Source code for django.db.utils
import pkgutil
from importlib import import_module
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
# For backwards compatibility with Django < 3.2
from django.utils.connection import ConnectionDoesNotExist # NOQA: F401
from django.utils.connection import BaseConnectionHandler
from django.utils.functional import cached_property
from django.utils.module_loading import import_string
DEFAULT_DB_ALIAS = "default"
DJANGO_VERSION_PICKLE_KEY = "_django_version"
class DatabaseErrorWrapper:
"""
Context manager and decorator that reraises backend-specific database
exceptions using Django's common wrappers.
"""
def __init__(self, wrapper):
"""
wrapper is a database wrapper.
It must have a Database attribute defining PEP-249 exceptions.
"""
self.wrapper = wrapper
def __enter__(self):
pass
def __exit__(self, exc_type, exc_value, traceback):
if exc_type is None:
return
for dj_exc_type in (
DataError,
OperationalError,
IntegrityError,
InternalError,
ProgrammingError,
NotSupportedError,
DatabaseError,
InterfaceError,
Error,
):
db_exc_type = getattr(self.wrapper.Database, dj_exc_type.__name__)
if issubclass(exc_type, db_exc_type):
dj_exc_value = dj_exc_type(*exc_value.args)
# Only set the 'errors_occurred' flag for errors that may make
# the connection unusable.
if dj_exc_type not in (DataError, IntegrityError):
self.wrapper.errors_occurred = True
raise dj_exc_value.with_traceback(traceback) from exc_value
def __call__(self, func):
# Note that we are intentionally not using @wraps here for performance
# reasons. Refs #21109.
def inner(*args, **kwargs):
with self:
return func(*args, **kwargs)
return inner
def load_backend(backend_name):
"""
Return a database backend's "base" module given a fully qualified database
backend name, or raise an error if it doesn't exist.
"""
# This backend was renamed in Django 1.9.
if backend_name == "django.db.backends.postgresql_psycopg2":
backend_name = "django.db.backends.postgresql"
try:
return import_module("%s.base" % backend_name)
except ImportError as e_user:
# The database backend wasn't found. Display a helpful error message
# listing all built-in database backends.
import django.db.backends
builtin_backends = [
name
for _, name, ispkg in pkgutil.iter_modules(django.db.backends.__path__)
if ispkg and name not in {"base", "dummy"}
]
if backend_name not in ["django.db.backends.%s" % b for b in builtin_backends]:
backend_reprs = map(repr, sorted(builtin_backends))
raise ImproperlyConfigured(
"%r isn't an available database backend or couldn't be "
"imported. Check the above exception. To use one of the "
"built-in backends, use 'django.db.backends.XXX', where XXX "
"is one of:\n"
" %s" % (backend_name, ", ".join(backend_reprs))
) from e_user
else:
# If there's some other error, this must be an error in Django
raise
class ConnectionHandler(BaseConnectionHandler):
settings_name = "DATABASES"
# Connections needs to still be an actual thread local, as it's truly
# thread-critical. Database backends should use @async_unsafe to protect
# their code from async contexts, but this will give those contexts
# separate connections in case it's needed as well. There's no cleanup
# after async contexts, though, so we don't allow that if we can help it.
thread_critical = True
def configure_settings(self, databases):
databases = super().configure_settings(databases)
if databases == {}:
databases[DEFAULT_DB_ALIAS] = {"ENGINE": "django.db.backends.dummy"}
elif DEFAULT_DB_ALIAS not in databases:
raise ImproperlyConfigured(
f"You must define a '{DEFAULT_DB_ALIAS}' database."
)
elif databases[DEFAULT_DB_ALIAS] == {}:
databases[DEFAULT_DB_ALIAS]["ENGINE"] = "django.db.backends.dummy"
# Configure default settings.
for conn in databases.values():
conn.setdefault("ATOMIC_REQUESTS", False)
conn.setdefault("AUTOCOMMIT", True)
conn.setdefault("ENGINE", "django.db.backends.dummy")
if conn["ENGINE"] == "django.db.backends." or not conn["ENGINE"]:
conn["ENGINE"] = "django.db.backends.dummy"
conn.setdefault("CONN_MAX_AGE", 0)
conn.setdefault("CONN_HEALTH_CHECKS", False)
conn.setdefault("OPTIONS", {})
conn.setdefault("TIME_ZONE", None)
for setting in ["NAME", "USER", "PASSWORD", "HOST", "PORT"]:
conn.setdefault(setting, "")
test_settings = conn.setdefault("TEST", {})
default_test_settings = [
("CHARSET", None),
("COLLATION", None),
("MIGRATE", True),
("MIRROR", None),
("NAME", None),
]
for key, value in default_test_settings:
test_settings.setdefault(key, value)
return databases
@property
def databases(self):
# Maintained for backward compatibility as some 3rd party packages have
# made use of this private API in the past. It is no longer used within
# Django itself.
return self.settings
def create_connection(self, alias):
db = self.settings[alias]
backend = load_backend(db["ENGINE"])
return backend.DatabaseWrapper(db, alias)
class ConnectionRouter:
def __init__(self, routers=None):
"""
If routers is not specified, default to settings.DATABASE_ROUTERS.
"""
self._routers = routers
@cached_property
def routers(self):
if self._routers is None:
self._routers = settings.DATABASE_ROUTERS
routers = []
for r in self._routers:
if isinstance(r, str):
router = import_string(r)()
else:
router = r
routers.append(router)
return routers
def _router_func(action):
def _route_db(self, model, **hints):
chosen_db = None
for router in self.routers:
try:
method = getattr(router, action)
except AttributeError:
# If the router doesn't have a method, skip to the next one.
pass
else:
chosen_db = method(model, **hints)
if chosen_db:
return chosen_db
instance = hints.get("instance")
if instance is not None and instance._state.db:
return instance._state.db
return DEFAULT_DB_ALIAS
return _route_db
db_for_read = _router_func("db_for_read")
db_for_write = _router_func("db_for_write")
def allow_relation(self, obj1, obj2, **hints):
for router in self.routers:
try:
method = router.allow_relation
except AttributeError:
# If the router doesn't have a method, skip to the next one.
pass
else:
allow = method(obj1, obj2, **hints)
if allow is not None:
return allow
return obj1._state.db == obj2._state.db
def allow_migrate(self, db, app_label, **hints):
for router in self.routers:
try:
method = router.allow_migrate
except AttributeError:
# If the router doesn't have a method, skip to the next one.
continue
allow = method(db, app_label, **hints)
if allow is not None:
return allow
return True
def allow_migrate_model(self, db, model):
return self.allow_migrate(
db,
model._meta.app_label,
model_name=model._meta.model_name,
model=model,
)
def get_migratable_models(self, app_config, db, include_auto_created=False):
"""Return app models allowed to be migrated on provided db."""
models = app_config.get_models(include_auto_created=include_auto_created)
return [model for model in models if self.allow_migrate_model(db, model)]
