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import importlib
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.db import DEFAULT_DB_ALIAS, connections
from django.db.backends.postgresql.base import DatabaseWrapper
from django.db.backends.postgresql.introspection import ( # type: ignore[import]
DatabaseIntrospection,
)
from django.db.backends.postgresql.operations import DatabaseOperations
from django.db.backends.postgresql.schema import ( # type: ignore[import]
DatabaseSchemaEditor,
)
from django.db.backends.postgresql.base import ( # isort:skip
DatabaseWrapper as Psycopg2DatabaseWrapper,
)
def base_backend_instance():
"""Gets an instance of the base class for the custom database back-end.
This should be the Django PostgreSQL back-end. However,
some people are already using a custom back-end from
another package. We are nice people and expose an option
that allows them to configure the back-end we base upon.
As long as the specified base eventually also has
the PostgreSQL back-end as a base, then everything should
work as intended.
We create an instance to inspect what classes to subclass
because not all back-ends set properties such as `ops_class`
properly. The PostGIS back-end is a good example.
"""
base_class_name = getattr(
settings,
"POSTGRES_EXTRA_DB_BACKEND_BASE",
"django.db.backends.postgresql",
)
base_class_module = importlib.import_module(base_class_name + ".base")
base_class = getattr(base_class_module, "DatabaseWrapper", None)
if not base_class:
raise ImproperlyConfigured(
(
"'%s' is not a valid database back-end."
" The module does not define a DatabaseWrapper class."
" Check the value of POSTGRES_EXTRA_DB_BACKEND_BASE."
)
% base_class_name
)
if isinstance(base_class, Psycopg2DatabaseWrapper):
raise ImproperlyConfigured(
(
"'%s' is not a valid database back-end."
" It does inherit from the PostgreSQL back-end."
" Check the value of POSTGRES_EXTRA_DB_BACKEND_BASE."
)
% base_class_name
)
base_instance = base_class(connections.databases[DEFAULT_DB_ALIAS])
if base_instance.connection:
raise ImproperlyConfigured(
(
"'%s' establishes a connection during initialization."
" This is not expected and can lead to more connections"
" being established than neccesarry."
)
% base_class_name
)
return base_instance
def backend() -> DatabaseWrapper:
"""Gets the base class for the database back-end."""
return base_backend_instance().__class__
def schema_editor() -> DatabaseSchemaEditor:
"""Gets the base class for the schema editor.
We have to use the configured base back-end's schema editor for
this.
"""
return base_backend_instance().SchemaEditorClass
def introspection() -> DatabaseIntrospection:
"""Gets the base class for the introspection class.
We have to use the configured base back-end's introspection class
for this.
"""
return base_backend_instance().introspection.__class__
def operations() -> DatabaseOperations:
"""Gets the base class for the operations class.
We have to use the configured base back-end's operations class for
this.
"""
return base_backend_instance().ops.__class__
|
