init__(self, expression, *, output_field=None, **extra):
+        super().__init__(expression, output_field=output_field or DecimalField(), **extra)
+
+
+class SecondsToInterval(Func):
+    function = 'NUMTODSINTERVAL'
+    template = "%(function)s(%(expressions)s, 'SECOND')"
+
+    def __init__(self, expression, *, output_field=None, **extra):
+        super().__init__(expression, output_field=output_field or DurationField(), **extra)

venv/lib/python3.8/site-packages/django/db/backends/oracle/introspection.py

@@ -0,0 +1,294 @@
+from collections import namedtuple
+
+import cx_Oracle
+
+from django.db import models
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo as BaseFieldInfo, TableInfo,
+)
+
+FieldInfo = namedtuple('FieldInfo', BaseFieldInfo._fields + ('is_autofield',))
+
+
+class DatabaseIntrospection(BaseDatabaseIntrospection):
+    # Maps type objects to Django Field types.
+    data_types_reverse = {
+        cx_Oracle.BLOB: 'BinaryField',
+        cx_Oracle.CLOB: 'TextField',
+        cx_Oracle.DATETIME: 'DateField',
+        cx_Oracle.FIXED_CHAR: 'CharField',
+        cx_Oracle.FIXED_NCHAR: 'CharField',
+        cx_Oracle.INTERVAL: 'DurationField',
+        cx_Oracle.NATIVE_FLOAT: 'FloatField',
+        cx_Oracle.NCHAR: 'CharField',
+        cx_Oracle.NCLOB: 'TextField',
+        cx_Oracle.NUMBER: 'DecimalField',
+        cx_Oracle.STRING: 'CharField',
+        cx_Oracle.TIMESTAMP: 'DateTimeField',
+    }
+
+    cache_bust_counter = 1
+
+    def get_field_type(self, data_type, description):
+        if data_type == cx_Oracle.NUMBER:
+            precision, scale = description[4:6]
+            if scale == 0:
+                if precision > 11:
+                    return 'BigAutoField' if description.is_autofield else 'BigIntegerField'
+                elif 1 < precision < 6 and description.is_autofield:
+                    return 'SmallAutoField'
+                elif precision == 1:
+                    return 'BooleanField'
+                elif description.is_autofield:
+                    return 'AutoField'
+                else:
+                    return 'IntegerField'
+            elif scale == -127:
+                return 'FloatField'
+
+        return super().get_field_type(data_type, description)
+
+    def get_table_list(self, cursor):
+        """Return a list of table and view names in the current database."""
+        cursor.execute("""
+            SELECT table_name, 't'
+            FROM user_tables
+            WHERE
+                NOT EXISTS (
+                    SELECT 1
+                    FROM user_mviews
+                    WHERE user_mviews.mview_name = user_tables.table_name
+                )
+            UNION ALL
+            SELECT view_name, 'v' FROM user_views
+            UNION ALL
+            SELECT mview_name, 'v' FROM user_mviews
+        """)
+        return [TableInfo(self.identifier_converter(row[0]), row[1]) for row in cursor.fetchall()]
+
+    def get_table_description(self, cursor, table_name):
+        """
+        Return a description of the table with the DB-API cursor.description
+        interface.
+        """
+        # user_tab_columns gives data default for columns
+        cursor.execute("""
+            SELECT
+                column_name,
+                data_default,
+                CASE
+                    WHEN char_used IS NULL THEN data_length
+                    ELSE char_length
+                END as internal_size,
+                CASE
+                    WHEN identity_column = 'YES' THEN 1
+                    ELSE 0
+                END as is_autofield
+            FROM user_tab_cols
+            WHERE table_name = UPPER(%s)""", [table_name])
+        field_map = {
+            column: (internal_size, default if default != 'NULL' else None, is_autofield)
+            for column, default, internal_size, is_autofield in cursor.fetchall()
+        }
+        self.cache_bust_counter += 1
+        cursor.execute("SELECT * FROM {} WHERE ROWNUM < 2 AND {} > 0".format(
+            self.connection.ops.quote_name(table_name),
+            self.cache_bust_counter))
+        description = []
+        for desc in cursor.description:
+            name = desc[0]
+            internal_size, default, is_autofield = field_map[name]
+            name = name % {}  # cx_Oracle, for some reason, doubles percent signs.
+            description.append(FieldInfo(
+                self.identifier_converter(name), *desc[1:3], internal_size, desc[4] or 0,
+                desc[5] or 0, *desc[6:], default, is_autofield,
+            ))
+        return description
+
+    def identifier_converter(self, name):
+        """Identifier comparison is case insensitive under Oracle."""
+        return name.lower()
+
+    def get_sequences(self, cursor, table_name, table_fields=()):
+        cursor.execute("""
+            SELECT
+                user_tab_identity_cols.sequence_name,
+                user_tab_identity_cols.column_name
+            FROM
+                user_tab_identity_cols,
+                user_constraints,
+                user_cons_columns cols
+            WHERE
+                user_constraints.constraint_name = cols.constraint_name
+                AND user_constraints.table_name = user_tab_identity_cols.table_name
+                AND cols.column_name = user_tab_identity_cols.column_name
+                AND user_constraints.constraint_type = 'P'
+                AND user_tab_identity_cols.table_name = UPPER(%s)
+        """, [table_name])
+        # Oracle allows only one identity column per table.
+        row = cursor.fetchone()
+        if row:
+            return [{
+                'name': self.identifier_converter(row[0]),
+                'table': self.identifier_converter(table_name),
+                'column': self.identifier_converter(row[1]),
+            }]
+        # To keep backward compatibility for AutoFields that aren't Oracle
+        # identity columns.
+        for f in table_fields:
+            if isinstance(f, models.AutoField):
+                return [{'table': table_name, 'column': f.column}]
+        return []
+
+    def get_relations(self, cursor, table_name):
+        """
+        Return a dictionary of {field_name: (field_name_other_table, other_table)}
+        representing all relationships to the given table.
+        """
+        table_name = table_name.upper()
+        cursor.execute("""
+    SELECT ca.column_name, cb.table_name, cb.column_name
+    FROM   user_constraints, USER_CONS_COLUMNS ca, USER_CONS_COLUMNS cb
+    WHERE  user_constraints.table_name = %s AND
+           user_constraints.constraint_name = ca.constraint_name AND
+           user_constraints.r_constraint_name = cb.constraint_name AND
+           ca.position = cb.position""", [table_name])
+
+        return {
+            self.identifier_converter(field_name): (
+                self.identifier_converter(rel_field_name),
+                self.identifier_converter(rel_table_name),
+            ) for field_name, rel_table_name, rel_field_name in cursor.fetchall()
+        }
+
+    def get_key_columns(self, cursor, table_name):
+        cursor.execute("""
+            SELECT ccol.column_name, rcol.table_name AS referenced_table, rcol.column_name AS referenced_column
+            FROM user_constraints c
+            JOIN user_cons_columns ccol
+              ON ccol.constraint_name = c.constraint_name
+            JOIN user_cons_columns rcol
+              ON rcol.constraint_name = c.r_constraint_name
+            WHERE c.table_name = %s AND c.constraint_type = 'R'""", [table_name.upper()])
+        return [
+            tuple(self.identifier_converter(cell) for cell in row)
+            for row in cursor.fetchall()
+        ]
+
+    def get_primary_key_column(self, cursor, table_name):
+        cursor.execute("""
+            SELECT
+                cols.column_name
+            FROM
+                user_constraints,
+                user_cons_columns cols
+            WHERE
+                user_constraints.constraint_name = cols.constraint_name AND
+                user_constraints.constraint_type = 'P' AND
+                user_constraints.table_name = UPPER(%s) AND
+                cols.position = 1
+        """, [table_name])
+        row = cursor.fetchone()
+        return self.identifier_converter(row[0]) if row else None
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieve any constraints or keys (unique, pk, fk, check, index) across
+        one or more columns.
+        """
+        constraints = {}
+        # Loop over the constraints, getting PKs, uniques, and checks
+        cursor.execute("""
+            SELECT
+                user_constraints.constraint_name,
+                LISTAGG(LOWER(cols.column_name), ',') WITHIN GROUP (ORDER BY cols.position),
+                CASE user_constraints.constraint_type
+                    WHEN 'P' THEN 1
+                    ELSE 0
+                END AS is_primary_key,
+                CASE
+                    WHEN user_constraints.constraint_type IN ('P', 'U') THEN 1
+                    ELSE 0
+                END AS is_unique,
+                CASE user_constraints.constraint_type
+                    WHEN 'C' THEN 1
+                    ELSE 0
+                END AS is_check_constraint
+            FROM
+                user_constraints
+            LEFT OUTER JOIN
+                user_cons_columns cols ON user_constraints.constraint_name = cols.constraint_name
+            WHERE
+                user_constraints.constraint_type = ANY('P', 'U', 'C')
+                AND user_constraints.table_name = UPPER(%s)
+            GROUP BY user_constraints.constraint_name, user_constraints.constraint_type
+        """, [table_name])
+        for constraint, columns, pk, unique, check in cursor.fetchall():
+            constraint = self.identifier_converter(constraint)
+            constraints[constraint] = {
+                'columns': columns.split(','),
+                'primary_key': pk,
+                'unique': unique,
+                'foreign_key': None,
+                'check': check,
+                'index': unique,  # All uniques come with an index
+            }
+        # Foreign key constraints
+        cursor.execute("""
+            SELECT
+                cons.constraint_name,
+                LISTAGG(LOWER(cols.column_name), ',') WITHIN GROUP (ORDER BY cols.position),
+                LOWER(rcols.table_name),
+                LOWER(rcols.column_name)
+            FROM
+                user_constraints cons
+            INNER JOIN
+                user_cons_columns rcols ON rcols.constraint_name = cons.r_constraint_name AND rcols.position = 1
+            LEFT OUTER JOIN
+                user_cons_columns cols ON cons.constraint_name = cols.constraint_name
+            WHERE
+                cons.constraint_type = 'R' AND
+                cons.table_name = UPPER(%s)
+            GROUP BY cons.constraint_name, rcols.table_name, rcols.column_name
+        """, [table_name])
+        for constraint, columns, other_table, other_column in cursor.fetchall():
+            constraint = self.identifier_converter(constraint)
+            constraints[constraint] = {
+                'primary_key': False,
+                'unique': False,
+                'foreign_key': (other_table, other_column),
+                'check': False,
+                'index': False,
+                'columns': columns.split(','),
+            }
+        # Now get indexes
+        cursor.execute("""
+            SELECT
+                ind.index_name,
+                LOWER(ind.index_type),
+                LISTAGG(LOWER(cols.column_name), ',') WITHIN GROUP (ORDER BY cols.column_position),
+                LISTAGG(cols.descend, ',') WITHIN GROUP (ORDER BY cols.column_position)
+            FROM
+                user_ind_columns cols, user_indexes ind
+            WHERE
+                cols.table_name = UPPER(%s) AND
+                NOT EXISTS (
+                    SELECT 1
+                    FROM user_constraints cons
+                    WHERE ind.index_name = cons.index_name
+                ) AND cols.index_name = ind.index_name
+            GROUP BY ind.index_name, ind.index_type
+        """, [table_name])
+        for constraint, type_, columns, orders in cursor.fetchall():
+            constraint = self.identifier_converter(constraint)
+            constraints[constraint] = {
+                'primary_key': False,
+                'unique': False,
+                'foreign_key': None,
+                'check': False,
+                'index': True,
+                'type': 'idx' if type_ == 'normal' else type_,
+                'columns': columns.split(','),
+                'orders': orders.split(','),
+            }
+        return constraints

venv/lib/python3.8/site-packages/django/db/backends/oracle/operations.py

@@ -0,0 +1,631 @@
+import datetime
+import re
+import uuid
+from functools import lru_cache
+
+from django.conf import settings
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.backends.utils import strip_quotes, truncate_name
+from django.db.models.expressions import Exists, ExpressionWrapper, RawSQL
+from django.db.models.query_utils import Q
+from django.db.utils import DatabaseError
+from django.utils import timezone
+from django.utils.encoding import force_bytes, force_str
+from django.utils.functional import cached_property
+
+from .base import Database
+from .utils import BulkInsertMapper, InsertVar, Oracle_datetime
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    # Oracle uses NUMBER(5), NUMBER(11), and NUMBER(19) for integer fields.
+    # SmallIntegerField uses NUMBER(11) instead of NUMBER(5), which is used by
+    # SmallAutoField, to preserve backward compatibility.
+    integer_field_ranges = {
+        'SmallIntegerField': (-99999999999, 99999999999),
+        'IntegerField': (-99999999999, 99999999999),
+        'BigIntegerField': (-9999999999999999999, 9999999999999999999),
+        'PositiveSmallIntegerField': (0, 99999999999),
+        'PositiveIntegerField': (0, 99999999999),
+        'SmallAutoField': (-99999, 99999),
+        'AutoField': (-99999999999, 99999999999),
+        'BigAutoField': (-9999999999999999999, 9999999999999999999),
+    }
+    set_operators = {**BaseDatabaseOperations.set_operators, 'difference': 'MINUS'}
+
+    # TODO: colorize this SQL code with style.SQL_KEYWORD(), etc.
+    _sequence_reset_sql = """
+DECLARE
+    table_value integer;
+    seq_value integer;
+    seq_name user_tab_identity_cols.sequence_name%%TYPE;
+BEGIN
+    BEGIN
+        SELECT sequence_name INTO seq_name FROM user_tab_identity_cols
+        WHERE  table_name = '%(table_name)s' AND
+               column_name = '%(column_name)s';
+        EXCEPTION WHEN NO_DATA_FOUND THEN
+            seq_name := '%(no_autofield_sequence_name)s';
+    END;
+
+    SELECT NVL(MAX(%(column)s), 0) INTO table_value FROM %(table)s;
+    SELECT NVL(last_number - cache_size, 0) INTO seq_value FROM user_sequences
+           WHERE sequence_name = seq_name;
+    WHILE table_value > seq_value LOOP
+        EXECUTE IMMEDIATE 'SELECT "'||seq_name||'".nextval FROM DUAL'
+        INTO seq_value;
+    END LOOP;
+END;
+/"""
+
+    # Oracle doesn't support string without precision; use the max string size.
+    cast_char_field_without_max_length = 'NVARCHAR2(2000)'
+    cast_data_types = {
+        'AutoField': 'NUMBER(11)',
+        'BigAutoField': 'NUMBER(19)',
+        'SmallAutoField': 'NUMBER(5)',
+        'TextField': cast_char_field_without_max_length,
+    }
+
+    def cache_key_culling_sql(self):
+        return 'SELECT cache_key FROM %s ORDER BY cache_key OFFSET %%s ROWS FETCH FIRST 1 ROWS ONLY'
+
+    def date_extract_sql(self, lookup_type, field_name):
+        if lookup_type == 'week_day':
+            # TO_CHAR(field, 'D') returns an integer from 1-7, where 1=Sunday.
+            return "TO_CHAR(%s, 'D')" % field_name
+        elif lookup_type == 'week':
+            # IW = ISO week number
+            return "TO_CHAR(%s, 'IW')" % field_name
+        elif lookup_type == 'quarter':
+            return "TO_CHAR(%s, 'Q')" % field_name
+        elif lookup_type == 'iso_year':
+            return "TO_CHAR(%s, 'IYYY')" % field_name
+        else:
+            # https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/EXTRACT-datetime.html
+            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        # https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/ROUND-and-TRUNC-Date-Functions.html
+        if lookup_type in ('year', 'month'):
+            return "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
+        elif lookup_type == 'quarter':
+            return "TRUNC(%s, 'Q')" % field_name
+        elif lookup_type == 'week':
+            return "TRUNC(%s, 'IW')" % field_name
+        else:
+            return "TRUNC(%s)" % field_name
+
+    # Oracle crashes with "ORA-03113: end-of-file on communication channel"
+    # if the time zone name is passed in parameter. Use interpolation instead.
+    # https://groups.google.com/forum/#!msg/django-developers/zwQju7hbG78/9l934yelwfsJ
+    # This regexp matches all time zone names from the zoneinfo database.
+    _tzname_re = re.compile(r'^[\w/:+-]+$')
+
+    def _prepare_tzname_delta(self, tzname):
+        if '+' in tzname:
+            return tzname[tzname.find('+'):]
+        elif '-' in tzname:
+            return tzname[tzname.find('-'):]
+        return tzname
+
+    def _convert_field_to_tz(self, field_name, tzname):
+        if not settings.USE_TZ:
+            return field_name
+        if not self._tzname_re.match(tzname):
+            raise ValueError("Invalid time zone name: %s" % tzname)
+        # Convert from connection timezone to the local time, returning
+        # TIMESTAMP WITH TIME ZONE and cast it back to TIMESTAMP to strip the
+        # TIME ZONE details.
+        if self.connection.timezone_name != tzname:
+            return "CAST((FROM_TZ(%s, '%s') AT TIME ZONE '%s') AS TIMESTAMP)" % (
+                field_name,
+                self.connection.timezone_name,
+                self._prepare_tzname_delta(tzname),
+            )
+        return field_name
+
+    def datetime_cast_date_sql(self, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return 'TRUNC(%s)' % field_name
+
+    def datetime_cast_time_sql(self, field_name, tzname):
+        # Since `TimeField` values are stored as TIMESTAMP where only the date
+        # part is ignored, convert the field to the specified timezone.
+        return self._convert_field_to_tz(field_name, tzname)
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return self.date_extract_sql(lookup_type, field_name)
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        # https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/ROUND-and-TRUNC-Date-Functions.html
+        if lookup_type in ('year', 'month'):
+            sql = "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
+        elif lookup_type == 'quarter':
+            sql = "TRUNC(%s, 'Q')" % field_name
+        elif lookup_type == 'week':
+            sql = "TRUNC(%s, 'IW')" % field_name
+        elif lookup_type == 'day':
+            sql = "TRUNC(%s)" % field_name
+        elif lookup_type == 'hour':
+            sql = "TRUNC(%s, 'HH24')" % field_name
+        elif lookup_type == 'minute':
+            sql = "TRUNC(%s, 'MI')" % field_name
+        else:
+            sql = "CAST(%s AS DATE)" % field_name  # Cast to DATE removes sub-second precision.
+        return sql
+
+    def time_trunc_sql(self, lookup_type, field_name):
+        # The implementation is similar to `datetime_trunc_sql` as both
+        # `DateTimeField` and `TimeField` are stored as TIMESTAMP where
+        # the date part of the later is ignored.
+        if lookup_type == 'hour':
+            sql = "TRUNC(%s, 'HH24')" % field_name
+        elif lookup_type == 'minute':
+            sql = "TRUNC(%s, 'MI')" % field_name
+        elif lookup_type == 'second':
+            sql = "CAST(%s AS DATE)" % field_name  # Cast to DATE removes sub-second precision.
+        return sql
+
+    def get_db_converters(self, expression):
+        converters = super().get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type == 'TextField':
+            converters.append(self.convert_textfield_value)
+        elif internal_type == 'BinaryField':
+            converters.append(self.convert_binaryfield_value)
+        elif internal_type in ['BooleanField', 'NullBooleanField']:
+            converters.append(self.convert_booleanfield_value)
+        elif internal_type == 'DateTimeField':
+            if settings.USE_TZ:
+                converters.append(self.convert_datetimefield_value)
+        elif internal_type == 'DateField':
+            converters.append(self.convert_datefield_value)
+        elif internal_type == 'TimeField':
+            converters.append(self.convert_timefield_value)
+        elif internal_type == 'UUIDField':
+            converters.append(self.convert_uuidfield_value)
+        # Oracle stores empty strings as null. If the field accepts the empty
+        # string, undo this to adhere to the Django convention of using
+        # the empty string instead of null.
+        if expression.field.empty_strings_allowed:
+            converters.append(
+                self.convert_empty_bytes
+                if internal_type == 'BinaryField' else
+                self.convert_empty_string
+            )
+        return converters
+
+    def convert_textfield_value(self, value, expression, connection):
+        if isinstance(value, Database.LOB):
+            value = value.read()
+        return value
+
+    def convert_binaryfield_value(self, value, expression, connection):
+        if isinstance(value, Database.LOB):
+            value = force_bytes(value.read())
+        return value
+
+    def convert_booleanfield_value(self, value, expression, connection):
+        if value in (0, 1):
+            value = bool(value)
+        return value
+
+    # cx_Oracle always returns datetime.datetime objects for
+    # DATE and TIMESTAMP columns, but Django wants to see a
+    # python datetime.date, .time, or .datetime.
+
+    def convert_datetimefield_value(self, value, expression, connection):
+        if value is not None:
+            value = timezone.make_aware(value, self.connection.timezone)
+        return value
+
+    def convert_datefield_value(self, value, expression, connection):
+        if isinstance(value, Database.Timestamp):
+            value = value.date()
+        return value
+
+    def convert_timefield_value(self, value, expression, connection):
+        if isinstance(value, Database.Timestamp):
+            value = value.time()
+        return value
+
+    def convert_uuidfield_value(self, value, expression, connection):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    @staticmethod
+    def convert_empty_string(value, expression, connection):
+        return '' if value is None else value
+
+    @staticmethod
+    def convert_empty_bytes(value, expression, connection):
+        return b'' if value is None else value
+
+    def deferrable_sql(self):
+        return " DEFERRABLE INITIALLY DEFERRED"
+
+    def fetch_returned_insert_columns(self, cursor):
+        value = cursor._insert_id_var.getvalue()
+        if value is None or value == []:
+            # cx_Oracle < 6.3 returns None, >= 6.3 returns empty list.
+            raise DatabaseError(
+                'The database did not return a new row id. Probably "ORA-1403: '
+                'no data found" was raised internally but was hidden by the '
+                'Oracle OCI library (see https://code.djangoproject.com/ticket/28859).'
+            )
+        # cx_Oracle < 7 returns value, >= 7 returns list with single value.
+        return value if isinstance(value, list) else [value]
+
+    def field_cast_sql(self, db_type, internal_type):
+        if db_type and db_type.endswith('LOB'):
+            return "DBMS_LOB.SUBSTR(%s)"
+        else:
+            return "%s"
+
+    def no_limit_value(self):
+        return None
+
+    def limit_offset_sql(self, low_mark, high_mark):
+        fetch, offset = self._get_limit_offset_params(low_mark, high_mark)
+        return ' '.join(sql for sql in (
+            ('OFFSET %d ROWS' % offset) if offset else None,
+            ('FETCH FIRST %d ROWS ONLY' % fetch) if fetch else None,
+        ) if sql)
+
+    def last_executed_query(self, cursor, sql, params):
+        # https://cx-oracle.readthedocs.io/en/latest/cursor.html#Cursor.statement
+        # The DB API definition does not define this attribute.
+        statement = cursor.statement
+        # Unlike Psycopg's `query` and MySQLdb`'s `_executed`, cx_Oracle's
+        # `statement` doesn't contain the query parameters. Substitute
+        # parameters manually.
+        if isinstance(params, (tuple, list)):
+            for i, param in enumerate(params):
+                statement = statement.replace(':arg%d' % i, force_str(param, errors='replace'))
+        elif isinstance(params, dict):
+            for key, param in params.items():
+                statement = statement.replace(':%s' % key, force_str(param, errors='replace'))
+        return statement
+
+    def last_insert_id(self, cursor, table_name, pk_name):
+        sq_name = self._get_sequence_name(cursor, strip_quotes(table_name), pk_name)
+        cursor.execute('"%s".currval' % sq_name)
+        return cursor.fetchone()[0]
+
+    def lookup_cast(self, lookup_type, internal_type=None):
+        if lookup_type in ('iexact', 'icontains', 'istartswith', 'iendswith'):
+            return "UPPER(%s)"
+        return "%s"
+
+    def max_in_list_size(self):
+        return 1000
+
+    def max_name_length(self):
+        return 30
+
+    def pk_default_value(self):
+        return "NULL"
+
+    def prep_for_iexact_query(self, x):
+        return x
+
+    def process_clob(self, value):
+        if value is None:
+            return ''
+        return value.read()
+
+    def quote_name(self, name):
+        # SQL92 requires delimited (quoted) names to be case-sensitive.  When
+        # not quoted, Oracle has case-insensitive behavior for identifiers, but
+        # always defaults to uppercase.
+        # We simplify things by making Oracle identifiers always uppercase.
+        if not name.startswith('"') and not name.endswith('"'):
+            name = '"%s"' % truncate_name(name.upper(), self.max_name_length())
+        # Oracle puts the query text into a (query % args) construct, so % signs
+        # in names need to be escaped. The '%%' will be collapsed back to '%' at
+        # that stage so we aren't really making the name longer here.
+        name = name.replace('%', '%%')
+        return name.upper()
+
+    def random_function_sql(self):
+        return "DBMS_RANDOM.RANDOM"
+
+    def regex_lookup(self, lookup_type):
+        if lookup_type == 'regex':
+            match_option = "'c'"
+        else:
+            match_option = "'i'"
+        return 'REGEXP_LIKE(%%s, %%s, %s)' % match_option
+
+    def return_insert_columns(self, fields):
+        if not fields:
+            return '', ()
+        sql = 'RETURNING %s.%s INTO %%s' % (
+            self.quote_name(fields[0].model._meta.db_table),
+            self.quote_name(fields[0].column),
+        )
+        return sql, (InsertVar(fields[0]),)
+
+    def __foreign_key_constraints(self, table_name, recursive):
+        with self.connection.cursor() as cursor:
+            if recursive:
+                cursor.execute("""
+                    SELECT
+                        user_tables.table_name, rcons.constraint_name
+                    FROM
+                        user_tables
+                    JOIN
+                        user_constraints cons
+                        ON (user_tables.table_name = cons.table_name AND cons.constraint_type = ANY('P', 'U'))
+                    LEFT JOIN
+                        user_constraints rcons
+                        ON (user_tables.table_name = rcons.table_name AND rcons.constraint_type = 'R')
+                    START WITH user_tables.table_name = UPPER(%s)
+                    CONNECT BY NOCYCLE PRIOR cons.constraint_name = rcons.r_constraint_name
+                    GROUP BY
+                        user_tables.table_name, rcons.constraint_name
+                    HAVING user_tables.table_name != UPPER(%s)
+                    ORDER BY MAX(level) DESC
+                """, (table_name, table_name))
+            else:
+                cursor.execute("""
+                    SELECT
+                        cons.table_name, cons.constraint_name
+                    FROM
+                        user_constraints cons
+                    WHERE
+                        cons.constraint_type = 'R'
+                        AND cons.table_name = UPPER(%s)
+                """, (table_name,))
+            return cursor.fetchall()
+
+    @cached_property
+    def _foreign_key_constraints(self):
+        # 512 is large enough to fit the ~330 tables (as of this writing) in
+        # Django's test suite.
+        return lru_cache(maxsize=512)(self.__foreign_key_constraints)
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        if tables:
+            truncated_tables = {table.upper() for table in tables}
+            constraints = set()
+            # Oracle's TRUNCATE CASCADE only works with ON DELETE CASCADE
+            # foreign keys which Django doesn't define. Emulate the
+            # PostgreSQL behavior which truncates all dependent tables by
+            # manually retrieving all foreign key constraints and resolving
+            # dependencies.
+            for table in tables:
+                for foreign_table, constraint in self._foreign_key_constraints(table, recursive=allow_cascade):
+                    if allow_cascade:
+                        truncated_tables.add(foreign_table)
+                    constraints.add((foreign_table, constraint))
+            sql = [
+                "%s %s %s %s %s %s %s %s;" % (
+                    style.SQL_KEYWORD('ALTER'),
+                    style.SQL_KEYWORD('TABLE'),
+                    style.SQL_FIELD(self.quote_name(table)),
+                    style.SQL_KEYWORD('DISABLE'),
+                    style.SQL_KEYWORD('CONSTRAINT'),
+                    style.SQL_FIELD(self.quote_name(constraint)),
+                    style.SQL_KEYWORD('KEEP'),
+                    style.SQL_KEYWORD('INDEX'),
+                ) for table, constraint in constraints
+            ] + [
+                "%s %s %s;" % (
+                    style.SQL_KEYWORD('TRUNCATE'),
+                    style.SQL_KEYWORD('TABLE'),
+                    style.SQL_FIELD(self.quote_name(table)),
+                ) for table in truncated_tables
+            ] + [
+                "%s %s %s %s %s %s;" % (
+                    style.SQL_KEYWORD('ALTER'),
+                    style.SQL_KEYWORD('TABLE'),
+                    style.SQL_FIELD(self.quote_name(table)),
+                    style.SQL_KEYWORD('ENABLE'),
+                    style.SQL_KEYWORD('CONSTRAINT'),
+                    style.SQL_FIELD(self.quote_name(constraint)),
+                ) for table, constraint in constraints
+            ]
+            # Since we've just deleted all the rows, running our sequence
+            # ALTER code will reset the sequence to 0.
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+            return sql
+        else:
+            return []
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        sql = []
+        for sequence_info in sequences:
+            no_autofield_sequence_name = self._get_no_autofield_sequence_name(sequence_info['table'])
+            table = self.quote_name(sequence_info['table'])
+            column = self.quote_name(sequence_info['column'] or 'id')
+            query = self._sequence_reset_sql % {
+                'no_autofield_sequence_name': no_autofield_sequence_name,
+                'table': table,
+                'column': column,
+                'table_name': strip_quotes(table),
+                'column_name': strip_quotes(column),
+            }
+            sql.append(query)
+        return sql
+
+    def sequence_reset_sql(self, style, model_list):
+        from django.db import models
+        output = []
+        query = self._sequence_reset_sql
+        for model in model_list:
+            for f in model._meta.local_fields:
+                if isinstance(f, models.AutoField):
+                    no_autofield_sequence_name = self._get_no_autofield_sequence_name(model._meta.db_table)
+                    table = self.quote_name(model._meta.db_table)
+                    column = self.quote_name(f.column)
+                    output.append(query % {
+                        'no_autofield_sequence_name': no_autofield_sequence_name,
+                        'table': table,
+                        'column': column,
+                        'table_name': strip_quotes(table),
+                        'column_name': strip_quotes(column),
+                    })
+                    # Only one AutoField is allowed per model, so don't
+                    # continue to loop
+                    break
+            for f in model._meta.many_to_many:
+                if not f.remote_field.through:
+                    no_autofield_sequence_name = self._get_no_autofield_sequence_name(f.m2m_db_table())
+                    table = self.quote_name(f.m2m_db_table())
+                    column = self.quote_name('id')
+                    output.append(query % {
+                        'no_autofield_sequence_name': no_autofield_sequence_name,
+                        'table': table,
+                        'column': column,
+                        'table_name': strip_quotes(table),
+                        'column_name': 'ID',
+                    })
+        return output
+
+    def start_transaction_sql(self):
+        return ''
+
+    def tablespace_sql(self, tablespace, inline=False):
+        if inline:
+            return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
+        else:
+            return "TABLESPACE %s" % self.quote_name(tablespace)
+
+    def adapt_datefield_value(self, value):
+        """
+        Transform a date value to an object compatible with what is expected
+        by the backend driver for date columns.
+        The default implementation transforms the date to text, but that is not
+        necessary for Oracle.
+        """
+        return value
+
+    def adapt_datetimefield_value(self, value):
+        """
+        Transform a datetime value to an object compatible with what is expected
+        by the backend driver for datetime columns.
+
+        If naive datetime is passed assumes that is in UTC. Normally Django
+        models.DateTimeField makes sure that if USE_TZ is True passed datetime
+        is timezone aware.
+        """
+
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, 'resolve_expression'):
+            return value
+
+        # cx_Oracle doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = timezone.make_naive(value, self.connection.timezone)
+            else:
+                raise ValueError("Oracle backend does not support timezone-aware datetimes when USE_TZ is False.")
+
+        return Oracle_datetime.from_datetime(value)
+
+    def adapt_timefield_value(self, value):
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, 'resolve_expression'):
+            return value
+
+        if isinstance(value, str):
+            return datetime.datetime.strptime(value, '%H:%M:%S')
+
+        # Oracle doesn't support tz-aware times
+        if timezone.is_aware(value):
+            raise ValueError("Oracle backend does not support timezone-aware times.")
+
+        return Oracle_datetime(1900, 1, 1, value.hour, value.minute,
+                               value.second, value.microsecond)
+
+    def combine_expression(self, connector, sub_expressions):
+        lhs, rhs = sub_expressions
+        if connector == '%%':
+            return 'MOD(%s)' % ','.join(sub_expressions)
+        elif connector == '&':
+            return 'BITAND(%s)' % ','.join(sub_expressions)
+        elif connector == '|':
+            return 'BITAND(-%(lhs)s-1,%(rhs)s)+%(lhs)s' % {'lhs': lhs, 'rhs': rhs}
+        elif connector == '<<':
+            return '(%(lhs)s * POWER(2, %(rhs)s))' % {'lhs': lhs, 'rhs': rhs}
+        elif connector == '>>':
+            return 'FLOOR(%(lhs)s / POWER(2, %(rhs)s))' % {'lhs': lhs, 'rhs': rhs}
+        elif connector == '^':
+            return 'POWER(%s)' % ','.join(sub_expressions)
+        return super().combine_expression(connector, sub_expressions)
+
+    def _get_no_autofield_sequence_name(self, table):
+        """
+        Manually created sequence name to keep backward compatibility for
+        AutoFields that aren't Oracle identity columns.
+        """
+        name_length = self.max_name_length() - 3
+        return '%s_SQ' % truncate_name(strip_quotes(table), name_length).upper()
+
+    def _get_sequence_name(self, cursor, table, pk_name):
+        cursor.execute("""
+            SELECT sequence_name
+            FROM user_tab_identity_cols
+            WHERE table_name = UPPER(%s)
+            AND column_name = UPPER(%s)""", [table, pk_name])
+        row = cursor.fetchone()
+        return self._get_no_autofield_sequence_name(table) if row is None else row[0]
+
+    def bulk_insert_sql(self, fields, placeholder_rows):
+        query = []
+        for row in placeholder_rows:
+            select = []
+            for i, placeholder in enumerate(row):
+                # A model without any fields has fields=[None].
+                if fields[i]:
+                    internal_type = getattr(fields[i], 'target_field', fields[i]).get_internal_type()
+                    placeholder = BulkInsertMapper.types.get(internal_type, '%s') % placeholder
+                # Add columns aliases to the first select to avoid "ORA-00918:
+                # column ambiguously defined" when two or more columns in the
+                # first select have the same value.
+                if not query:
+                    placeholder = '%s col_%s' % (placeholder, i)
+                select.append(placeholder)
+            query.append('SELECT %s FROM DUAL' % ', '.join(select))
+        # Bulk insert to tables with Oracle identity columns causes Oracle to
+        # add sequence.nextval to it. Sequence.nextval cannot be used with the
+        # UNION operator. To prevent incorrect SQL, move UNION to a subquery.
+        return 'SELECT * FROM (%s)' % ' UNION ALL '.join(query)
+
+    def subtract_temporals(self, internal_type, lhs, rhs):
+        if internal_type == 'DateField':
+            lhs_sql, lhs_params = lhs
+            rhs_sql, rhs_params = rhs
+            params = (*lhs_params, *rhs_params)
+            return "NUMTODSINTERVAL(TO_NUMBER(%s - %s), 'DAY')" % (lhs_sql, rhs_sql), params
+        return super().subtract_temporals(internal_type, lhs, rhs)
+
+    def bulk_batch_size(self, fields, objs):
+        """Oracle restricts the number of parameters in a query."""
+        if fields:
+            return self.connection.features.max_query_params // len(fields)
+        return len(objs)
+
+    def conditional_expression_supported_in_where_clause(self, expression):
+        """
+        Oracle supports only EXISTS(...) or filters in the WHERE clause, others
+        must be compared with True.
+        """
+        if isinstance(expression, Exists):
+            return True
+        if isinstance(expression, ExpressionWrapper) and isinstance(expression.expression, Q):
+            return True
+        if isinstance(expression, RawSQL) and expression.conditional:
+            return True
+        return False

venv/lib/python3.8/site-packages/django/db/backends/oracle/schema.py

@@ -0,0 +1,172 @@
+import copy
+import datetime
+import re
+
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.utils import DatabaseError
+
+
+class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
+
+    sql_create_column = "ALTER TABLE %(table)s ADD %(column)s %(definition)s"
+    sql_alter_column_type = "MODIFY %(column)s %(type)s"
+    sql_alter_column_null = "MODIFY %(column)s NULL"
+    sql_alter_column_not_null = "MODIFY %(column)s NOT NULL"
+    sql_alter_column_default = "MODIFY %(column)s DEFAULT %(default)s"
+    sql_alter_column_no_default = "MODIFY %(column)s DEFAULT NULL"
+    sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
+    sql_create_column_inline_fk = 'CONSTRAINT %(name)s REFERENCES %(to_table)s(%(to_column)s)%(deferrable)s'
+    sql_delete_table = "DROP TABLE %(table)s CASCADE CONSTRAINTS"
+    sql_create_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s)%(extra)s"
+
+    def quote_value(self, value):
+        if isinstance(value, (datetime.date, datetime.time, datetime.datetime)):
+            return "'%s'" % value
+        elif isinstance(value, str):
+            return "'%s'" % value.replace("\'", "\'\'").replace('%', '%%')
+        elif isinstance(value, (bytes, bytearray, memoryview)):
+            return "'%s'" % value.hex()
+        elif isinstance(value, bool):
+            return "1" if value else "0"
+        else:
+            return str(value)
+
+    def remove_field(self, model, field):
+        # If the column is an identity column, drop the identity before
+        # removing the field.
+        if self._is_identity_column(model._meta.db_table, field.column):
+            self._drop_identity(model._meta.db_table, field.column)
+        super().remove_field(model, field)
+
+    def delete_model(self, model):
+        # Run superclass action
+        super().delete_model(model)
+        # Clean up manually created sequence.
+        self.execute("""
+            DECLARE
+                i INTEGER;
+            BEGIN
+                SELECT COUNT(1) INTO i FROM USER_SEQUENCES
+                    WHERE SEQUENCE_NAME = '%(sq_name)s';
+                IF i = 1 THEN
+                    EXECUTE IMMEDIATE 'DROP SEQUENCE "%(sq_name)s"';
+                END IF;
+            END;
+        /""" % {'sq_name': self.connection.ops._get_no_autofield_sequence_name(model._meta.db_table)})
+
+    def alter_field(self, model, old_field, new_field, strict=False):
+        try:
+            super().alter_field(model, old_field, new_field, strict)
+        except DatabaseError as e:
+            description = str(e)
+            # If we're changing type to an unsupported type we need a
+            # SQLite-ish workaround
+            if 'ORA-22858' in description or 'ORA-22859' in description:
+                self._alter_field_type_workaround(model, old_field, new_field)
+            # If an identity column is changing to a non-numeric type, drop the
+            # identity first.
+            elif 'ORA-30675' in description:
+                self._drop_identity(model._meta.db_table, old_field.column)
+                self.alter_field(model, old_field, new_field, strict)
+            # If a primary key column is changing to an identity column, drop
+            # the primary key first.
+            elif 'ORA-30673' in description and old_field.primary_key:
+                self._delete_primary_key(model, strict=True)
+                self._alter_field_type_workaround(model, old_field, new_field)
+            else:
+                raise
+
+    def _alter_field_type_workaround(self, model, old_field, new_field):
+        """
+        Oracle refuses to change from some type to other type.
+        What we need to do instead is:
+        - Add a nullable version of the desired field with a temporary name. If
+          the new column is an auto field, then the temporary column can't be
+          nullable.
+        - Update the table to transfer values from old to new
+        - Drop old column
+        - Rename the new column and possibly drop the nullable property
+        """
+        # Make a new field that's like the new one but with a temporary
+        # column name.
+        new_temp_field = copy.deepcopy(new_field)
+        new_temp_field.null = (new_field.get_internal_type() not in ('AutoField', 'BigAutoField', 'SmallAutoField'))
+        new_temp_field.column = self._generate_temp_name(new_field.column)
+        # Add it
+        self.add_field(model, new_temp_field)
+        # Explicit data type conversion
+        # https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf
+        # /Data-Type-Comparison-Rules.html#GUID-D0C5A47E-6F93-4C2D-9E49-4F2B86B359DD
+        new_value = self.quote_name(old_field.column)
+        old_type = old_field.db_type(self.connection)
+        if re.match('^N?CLOB', old_type):
+            new_value = "TO_CHAR(%s)" % new_value
+            old_type = 'VARCHAR2'
+        if re.match('^N?VARCHAR2', old_type):
+            new_internal_type = new_field.get_internal_type()
+            if new_internal_type == 'DateField':
+                new_value = "TO_DATE(%s, 'YYYY-MM-DD')" % new_value
+            elif new_internal_type == 'DateTimeField':
+                new_value = "TO_TIMESTAMP(%s, 'YYYY-MM-DD HH24:MI:SS.FF')" % new_value
+            elif new_internal_type == 'TimeField':
+                # TimeField are stored as TIMESTAMP with a 1900-01-01 date part.
+                new_value = "TO_TIMESTAMP(CONCAT('1900-01-01 ', %s), 'YYYY-MM-DD HH24:MI:SS.FF')" % new_value
+        # Transfer values across
+        self.execute("UPDATE %s set %s=%s" % (
+            self.quote_name(model._meta.db_table),
+            self.quote_name(new_temp_field.column),
+            new_value,
+        ))
+        # Drop the old field
+        self.remove_field(model, old_field)
+        # Rename and possibly make the new field NOT NULL
+        super().alter_field(model, new_temp_field, new_field)
+
+    def normalize_name(self, name):
+        """
+        Get the properly shortened and uppercased identifier as returned by
+        quote_name() but without the quotes.
+        """
+        nn = self.quote_name(name)
+        if nn[0] == '"' and nn[-1] == '"':
+            nn = nn[1:-1]
+        return nn
+
+    def _generate_temp_name(self, for_name):
+        """Generate temporary names for workarounds that need temp columns."""
+        suffix = hex(hash(for_name)).upper()[1:]
+        return self.normalize_name(for_name + "_" + suffix)
+
+    def prepare_default(self, value):
+        return self.quote_value(value)
+
+    def _field_should_be_indexed(self, model, field):
+        create_index = super()._field_should_be_indexed(model, field)
+        db_type = field.db_type(self.connection)
+        if db_type is not None and db_type.lower() in self.connection._limited_data_types:
+            return False
+        return create_index
+
+    def _unique_should_be_added(self, old_field, new_field):
+        return (
+            super()._unique_should_be_added(old_field, new_field) and
+            not self._field_became_primary_key(old_field, new_field)
+        )
+
+    def _is_identity_column(self, table_name, column_name):
+        with self.connection.cursor() as cursor:
+            cursor.execute("""
+                SELECT
+                    CASE WHEN identity_column = 'YES' THEN 1 ELSE 0 END
+                FROM user_tab_cols
+                WHERE table_name = %s AND
+                      column_name = %s
+            """, [self.normalize_name(table_name), self.normalize_name(column_name)])
+            row = cursor.fetchone()
+            return row[0] if row else False
+
+    def _drop_identity(self, table_name, column_name):
+        self.execute('ALTER TABLE %(table)s MODIFY %(column)s DROP IDENTITY' % {
+            'table': self.quote_name(table_name),
+            'column': self.quote_name(column_name),
+        })

venv/lib/python3.8/site-packages/django/db/backends/oracle/utils.py

@@ -0,0 +1,76 @@
+import datetime
+
+from .base import Database
+
+
+class InsertVar:
+    """
+    A late-binding cursor variable that can be passed to Cursor.execute
+    as a parameter, in order to receive the id of the row created by an
+    insert statement.
+    """
+    types = {
+        'AutoField': int,
+        'BigAutoField': int,
+        'SmallAutoField': int,
+        'IntegerField': int,
+        'BigIntegerField': int,
+        'SmallIntegerField': int,
+        'PositiveSmallIntegerField': int,
+        'PositiveIntegerField': int,
+        'FloatField': Database.NATIVE_FLOAT,
+        'DateTimeField': Database.TIMESTAMP,
+        'DateField': Database.Date,
+        'DecimalField': Database.NUMBER,
+    }
+
+    def __init__(self, field):
+        internal_type = getattr(field, 'target_field', field).get_internal_type()
+        self.db_type = self.types.get(internal_type, str)
+
+    def bind_parameter(self, cursor):
+        param = cursor.cursor.var(self.db_type)
+        cursor._insert_id_var = param
+        return param
+
+
+class Oracle_datetime(datetime.datetime):
+    """
+    A datetime object, with an additional class attribute
+    to tell cx_Oracle to save the microseconds too.
+    """
+    input_size = Database.TIMESTAMP
+
+    @classmethod
+    def from_datetime(cls, dt):
+        return Oracle_datetime(
+            dt.year, dt.month, dt.day,
+            dt.hour, dt.minute, dt.second, dt.microsecond,
+        )
+
+
+class BulkInsertMapper:
+    BLOB = 'TO_BLOB(%s)'
+    CLOB = 'TO_CLOB(%s)'
+    DATE = 'TO_DATE(%s)'
+    INTERVAL = 'CAST(%s as INTERVAL DAY(9) TO SECOND(6))'
+    NUMBER = 'TO_NUMBER(%s)'
+    TIMESTAMP = 'TO_TIMESTAMP(%s)'
+
+    types = {
+        'BigIntegerField': NUMBER,
+        'BinaryField': BLOB,
+        'BooleanField': NUMBER,
+        'DateField': DATE,
+        'DateTimeField': TIMESTAMP,
+        'DecimalField': NUMBER,
+        'DurationField': INTERVAL,
+        'FloatField': NUMBER,
+        'IntegerField': NUMBER,
+        'NullBooleanField': NUMBER,
+        'PositiveIntegerField': NUMBER,
+        'PositiveSmallIntegerField': NUMBER,
+        'SmallIntegerField': NUMBER,
+        'TextField': CLOB,
+        'TimeField': TIMESTAMP,
+    }

venv/lib/python3.8/site-packages/django/db/backends/oracle/validation.py

@@ -0,0 +1,22 @@
+from django.core import checks
+from django.db.backends.base.validation import BaseDatabaseValidation
+
+
+class DatabaseValidation(BaseDatabaseValidation):
+    def check_field_type(self, field, field_type):
+        """Oracle doesn't support a database index on some data types."""
+        errors = []
+        if field.db_index and field_type.lower() in self.connection._limited_data_types:
+            errors.append(
+                checks.Warning(
+                    'Oracle does not support a database index on %s columns.'
+                    % field_type,
+                    hint=(
+                        "An index won't be created. Silence this warning if "
+                        "you don't care about it."
+                    ),
+                    obj=field,
+                    id='fields.W162',
+                )
+            )
+        return errors

venv/lib/python3.8/site-packages/django/db/backends/postgresql/base.py

@@ -0,0 +1,326 @@
+"""
+PostgreSQL database backend for Django.
+
+Requires psycopg 2: https://www.psycopg.org/
+"""
+
+import asyncio
+import threading
+import warnings
+
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.db import connections
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.utils import (
+    CursorDebugWrapper as BaseCursorDebugWrapper,
+)
+from django.db.utils import DatabaseError as WrappedDatabaseError
+from django.utils.asyncio import async_unsafe
+from django.utils.functional import cached_property
+from django.utils.safestring import SafeString
+from django.utils.version import get_version_tuple
+
+try:
+    import psycopg2 as Database
+    import psycopg2.extensions
+    import psycopg2.extras
+except ImportError as e:
+    raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)
+
+
+def psycopg2_version():
+    version = psycopg2.__version__.split(' ', 1)[0]
+    return get_version_tuple(version)
+
+
+PSYCOPG2_VERSION = psycopg2_version()
+
+if PSYCOPG2_VERSION < (2, 5, 4):
+    raise ImproperlyConfigured("psycopg2_version 2.5.4 or newer is required; you have %s" % psycopg2.__version__)
+
+
+# Some of these import psycopg2, so import them after checking if it's installed.
+from .client import DatabaseClient                          # NOQA isort:skip
+from .creation import DatabaseCreation                      # NOQA isort:skip
+from .features import DatabaseFeatures                      # NOQA isort:skip
+from .introspection import DatabaseIntrospection            # NOQA isort:skip
+from .operations import DatabaseOperations                  # NOQA isort:skip
+from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
+from .utils import utc_tzinfo_factory                       # NOQA isort:skip
+
+psycopg2.extensions.register_adapter(SafeString, psycopg2.extensions.QuotedString)
+psycopg2.extras.register_uuid()
+
+# Register support for inet[] manually so we don't have to handle the Inet()
+# object on load all the time.
+INETARRAY_OID = 1041
+INETARRAY = psycopg2.extensions.new_array_type(
+    (INETARRAY_OID,),
+    'INETARRAY',
+    psycopg2.extensions.UNICODE,
+)
+psycopg2.extensions.register_type(INETARRAY)
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    vendor = 'postgresql'
+    display_name = 'PostgreSQL'
+    # This dictionary maps Field objects to their associated PostgreSQL column
+    # types, as strings. Column-type strings can contain format strings; they'll
+    # be interpolated against the values of Field.__dict__ before being output.
+    # If a column type is set to None, it won't be included in the output.
+    data_types = {
+        'AutoField': 'serial',
+        'BigAutoField': 'bigserial',
+        'BinaryField': 'bytea',
+        'BooleanField': 'boolean',
+        'CharField': 'varchar(%(max_length)s)',
+        'DateField': 'date',
+        'DateTimeField': 'timestamp with time zone',
+        'DecimalField': 'numeric(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'interval',
+        'FileField': 'varchar(%(max_length)s)',
+        'FilePathField': 'varchar(%(max_length)s)',
+        'FloatField': 'double precision',
+        'IntegerField': 'integer',
+        'BigIntegerField': 'bigint',
+        'IPAddressField': 'inet',
+        'GenericIPAddressField': 'inet',
+        'NullBooleanField': 'boolean',
+        'OneToOneField': 'integer',
+        'PositiveIntegerField': 'integer',
+        'PositiveSmallIntegerField': 'smallint',
+        'SlugField': 'varchar(%(max_length)s)',
+        'SmallAutoField': 'smallserial',
+        'SmallIntegerField': 'smallint',
+        'TextField': 'text',
+        'TimeField': 'time',
+        'UUIDField': 'uuid',
+    }
+    data_type_check_constraints = {
+        'PositiveIntegerField': '"%(column)s" >= 0',
+        'PositiveSmallIntegerField': '"%(column)s" >= 0',
+    }
+    operators = {
+        'exact': '= %s',
+        'iexact': '= UPPER(%s)',
+        'contains': 'LIKE %s',
+        'icontains': 'LIKE UPPER(%s)',
+        'regex': '~ %s',
+        'iregex': '~* %s',
+        'gt': '> %s',
+        'gte': '>= %s',
+        'lt': '< %s',
+        'lte': '<= %s',
+        'startswith': 'LIKE %s',
+        'endswith': 'LIKE %s',
+        'istartswith': 'LIKE UPPER(%s)',
+        'iendswith': 'LIKE UPPER(%s)',
+    }
+
+    # The patterns below are used to generate SQL pattern lookup clauses when
+    # the right-hand side of the lookup isn't a raw string (it might be an expression
+    # or the result of a bilateral transformation).
+    # In those cases, special characters for LIKE operators (e.g. \, *, _) should be
+    # escaped on database side.
+    #
+    # Note: we use str.format() here for readability as '%' is used as a wildcard for
+    # the LIKE operator.
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, E'\\', E'\\\\'), E'%%', E'\\%%'), E'_', E'\\_')"
+    pattern_ops = {
+        'contains': "LIKE '%%' || {} || '%%'",
+        'icontains': "LIKE '%%' || UPPER({}) || '%%'",
+        'startswith': "LIKE {} || '%%'",
+        'istartswith': "LIKE UPPER({}) || '%%'",
+        'endswith': "LIKE '%%' || {}",
+        'iendswith': "LIKE '%%' || UPPER({})",
+    }
+
+    Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+    # PostgreSQL backend-specific attributes.
+    _named_cursor_idx = 0
+
+    def get_connection_params(self):
+        settings_dict = self.settings_dict
+        # None may be used to connect to the default 'postgres' db
+        if settings_dict['NAME'] == '':
+            raise ImproperlyConfigured(
+                "settings.DATABASES is improperly configured. "
+                "Please supply the NAME value.")
+        if len(settings_dict['NAME'] or '') > self.ops.max_name_length():
+            raise ImproperlyConfigured(
+                "The database name '%s' (%d characters) is longer than "
+                "PostgreSQL's limit of %d characters. Supply a shorter NAME "
+                "in settings.DATABASES." % (
+                    settings_dict['NAME'],
+                    len(settings_dict['NAME']),
+                    self.ops.max_name_length(),
+                )
+            )
+        conn_params = {
+            'database': settings_dict['NAME'] or 'postgres',
+            **settings_dict['OPTIONS'],
+        }
+        conn_params.pop('isolation_level', None)
+        if settings_dict['USER']:
+            conn_params['user'] = settings_dict['USER']
+        if settings_dict['PASSWORD']:
+            conn_params['password'] = settings_dict['PASSWORD']
+        if settings_dict['HOST']:
+            conn_params['host'] = settings_dict['HOST']
+        if settings_dict['PORT']:
+            conn_params['port'] = settings_dict['PORT']
+        return conn_params
+
+    @async_unsafe
+    def get_new_connection(self, conn_params):
+        connection = Database.connect(**conn_params)
+
+        # self.isolation_level must be set:
+        # - after connecting to the database in order to obtain the database's
+        #   default when no value is explicitly specified in options.
+        # - before calling _set_autocommit() because if autocommit is on, that
+        #   will set connection.isolation_level to ISOLATION_LEVEL_AUTOCOMMIT.
+        options = self.settings_dict['OPTIONS']
+        try:
+            self.isolation_level = options['isolation_level']
+        except KeyError:
+            self.isolation_level = connection.isolation_level
+        else:
+            # Set the isolation level to the value from OPTIONS.
+            if self.isolation_level != connection.isolation_level:
+                connection.set_session(isolation_level=self.isolation_level)
+
+        return connection
+
+    def ensure_timezone(self):
+        if self.connection is None:
+            return False
+        conn_timezone_name = self.connection.get_parameter_status('TimeZone')
+        timezone_name = self.timezone_name
+        if timezone_name and conn_timezone_name != timezone_name:
+            with self.connection.cursor() as cursor:
+                cursor.execute(self.ops.set_time_zone_sql(), [timezone_name])
+            return True
+        return False
+
+    def init_connection_state(self):
+        self.connection.set_client_encoding('UTF8')
+
+        timezone_changed = self.ensure_timezone()
+        if timezone_changed:
+            # Commit after setting the time zone (see #17062)
+            if not self.get_autocommit():
+                self.connection.commit()
+
+    @async_unsafe
+    def create_cursor(self, name=None):
+        if name:
+            # In autocommit mode, the cursor will be used outside of a
+            # transaction, hence use a holdable cursor.
+            cursor = self.connection.cursor(name, scrollable=False, withhold=self.connection.autocommit)
+        else:
+            cursor = self.connection.cursor()
+        cursor.tzinfo_factory = utc_tzinfo_factory if settings.USE_TZ else None
+        return cursor
+
+    @async_unsafe
+    def chunked_cursor(self):
+        self._named_cursor_idx += 1
+        # Get the current async task
+        # Note that right now this is behind @async_unsafe, so this is
+        # unreachable, but in future we'll start loosening this restriction.
+        # For now, it's here so that every use of "threading" is
+        # also async-compatible.
+        try:
+            if hasattr(asyncio, 'current_task'):
+                # Python 3.7 and up
+                current_task = asyncio.current_task()
+            else:
+                # Python 3.6
+                current_task = asyncio.Task.current_task()
+        except RuntimeError:
+            current_task = None
+        # Current task can be none even if the current_task call didn't error
+        if current_task:
+            task_ident = str(id(current_task))
+        else:
+            task_ident = 'sync'
+        # Use that and the thread ident to get a unique name
+        return self._cursor(
+            name='_django_curs_%d_%s_%d' % (
+                # Avoid reusing name in other threads / tasks
+                threading.current_thread().ident,
+                task_ident,
+                self._named_cursor_idx,
+            )
+        )
+
+    def _set_autocommit(self, autocommit):
+        with self.wrap_database_errors:
+            self.connection.autocommit = autocommit
+
+    def check_constraints(self, table_names=None):
+        """
+        Check constraints by setting them to immediate. Return them to deferred
+        afterward.
+        """
+        self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
+        self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')
+
+    def is_usable(self):
+        try:
+            # Use a psycopg cursor directly, bypassing Django's utilities.
+            self.connection.cursor().execute("SELECT 1")
+        except Database.Error:
+            return False
+        else:
+            return True
+
+    @property
+    def _nodb_connection(self):
+        nodb_connection = super()._nodb_connection
+        try:
+            nodb_connection.ensure_connection()
+        except (Database.DatabaseError, WrappedDatabaseError):
+            warnings.warn(
+                "Normally Django will use a connection to the 'postgres' database "
+                "to avoid running initialization queries against the production "
+                "database when it's not needed (for example, when running tests). "
+                "Django was unable to create a connection to the 'postgres' database "
+                "and will use the first PostgreSQL database instead.",
+                RuntimeWarning
+            )
+            for connection in connections.all():
+                if connection.vendor == 'postgresql' and connection.settings_dict['NAME'] != 'postgres':
+                    return self.__class__(
+                        {**self.settings_dict, 'NAME': connection.settings_dict['NAME']},
+                        alias=self.alias,
+                    )
+        return nodb_connection
+
+    @cached_property
+    def pg_version(self):
+        with self.temporary_connection():
+            return self.connection.server_version
+
+    def make_debug_cursor(self, cursor):
+        return CursorDebugWrapper(cursor, self)
+
+
+class CursorDebugWrapper(BaseCursorDebugWrapper):
+    def copy_expert(self, sql, file, *args):
+        with self.debug_sql(sql):
+            return self.cursor.copy_expert(sql, file, *args)
+
+    def copy_to(self, file, table, *args, **kwargs):
+        with self.debug_sql(sql='COPY %s TO STDOUT' % table):
+            return self.cursor.copy_to(file, table, *args, **kwargs)

venv/lib/python3.8/site-packages/django/db/backends/postgresql/client.py

@@ -0,0 +1,54 @@
+import os
+import signal
+import subprocess
+
+from django.db.backends.base.client import BaseDatabaseClient
+
+
+class DatabaseClient(BaseDatabaseClient):
+    executable_name = 'psql'
+
+    @classmethod
+    def runshell_db(cls, conn_params):
+        args = [cls.executable_name]
+
+        host = conn_params.get('host', '')
+        port = conn_params.get('port', '')
+        dbname = conn_params.get('database', '')
+        user = conn_params.get('user', '')
+        passwd = conn_params.get('password', '')
+        sslmode = conn_params.get('sslmode', '')
+        sslrootcert = conn_params.get('sslrootcert', '')
+        sslcert = conn_params.get('sslcert', '')
+        sslkey = conn_params.get('sslkey', '')
+
+        if user:
+            args += ['-U', user]
+        if host:
+            args += ['-h', host]
+        if port:
+            args += ['-p', str(port)]
+        args += [dbname]
+
+        sigint_handler = signal.getsignal(signal.SIGINT)
+        subprocess_env = os.environ.copy()
+        if passwd:
+            subprocess_env['PGPASSWORD'] = str(passwd)
+        if sslmode:
+            subprocess_env['PGSSLMODE'] = str(sslmode)
+        if sslrootcert:
+            subprocess_env['PGSSLROOTCERT'] = str(sslrootcert)
+        if sslcert:
+            subprocess_env['PGSSLCERT'] = str(sslcert)
+        if sslkey:
+            subprocess_env['PGSSLKEY'] = str(sslkey)
+        try:
+            # Allow SIGINT to pass to psql to abort queries.
+            signal.signal(signal.SIGINT, signal.SIG_IGN)
+            subprocess.run(args, check=True, env=subprocess_env)
+        finally:
+            # Restore the original SIGINT handler.
+            signal.signal(signal.SIGINT, sigint_handler)
+
+    def runshell(self):
+        DatabaseClient.runshell_db(self.connection.get_connection_params())

venv/lib/python3.8/site-packages/django/db/backends/postgresql/creation.py

@@ -0,0 +1,77 @@
+import sys
+
+from psycopg2 import errorcodes
+
+from django.db.backends.base.creation import BaseDatabaseCreation
+from django.db.backends.utils import strip_quotes
+
+
+class DatabaseCreation(BaseDatabaseCreation):
+
+    def _quote_name(self, name):
+        return self.connection.ops.quote_name(name)
+
+    def _get_database_create_suffix(self, encoding=None, template=None):
+        suffix = ""
+        if encoding:
+            suffix += " ENCODING '{}'".format(encoding)
+        if template:
+            suffix += " TEMPLATE {}".format(self._quote_name(template))
+        return suffix and "WITH" + suffix
+
+    def sql_table_creation_suffix(self):
+        test_settings = self.connection.settings_dict['TEST']
+        assert test_settings['COLLATION'] is None, (
+            "PostgreSQL does not support collation setting at database creation time."
+        )
+        return self._get_database_create_suffix(
+            encoding=test_settings['CHARSET'],
+            template=test_settings.get('TEMPLATE'),
+        )
+
+    def _database_exists(self, cursor, database_name):
+        cursor.execute('SELECT 1 FROM pg_catalog.pg_database WHERE datname = %s', [strip_quotes(database_name)])
+        return cursor.fetchone() is not None
+
+    def _execute_create_test_db(self, cursor, parameters, keepdb=False):
+        try:
+            if keepdb and self._database_exists(cursor, parameters['dbname']):
+                # If the database should be kept and it already exists, don't
+                # try to create a new one.
+                return
+            super()._execute_create_test_db(cursor, parameters, keepdb)
+        except Exception as e:
+            if getattr(e.__cause__, 'pgcode', '') != errorcodes.DUPLICATE_DATABASE:
+                # All errors except "database already exists" cancel tests.
+                self.log('Got an error creating the test database: %s' % e)
+                sys.exit(2)
+            elif not keepdb:
+                # If the database should be kept, ignore "database already
+                # exists".
+                raise e
+
+    def _clone_test_db(self, suffix, verbosity, keepdb=False):
+        # CREATE DATABASE ... WITH TEMPLATE ... requires closing connections
+        # to the template database.
+        self.connection.close()
+
+        source_database_name = self.connection.settings_dict['NAME']
+        target_database_name = self.get_test_db_clone_settings(suffix)['NAME']
+        test_db_params = {
+            'dbname': self._quote_name(target_database_name),
+            'suffix': self._get_database_create_suffix(template=source_database_name),
+        }
+        with self._nodb_connection.cursor() as cursor:
+            try:
+                self._execute_create_test_db(cursor, test_db_params, keepdb)
+            except Exception:
+                try:
+                    if verbosity >= 1:
+                        self.log('Destroying old test database for alias %s...' % (
+                            self._get_database_display_str(verbosity, target_database_name),
+                        ))
+                    cursor.execute('DROP DATABASE %(dbname)s' % test_db_params)
+                    self._execute_create_test_db(cursor, test_db_params, keepdb)
+                except Exception as e:
+                    self.log('Got an error cloning the test database: %s' % e)
+                    sys.exit(2)

venv/lib/python3.8/site-packages/django/db/backends/postgresql/features.py

@@ -0,0 +1,70 @@
+import operator
+
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.utils import InterfaceError
+from django.utils.functional import cached_property
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    allows_group_by_selected_pks = True
+    can_return_columns_from_insert = True
+    can_return_multiple_columns_from_insert = True
+    can_return_rows_from_bulk_insert = True
+    has_real_datatype = True
+    has_native_uuid_field = True
+    has_native_duration_field = True
+    can_defer_constraint_checks = True
+    has_select_for_update = True
+    has_select_for_update_nowait = True
+    has_select_for_update_of = True
+    has_select_for_update_skip_locked = True
+    can_release_savepoints = True
+    supports_tablespaces = True
+    supports_transactions = True
+    can_introspect_autofield = True
+    can_introspect_ip_address_field = True
+    can_introspect_materialized_views = True
+    can_introspect_small_integer_field = True
+    can_distinct_on_fields = True
+    can_rollback_ddl = True
+    supports_combined_alters = True
+    nulls_order_largest = True
+    closed_cursor_error_class = InterfaceError
+    has_case_insensitive_like = False
+    greatest_least_ignores_nulls = True
+    can_clone_databases = True
+    supports_temporal_subtraction = True
+    supports_slicing_ordering_in_compound = True
+    create_test_procedure_without_params_sql = """
+        CREATE FUNCTION test_procedure () RETURNS void AS $$
+        DECLARE
+            V_I INTEGER;
+        BEGIN
+            V_I := 1;
+        END;
+    $$ LANGUAGE plpgsql;"""
+    create_test_procedure_with_int_param_sql = """
+        CREATE FUNCTION test_procedure (P_I INTEGER) RETURNS void AS $$
+        DECLARE
+            V_I INTEGER;
+        BEGIN
+            V_I := P_I;
+        END;
+    $$ LANGUAGE plpgsql;"""
+    requires_casted_case_in_updates = True
+    supports_over_clause = True
+    supports_aggregate_filter_clause = True
+    supported_explain_formats = {'JSON', 'TEXT', 'XML', 'YAML'}
+    validates_explain_options = False  # A query will error on invalid options.
+
+    @cached_property
+    def is_postgresql_9_6(self):
+        return self.connection.pg_version >= 90600
+
+    @cached_property
+    def is_postgresql_10(self):
+        return self.connection.pg_version >= 100000
+
+    has_brin_autosummarize = property(operator.attrgetter('is_postgresql_10'))
+    has_phraseto_tsquery = property(operator.attrgetter('is_postgresql_9_6'))
+    supports_table_partitions = property(operator.attrgetter('is_postgresql_10'))

venv/lib/python3.8/site-packages/django/db/backends/postgresql/introspection.py

@@ -0,0 +1,224 @@
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
+)
+from django.db.models.indexes import Index
+
+
+class DatabaseIntrospection(BaseDatabaseIntrospection):
+    # Maps type codes to Django Field types.
+    data_types_reverse = {
+        16: 'BooleanField',
+        17: 'BinaryField',
+        20: 'BigIntegerField',
+        21: 'SmallIntegerField',
+        23: 'IntegerField',
+        25: 'TextField',
+        700: 'FloatField',
+        701: 'FloatField',
+        869: 'GenericIPAddressField',
+        1042: 'CharField',  # blank-padded
+        1043: 'CharField',
+        1082: 'DateField',
+        1083: 'TimeField',
+        1114: 'DateTimeField',
+        1184: 'DateTimeField',
+        1186: 'DurationField',
+        1266: 'TimeField',
+        1700: 'DecimalField',
+        2950: 'UUIDField',
+    }
+
+    ignored_tables = []
+
+    def get_field_type(self, data_type, description):
+        field_type = super().get_field_type(data_type, description)
+        if description.default and 'nextval' in description.default:
+            if field_type == 'IntegerField':
+                return 'AutoField'
+            elif field_type == 'BigIntegerField':
+                return 'BigAutoField'
+            elif field_type == 'SmallIntegerField':
+                return 'SmallAutoField'
+        return field_type
+
+    def get_table_list(self, cursor):
+        """Return a list of table and view names in the current database."""
+        cursor.execute("""
+            SELECT c.relname,
+            CASE WHEN {} THEN 'p' WHEN c.relkind IN ('m', 'v') THEN 'v' ELSE 't' END
+            FROM pg_catalog.pg_class c
+            LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
+            WHERE c.relkind IN ('f', 'm', 'p', 'r', 'v')
+                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
+                AND pg_catalog.pg_table_is_visible(c.oid)
+        """.format('c.relispartition' if self.connection.features.supports_table_partitions else 'FALSE'))
+        return [TableInfo(*row) for row in cursor.fetchall() if row[0] not in self.ignored_tables]
+
+    def get_table_description(self, cursor, table_name):
+        """
+        Return a description of the table with the DB-API cursor.description
+        interface.
+        """
+        # Query the pg_catalog tables as cursor.description does not reliably
+        # return the nullable property and information_schema.columns does not
+        # contain details of materialized views.
+        cursor.execute("""
+            SELECT
+                a.attname AS column_name,
+                NOT (a.attnotnull OR (t.typtype = 'd' AND t.typnotnull)) AS is_nullable,
+                pg_get_expr(ad.adbin, ad.adrelid) AS column_default
+            FROM pg_attribute a
+            LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum = ad.adnum
+            JOIN pg_type t ON a.atttypid = t.oid
+            JOIN pg_class c ON a.attrelid = c.oid
+            JOIN pg_namespace n ON c.relnamespace = n.oid
+            WHERE c.relkind IN ('f', 'm', 'p', 'r', 'v')
+                AND c.relname = %s
+                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
+                AND pg_catalog.pg_table_is_visible(c.oid)
+        """, [table_name])
+        field_map = {line[0]: line[1:] for line in cursor.fetchall()}
+        cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
+        return [
+            FieldInfo(
+                line.name,
+                line.type_code,
+                line.display_size,
+                line.internal_size,
+                line.precision,
+                line.scale,
+                *field_map[line.name],
+            )
+            for line in cursor.description
+        ]
+
+    def get_sequences(self, cursor, table_name, table_fields=()):
+        cursor.execute("""
+            SELECT s.relname as sequence_name, col.attname
+            FROM pg_class s
+                JOIN pg_namespace sn ON sn.oid = s.relnamespace
+                JOIN pg_depend d ON d.refobjid = s.oid AND d.refclassid = 'pg_class'::regclass
+                JOIN pg_attrdef ad ON ad.oid = d.objid AND d.classid = 'pg_attrdef'::regclass
+                JOIN pg_attribute col ON col.attrelid = ad.adrelid AND col.attnum = ad.adnum
+                JOIN pg_class tbl ON tbl.oid = ad.adrelid
+            WHERE s.relkind = 'S'
+              AND d.deptype in ('a', 'n')
+              AND pg_catalog.pg_table_is_visible(tbl.oid)
+              AND tbl.relname = %s
+        """, [table_name])
+        return [
+            {'name': row[0], 'table': table_name, 'column': row[1]}
+            for row in cursor.fetchall()
+        ]
+
+    def get_relations(self, cursor, table_name):
+        """
+        Return a dictionary of {field_name: (field_name_other_table, other_table)}
+        representing all relationships to the given table.
+        """
+        return {row[0]: (row[2], row[1]) for row in self.get_key_columns(cursor, table_name)}
+
+    def get_key_columns(self, cursor, table_name):
+        cursor.execute("""
+            SELECT a1.attname, c2.relname, a2.attname
+            FROM pg_constraint con
+            LEFT JOIN pg_class c1 ON con.conrelid = c1.oid
+            LEFT JOIN pg_class c2 ON con.confrelid = c2.oid
+            LEFT JOIN pg_attribute a1 ON c1.oid = a1.attrelid AND a1.attnum = con.conkey[1]
+            LEFT JOIN pg_attribute a2 ON c2.oid = a2.attrelid AND a2.attnum = con.confkey[1]
+            WHERE
+                c1.relname = %s AND
+                con.contype = 'f' AND
+                c1.relnamespace = c2.relnamespace AND
+                pg_catalog.pg_table_is_visible(c1.oid)
+        """, [table_name])
+        return cursor.fetchall()
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieve any constraints or keys (unique, pk, fk, check, index) across
+        one or more columns. Also retrieve the definition of expression-based
+        indexes.
+        """
+        constraints = {}
+        # Loop over the key table, collecting things as constraints. The column
+        # array must return column names in the same order in which they were
+        # created.
+        cursor.execute("""
+            SELECT
+                c.conname,
+                array(
+                    SELECT attname
+                    FROM unnest(c.conkey) WITH ORDINALITY cols(colid, arridx)
+                    JOIN pg_attribute AS ca ON cols.colid = ca.attnum
+                    WHERE ca.attrelid = c.conrelid
+                    ORDER BY cols.arridx
+                ),
+                c.contype,
+                (SELECT fkc.relname || '.' || fka.attname
+                FROM pg_attribute AS fka
+                JOIN pg_class AS fkc ON fka.attrelid = fkc.oid
+                WHERE fka.attrelid = c.confrelid AND fka.attnum = c.confkey[1]),
+                cl.reloptions
+            FROM pg_constraint AS c
+            JOIN pg_class AS cl ON c.conrelid = cl.oid
+            WHERE cl.relname = %s AND pg_catalog.pg_table_is_visible(cl.oid)
+        """, [table_name])
+        for constraint, columns, kind, used_cols, options in cursor.fetchall():
+            constraints[constraint] = {
+                "columns": columns,
+                "primary_key": kind == "p",
+                "unique": kind in ["p", "u"],
+                "foreign_key": tuple(used_cols.split(".", 1)) if kind == "f" else None,
+                "check": kind == "c",
+                "index": False,
+                "definition": None,
+                "options": options,
+            }
+        # Now get indexes
+        cursor.execute("""
+            SELECT
+                indexname, array_agg(attname ORDER BY arridx), indisunique, indisprimary,
+                array_agg(ordering ORDER BY arridx), amname, exprdef, s2.attoptions
+            FROM (
+                SELECT
+                    c2.relname as indexname, idx.*, attr.attname, am.amname,
+                    CASE
+                        WHEN idx.indexprs IS NOT NULL THEN
+                            pg_get_indexdef(idx.indexrelid)
+                    END AS exprdef,
+                    CASE am.amname
+                        WHEN 'btree' THEN
+                            CASE (option & 1)
+                                WHEN 1 THEN 'DESC' ELSE 'ASC'
+                            END
+                    END as ordering,
+                    c2.reloptions as attoptions
+                FROM (
+                    SELECT *
+                    FROM pg_index i, unnest(i.indkey, i.indoption) WITH ORDINALITY koi(key, option, arridx)
+                ) idx
+                LEFT JOIN pg_class c ON idx.indrelid = c.oid
+                LEFT JOIN pg_class c2 ON idx.indexrelid = c2.oid
+                LEFT JOIN pg_am am ON c2.relam = am.oid
+                LEFT JOIN pg_attribute attr ON attr.attrelid = c.oid AND attr.attnum = idx.key
+                WHERE c.relname = %s AND pg_catalog.pg_table_is_visible(c.oid)
+            ) s2
+            GROUP BY indexname, indisunique, indisprimary, amname, exprdef, attoptions;
+        """, [table_name])
+        for index, columns, unique, primary, orders, type_, definition, options in cursor.fetchall():
+            if index not in constraints:
+                basic_index = type_ == 'btree' and not index.endswith('_btree') and options is None
+                constraints[index] = {
+                    "columns": columns if columns != [None] else [],
+                    "orders": orders if orders != [None] else [],
+                    "primary_key": primary,
+                    "unique": unique,
+                    "foreign_key": None,
+                    "check": False,
+                    "index": True,
+                    "type": Index.suffix if basic_index else type_,
+                    "definition": definition,
+                    "options": options,
+                }
+        return constraints

venv/lib/python3.8/site-packages/django/db/backends/postgresql/operations.py

@@ -0,0 +1,300 @@
+from psycopg2.extras import Inet
+
+from django.conf import settings
+from django.db import NotSupportedError
+from django.db.backends.base.operations import BaseDatabaseOperations
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    cast_char_field_without_max_length = 'varchar'
+    explain_prefix = 'EXPLAIN'
+    cast_data_types = {
+        'AutoField': 'integer',
+        'BigAutoField': 'bigint',
+        'SmallAutoField': 'smallint',
+    }
+
+    def unification_cast_sql(self, output_field):
+        internal_type = output_field.get_internal_type()
+        if internal_type in ("GenericIPAddressField", "IPAddressField", "TimeField", "UUIDField"):
+            # PostgreSQL will resolve a union as type 'text' if input types are
+            # 'unknown'.
+            # https://www.postgresql.org/docs/current/typeconv-union-case.html
+            # These fields cannot be implicitly cast back in the default
+            # PostgreSQL configuration so we need to explicitly cast them.
+            # We must also remove components of the type within brackets:
+            # varchar(255) -> varchar.
+            return 'CAST(%%s AS %s)' % output_field.db_type(self.connection).split('(')[0]
+        return '%s'
+
+    def date_extract_sql(self, lookup_type, field_name):
+        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
+        if lookup_type == 'week_day':
+            # For consistency across backends, we return Sunday=1, Saturday=7.
+            return "EXTRACT('dow' FROM %s) + 1" % field_name
+        elif lookup_type == 'iso_year':
+            return "EXTRACT('isoyear' FROM %s)" % field_name
+        else:
+            return "EXTRACT('%s' FROM %s)" % (lookup_type, field_name)
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
+        return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
+
+    def _prepare_tzname_delta(self, tzname):
+        if '+' in tzname:
+            return tzname.replace('+', '-')
+        elif '-' in tzname:
+            return tzname.replace('-', '+')
+        return tzname
+
+    def _convert_field_to_tz(self, field_name, tzname):
+        if settings.USE_TZ:
+            field_name = "%s AT TIME ZONE '%s'" % (field_name, self._prepare_tzname_delta(tzname))
+        return field_name
+
+    def datetime_cast_date_sql(self, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return '(%s)::date' % field_name
+
+    def datetime_cast_time_sql(self, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return '(%s)::time' % field_name
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return self.date_extract_sql(lookup_type, field_name)
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
+        return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
+
+    def time_trunc_sql(self, lookup_type, field_name):
+        return "DATE_TRUNC('%s', %s)::time" % (lookup_type, field_name)
+
+    def deferrable_sql(self):
+        return " DEFERRABLE INITIALLY DEFERRED"
+
+    def fetch_returned_insert_rows(self, cursor):
+        """
+        Given a cursor object that has just performed an INSERT...RETURNING
+        statement into a table, return the tuple of returned data.
+        """
+        return cursor.fetchall()
+
+    def lookup_cast(self, lookup_type, internal_type=None):
+        lookup = '%s'
+
+        # Cast text lookups to text to allow things like filter(x__contains=4)
+        if lookup_type in ('iexact', 'contains', 'icontains', 'startswith',
+                           'istartswith', 'endswith', 'iendswith', 'regex', 'iregex'):
+            if internal_type in ('IPAddressField', 'GenericIPAddressField'):
+                lookup = "HOST(%s)"
+            elif internal_type in ('CICharField', 'CIEmailField', 'CITextField'):
+                lookup = '%s::citext'
+            else:
+                lookup = "%s::text"
+
+        # Use UPPER(x) for case-insensitive lookups; it's faster.
+        if lookup_type in ('iexact', 'icontains', 'istartswith', 'iendswith'):
+            lookup = 'UPPER(%s)' % lookup
+
+        return lookup
+
+    def no_limit_value(self):
+        return None
+
+    def prepare_sql_script(self, sql):
+        return [sql]
+
+    def quote_name(self, name):
+        if name.startswith('"') and name.endswith('"'):
+            return name  # Quoting once is enough.
+        return '"%s"' % name
+
+    def set_time_zone_sql(self):
+        return "SET TIME ZONE %s"
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        if tables:
+            # Perform a single SQL 'TRUNCATE x, y, z...;' statement.  It allows
+            # us to truncate tables referenced by a foreign key in any other
+            # table.
+            tables_sql = ', '.join(
+                style.SQL_FIELD(self.quote_name(table)) for table in tables)
+            if allow_cascade:
+                sql = ['%s %s %s;' % (
+                    style.SQL_KEYWORD('TRUNCATE'),
+                    tables_sql,
+                    style.SQL_KEYWORD('CASCADE'),
+                )]
+            else:
+                sql = ['%s %s;' % (
+                    style.SQL_KEYWORD('TRUNCATE'),
+                    tables_sql,
+                )]
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+            return sql
+        else:
+            return []
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        # 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL statements
+        # to reset sequence indices
+        sql = []
+        for sequence_info in sequences:
+            table_name = sequence_info['table']
+            # 'id' will be the case if it's an m2m using an autogenerated
+            # intermediate table (see BaseDatabaseIntrospection.sequence_list).
+            column_name = sequence_info['column'] or 'id'
+            sql.append("%s setval(pg_get_serial_sequence('%s','%s'), 1, false);" % (
+                style.SQL_KEYWORD('SELECT'),
+                style.SQL_TABLE(self.quote_name(table_name)),
+                style.SQL_FIELD(column_name),
+            ))
+        return sql
+
+    def tablespace_sql(self, tablespace, inline=False):
+        if inline:
+            return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
+        else:
+            return "TABLESPACE %s" % self.quote_name(tablespace)
+
+    def sequence_reset_sql(self, style, model_list):
+        from django.db import models
+        output = []
+        qn = self.quote_name
+        for model in model_list:
+            # Use `coalesce` to set the sequence for each model to the max pk value if there are records,
+            # or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true
+            # if there are records (as the max pk value is already in use), otherwise set it to false.
+            # Use pg_get_serial_sequence to get the underlying sequence name from the table name
+            # and column name (available since PostgreSQL 8)
+
+            for f in model._meta.local_fields:
+                if isinstance(f, models.AutoField):
+                    output.append(
+                        "%s setval(pg_get_serial_sequence('%s','%s'), "
+                        "coalesce(max(%s), 1), max(%s) %s null) %s %s;" % (
+                            style.SQL_KEYWORD('SELECT'),
+                            style.SQL_TABLE(qn(model._meta.db_table)),
+                            style.SQL_FIELD(f.column),
+                            style.SQL_FIELD(qn(f.column)),
+                            style.SQL_FIELD(qn(f.column)),
+                            style.SQL_KEYWORD('IS NOT'),
+                            style.SQL_KEYWORD('FROM'),
+                            style.SQL_TABLE(qn(model._meta.db_table)),
+                        )
+                    )
+                    break  # Only one AutoField is allowed per model, so don't bother continuing.
+            for f in model._meta.many_to_many:
+                if not f.remote_field.through:
+                    output.append(
+                        "%s setval(pg_get_serial_sequence('%s','%s'), "
+                        "coalesce(max(%s), 1), max(%s) %s null) %s %s;" % (
+                            style.SQL_KEYWORD('SELECT'),
+                            style.SQL_TABLE(qn(f.m2m_db_table())),
+                            style.SQL_FIELD('id'),
+                            style.SQL_FIELD(qn('id')),
+                            style.SQL_FIELD(qn('id')),
+                            style.SQL_KEYWORD('IS NOT'),
+                            style.SQL_KEYWORD('FROM'),
+                            style.SQL_TABLE(qn(f.m2m_db_table()))
+                        )
+                    )
+        return output
+
+    def prep_for_iexact_query(self, x):
+        return x
+
+    def max_name_length(self):
+        """
+        Return the maximum length of an identifier.
+
+        The maximum length of an identifier is 63 by default, but can be
+        changed by recompiling PostgreSQL after editing the NAMEDATALEN
+        macro in src/include/pg_config_manual.h.
+
+        This implementation returns 63, but can be overridden by a custom
+        database backend that inherits most of its behavior from this one.
+        """
+        return 63
+
+    def distinct_sql(self, fields, params):
+        if fields:
+            params = [param for param_list in params for param in param_list]
+            return (['DISTINCT ON (%s)' % ', '.join(fields)], params)
+        else:
+            return ['DISTINCT'], []
+
+    def last_executed_query(self, cursor, sql, params):
+        # https://www.psycopg.org/docs/cursor.html#cursor.query
+        # The query attribute is a Psycopg extension to the DB API 2.0.
+        if cursor.query is not None:
+            return cursor.query.decode()
+        return None
+
+    def return_insert_columns(self, fields):
+        if not fields:
+            return '', ()
+        columns = [
+            '%s.%s' % (
+                self.quote_name(field.model._meta.db_table),
+                self.quote_name(field.column),
+            ) for field in fields
+        ]
+        return 'RETURNING %s' % ', '.join(columns), ()
+
+    def bulk_insert_sql(self, fields, placeholder_rows):
+        placeholder_rows_sql = (", ".join(row) for row in placeholder_rows)
+        values_sql = ", ".join("(%s)" % sql for sql in placeholder_rows_sql)
+        return "VALUES " + values_sql
+
+    def adapt_datefield_value(self, value):
+        return value
+
+    def adapt_datetimefield_value(self, value):
+        return value
+
+    def adapt_timefield_value(self, value):
+        return value
+
+    def adapt_ipaddressfield_value(self, value):
+        if value:
+            return Inet(value)
+        return None
+
+    def subtract_temporals(self, internal_type, lhs, rhs):
+        if internal_type == 'DateField':
+            lhs_sql, lhs_params = lhs
+            rhs_sql, rhs_params = rhs
+            params = (*lhs_params, *rhs_params)
+            return "(interval '1 day' * (%s - %s))" % (lhs_sql, rhs_sql), params
+        return super().subtract_temporals(internal_type, lhs, rhs)
+
+    def window_frame_range_start_end(self, start=None, end=None):
+        start_, end_ = super().window_frame_range_start_end(start, end)
+        if (start and start < 0) or (end and end > 0):
+            raise NotSupportedError(
+                'PostgreSQL only supports UNBOUNDED together with PRECEDING '
+                'and FOLLOWING.'
+            )
+        return start_, end_
+
+    def explain_query_prefix(self, format=None, **options):
+        prefix = super().explain_query_prefix(format)
+        extra = {}
+        if format:
+            extra['FORMAT'] = format
+        if options:
+            extra.update({
+                name.upper(): 'true' if value else 'false'
+                for name, value in options.items()
+            })
+        if extra:
+            prefix += ' (%s)' % ', '.join('%s %s' % i for i in extra.items())
+        return prefix
+
+    def ignore_conflicts_suffix_sql(self, ignore_conflicts=None):
+        return 'ON CONFLICT DO NOTHING' if ignore_conflicts else super().ignore_conflicts_suffix_sql(ignore_conflicts)

venv/lib/python3.8/site-packages/django/db/backends/postgresql/schema.py

@@ -0,0 +1,192 @@
+import psycopg2
+
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.backends.ddl_references import IndexColumns
+from django.db.backends.utils import strip_quotes
+
+
+class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
+
+    sql_create_sequence = "CREATE SEQUENCE %(sequence)s"
+    sql_delete_sequence = "DROP SEQUENCE IF EXISTS %(sequence)s CASCADE"
+    sql_set_sequence_max = "SELECT setval('%(sequence)s', MAX(%(column)s)) FROM %(table)s"
+    sql_set_sequence_owner = 'ALTER SEQUENCE %(sequence)s OWNED BY %(table)s.%(column)s'
+
+    sql_create_index = "CREATE INDEX %(name)s ON %(table)s%(using)s (%(columns)s)%(extra)s%(condition)s"
+    sql_create_index_concurrently = (
+        "CREATE INDEX CONCURRENTLY %(name)s ON %(table)s%(using)s (%(columns)s)%(extra)s%(condition)s"
+    )
+    sql_delete_index = "DROP INDEX IF EXISTS %(name)s"
+    sql_delete_index_concurrently = "DROP INDEX CONCURRENTLY IF EXISTS %(name)s"
+
+    # Setting the constraint to IMMEDIATE to allow changing data in the same
+    # transaction.
+    sql_create_column_inline_fk = (
+        'CONSTRAINT %(name)s REFERENCES %(to_table)s(%(to_column)s)%(deferrable)s'
+        '; SET CONSTRAINTS %(name)s IMMEDIATE'
+    )
+    # Setting the constraint to IMMEDIATE runs any deferred checks to allow
+    # dropping it in the same transaction.
+    sql_delete_fk = "SET CONSTRAINTS %(name)s IMMEDIATE; ALTER TABLE %(table)s DROP CONSTRAINT %(name)s"
+
+    sql_delete_procedure = 'DROP FUNCTION %(procedure)s(%(param_types)s)'
+
+    def quote_value(self, value):
+        if isinstance(value, str):
+            value = value.replace('%', '%%')
+        # getquoted() returns a quoted bytestring of the adapted value.
+        return psycopg2.extensions.adapt(value).getquoted().decode()
+
+    def _field_indexes_sql(self, model, field):
+        output = super()._field_indexes_sql(model, field)
+        like_index_statement = self._create_like_index_sql(model, field)
+        if like_index_statement is not None:
+            output.append(like_index_statement)
+        return output
+
+    def _field_data_type(self, field):
+        if field.is_relation:
+            return field.rel_db_type(self.connection)
+        return self.connection.data_types.get(
+            field.get_internal_type(),
+            field.db_type(self.connection),
+        )
+
+    def _create_like_index_sql(self, model, field):
+        """
+        Return the statement to create an index with varchar operator pattern
+        when the column type is 'varchar' or 'text', otherwise return None.
+        """
+        db_type = field.db_type(connection=self.connection)
+        if db_type is not None and (field.db_index or field.unique):
+            # Fields with database column types of `varchar` and `text` need
+            # a second index that specifies their operator class, which is
+            # needed when performing correct LIKE queries outside the
+            # C locale. See #12234.
+            #
+            # The same doesn't apply to array fields such as varchar[size]
+            # and text[size], so skip them.
+            if '[' in db_type:
+                return None
+            if db_type.startswith('varchar'):
+                return self._create_index_sql(model, [field], suffix='_like', opclasses=['varchar_pattern_ops'])
+            elif db_type.startswith('text'):
+                return self._create_index_sql(model, [field], suffix='_like', opclasses=['text_pattern_ops'])
+        return None
+
+    def _alter_column_type_sql(self, model, old_field, new_field, new_type):
+        self.sql_alter_column_type = 'ALTER COLUMN %(column)s TYPE %(type)s'
+        # Cast when data type changed.
+        if self._field_data_type(old_field) != self._field_data_type(new_field):
+            self.sql_alter_column_type += ' USING %(column)s::%(type)s'
+        # Make ALTER TYPE with SERIAL make sense.
+        table = strip_quotes(model._meta.db_table)
+        serial_fields_map = {'bigserial': 'bigint', 'serial': 'integer', 'smallserial': 'smallint'}
+        if new_type.lower() in serial_fields_map:
+            column = strip_quotes(new_field.column)
+            sequence_name = "%s_%s_seq" % (table, column)
+            return (
+                (
+                    self.sql_alter_column_type % {
+                        "column": self.quote_name(column),
+                        "type": serial_fields_map[new_type.lower()],
+                    },
+                    [],
+                ),
+                [
+                    (
+                        self.sql_delete_sequence % {
+                            "sequence": self.quote_name(sequence_name),
+                        },
+                        [],
+                    ),
+                    (
+                        self.sql_create_sequence % {
+                            "sequence": self.quote_name(sequence_name),
+                        },
+                        [],
+                    ),
+                    (
+                        self.sql_alter_column % {
+                            "table": self.quote_name(table),
+                            "changes": self.sql_alter_column_default % {
+                                "column": self.quote_name(column),
+                                "default": "nextval('%s')" % self.quote_name(sequence_name),
+                            }
+                        },
+                        [],
+                    ),
+                    (
+                        self.sql_set_sequence_max % {
+                            "table": self.quote_name(table),
+                            "column": self.quote_name(column),
+                            "sequence": self.quote_name(sequence_name),
+                        },
+                        [],
+                    ),
+                    (
+                        self.sql_set_sequence_owner % {
+                            'table': self.quote_name(table),
+                            'column': self.quote_name(column),
+                            'sequence': self.quote_name(sequence_name),
+                        },
+                        [],
+                    ),
+                ],
+            )
+        else:
+            return super()._alter_column_type_sql(model, old_field, new_field, new_type)
+
+    def _alter_field(self, model, old_field, new_field, old_type, new_type,
+                     old_db_params, new_db_params, strict=False):
+        # Drop indexes on varchar/text/citext columns that are changing to a
+        # different type.
+        if (old_field.db_index or old_field.unique) and (
+            (old_type.startswith('varchar') and not new_type.startswith('varchar')) or
+            (old_type.startswith('text') and not new_type.startswith('text')) or
+            (old_type.startswith('citext') and not new_type.startswith('citext'))
+        ):
+            index_name = self._create_index_name(model._meta.db_table, [old_field.column], suffix='_like')
+            self.execute(self._delete_index_sql(model, index_name))
+
+        super()._alter_field(
+            model, old_field, new_field, old_type, new_type, old_db_params,
+            new_db_params, strict,
+        )
+        # Added an index? Create any PostgreSQL-specific indexes.
+        if ((not (old_field.db_index or old_field.unique) and new_field.db_index) or
+                (not old_field.unique and new_field.unique)):
+            like_index_statement = self._create_like_index_sql(model, new_field)
+            if like_index_statement is not None:
+                self.execute(like_index_statement)
+
+        # Removed an index? Drop any PostgreSQL-specific indexes.
+        if old_field.unique and not (new_field.db_index or new_field.unique):
+            index_to_remove = self._create_index_name(model._meta.db_table, [old_field.column], suffix='_like')
+            self.execute(self._delete_index_sql(model, index_to_remove))
+
+    def _index_columns(self, table, columns, col_suffixes, opclasses):
+        if opclasses:
+            return IndexColumns(table, columns, self.quote_name, col_suffixes=col_suffixes, opclasses=opclasses)
+        return super()._index_columns(table, columns, col_suffixes, opclasses)
+
+    def add_index(self, model, index, concurrently=False):
+        self.execute(index.create_sql(model, self, concurrently=concurrently), params=None)
+
+    def remove_index(self, model, index, concurrently=False):
+        self.execute(index.remove_sql(model, self, concurrently=concurrently))
+
+    def _delete_index_sql(self, model, name, sql=None, concurrently=False):
+        sql = self.sql_delete_index_concurrently if concurrently else self.sql_delete_index
+        return super()._delete_index_sql(model, name, sql)
+
+    def _create_index_sql(
+        self, model, fields, *, name=None, suffix='', using='',
+        db_tablespace=None, col_suffixes=(), sql=None, opclasses=(),
+        condition=None, concurrently=False,
+    ):
+        sql = self.sql_create_index if not concurrently else self.sql_create_index_concurrently
+        return super()._create_index_sql(
+            model, fields, name=name, suffix=suffix, using=using, db_tablespace=db_tablespace,
+            col_suffixes=col_suffixes, sql=sql, opclasses=opclasses, condition=condition,
+        )

venv/lib/python3.8/site-packages/django/db/backends/postgresql/utils.py

@@ -0,0 +1,7 @@
+from django.utils.timezone import utc
+
+
+def utc_tzinfo_factory(offset):
+    if offset != 0:
+        raise AssertionError("database connection isn't set to UTC")
+    return utc

venv/lib/python3.8/site-packages/django/db/backends/signals.py

@@ -0,0 +1,3 @@
+from django.dispatch import Signal
+
+connection_created = Signal(providing_args=["connection"])