Source code for django.db.utils
import os
import pkgutil
from importlib import import_module
from threading import local
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
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.
backend_dir = os.path.join(os.path.dirname(__file__), 'backends')
builtin_backends = [
name for _, name, ispkg in pkgutil.iter_modules([backend_dir])
if ispkg and name not in {'base', 'dummy', 'postgresql_psycopg2'}
]
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.\n"
"Try using '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 ConnectionDoesNotExist(Exception):
pass
class ConnectionHandler:
def __init__(self, databases=None):
"""
databases is an optional dictionary of database definitions (structured
like settings.DATABASES).
"""
self._databases = databases
self._connections = local()
@cached_property
def databases(self):
if self._databases is None:
self._databases = settings.DATABASES
if self._databases == {}:
self._databases = {
DEFAULT_DB_ALIAS: {
'ENGINE': 'django.db.backends.dummy',
},
}
if self._databases[DEFAULT_DB_ALIAS] == {}:
self._databases[DEFAULT_DB_ALIAS]['ENGINE'] = 'django.db.backends.dummy'
if DEFAULT_DB_ALIAS not in self._databases:
raise ImproperlyConfigured("You must define a '%s' database" % DEFAULT_DB_ALIAS)
return self._databases
def ensure_defaults(self, alias):
"""
Put the defaults into the settings dictionary for a given connection
where no settings is provided.
"""
try:
conn = self.databases[alias]
except KeyError:
raise ConnectionDoesNotExist("The connection %s doesn't exist" % alias)
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('OPTIONS', {})
conn.setdefault('TIME_ZONE', None)
for setting in ['NAME', 'USER', 'PASSWORD', 'HOST', 'PORT']:
conn.setdefault(setting, '')
def prepare_test_settings(self, alias):
"""
Make sure the test settings are available in the 'TEST' sub-dictionary.
"""
try:
conn = self.databases[alias]
except KeyError:
raise ConnectionDoesNotExist("The connection %s doesn't exist" % alias)
test_settings = conn.setdefault('TEST', {})
for key in ['CHARSET', 'COLLATION', 'NAME', 'MIRROR']:
test_settings.setdefault(key, None)
def __getitem__(self, alias):
if hasattr(self._connections, alias):
return getattr(self._connections, alias)
self.ensure_defaults(alias)
self.prepare_test_settings(alias)
db = self.databases[alias]
backend = load_backend(db['ENGINE'])
conn = backend.DatabaseWrapper(db, alias)
setattr(self._connections, alias, conn)
return conn
def __setitem__(self, key, value):
setattr(self._connections, key, value)
def __delitem__(self, key):
delattr(self._connections, key)
def __iter__(self):
return iter(self.databases)
def all(self):
return [self[alias] for alias in self]
def close_all(self):
for alias in self:
try:
connection = getattr(self._connections, alias)
except AttributeError:
continue
connection.close()
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)]
