django1/django/db/__init__.py

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from django.conf import settings
from django.core import signals
from django.core.exceptions import ImproperlyConfigured
from django.db.utils import (ConnectionHandler, ConnectionRouter,
load_backend, DEFAULT_DB_ALIAS, DatabaseError, IntegrityError)
__all__ = ('backend', 'connection', 'connections', 'router', 'DatabaseError',
'IntegrityError', 'DEFAULT_DB_ALIAS')
if settings.DATABASES and DEFAULT_DB_ALIAS not in settings.DATABASES:
raise ImproperlyConfigured("You must define a '%s' database" % DEFAULT_DB_ALIAS)
connections = ConnectionHandler(settings.DATABASES)
router = ConnectionRouter(settings.DATABASE_ROUTERS)
# `connection`, `DatabaseError` and `IntegrityError` are convenient aliases
# for backend bits.
# DatabaseWrapper.__init__() takes a dictionary, not a settings module, so
# we manually create the dictionary from the settings, passing only the
# settings that the database backends care about. Note that TIME_ZONE is used
# by the PostgreSQL backends.
# We load all these up for backwards compatibility, you should use
# connections['default'] instead.
class DefaultConnectionProxy(object):
"""
Proxy for accessing the default DatabaseWrapper object's attributes. If you
need to access the DatabaseWrapper object itself, use
connections[DEFAULT_DB_ALIAS] instead.
"""
def __getattr__(self, item):
return getattr(connections[DEFAULT_DB_ALIAS], item)
def __setattr__(self, name, value):
return setattr(connections[DEFAULT_DB_ALIAS], name, value)
connection = DefaultConnectionProxy()
backend = load_backend(connection.settings_dict['ENGINE'])
# Register an event that closes the database connection
# when a Django request is finished.
def close_connection(**kwargs):
# Avoid circular imports
from django.db import transaction
for conn in connections:
# If an error happens here the connection will be left in broken
# state. Once a good db connection is again available, the
# connection state will be cleaned up.
transaction.abort(conn)
connections[conn].close()
signals.request_finished.connect(close_connection)
# Register an event that resets connection.queries
# when a Django request is started.
def reset_queries(**kwargs):
for conn in connections.all():
conn.queries = []
signals.request_started.connect(reset_queries)
# Register an event that rolls back the connections
# when a Django request has an exception.
def _rollback_on_exception(**kwargs):
from django.db import transaction
for conn in connections:
try:
transaction.rollback_unless_managed(using=conn)
except DatabaseError:
pass
signals.got_request_exception.connect(_rollback_on_exception)