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[multi-db] Refactored connection handling to correct bugs in original
design relating to thread and request isolation. Changed name of optional named databases attribute in settings to settings.OTHER_DATABASES. git-svn-id: http://code.djangoproject.com/svn/django/branches/multiple-db-support@3334 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Jason Pellerin
parent
c0132e88f6
commit
97d1f60d77
@ -3,8 +3,18 @@ from django.core import signals
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from django.core.exceptions import ImproperlyConfigured
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from django.dispatch import dispatcher
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try:
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# Only exists in Python 2.4+
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from threading import local
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except ImportError:
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# Import copy of _thread_local.py from Python 2.4
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from django.utils._threading_local import local
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__all__ = ('backend', 'connection', 'DatabaseError')
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# singleton to represent the default connection in connections
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_default = object()
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if not settings.DATABASE_ENGINE:
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settings.DATABASE_ENGINE = 'dummy'
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@ -13,22 +23,7 @@ def connect(settings):
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ConnectionInfo on succes, raises ImproperlyConfigured if the
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settings don't specify a valid database connection.
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"""
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try:
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backend = __import__('django.db.backends.%s.base' % settings.DATABASE_ENGINE, '', '', [''])
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except ImportError, e:
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# The database backend wasn't found. Display a helpful error message
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# listing all possible database backends.
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import os
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backend_dir = os.path.join(__path__[0], 'backends')
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available_backends = [f for f in os.listdir(backend_dir) if not f.startswith('_') and not f.startswith('.') and not f.endswith('.py') and not f.endswith('.pyc')]
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available_backends.sort()
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if settings.DATABASE_ENGINE not in available_backends:
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raise ImproperlyConfigured, "%r isn't an available database backend. vailable options are: %s" % \
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(settings.DATABASE_ENGINE, ", ".join(map(repr, available_backends)))
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else:
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raise # If there's some other error, this must be an error in Django itself.
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info = ConnectionInfo(backend, settings)
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info = ConnectionInfo(settings)
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# Register an event that closes the database connection
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# when a Django request is finished.
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@ -47,11 +42,13 @@ class ConnectionInfo(object):
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creation, introspection, and shell modules, closing the
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connection, and resetting the connection's query log.
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"""
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def __init__(self, backend, settings):
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self.backend = backend
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def __init__(self, settings=None):
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if settings is None:
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from django.conf import settings
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self.settings = settings
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self.connection = backend.DatabaseWrapper(settings)
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self.DatabaseError = backend.DatabaseError
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self.backend = self.load_backend()
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self.connection = self.backend.DatabaseWrapper(settings)
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self.DatabaseError = self.backend.DatabaseError
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def __repr__(self):
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return "Connection: %r (ENGINE=%s NAME=%s)" \
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@ -71,6 +68,33 @@ class ConnectionInfo(object):
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return __import__('django.db.backends.%s.creation' %
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self.settings.DATABASE_ENGINE, '', '', [''])
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def load_backend(self):
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try:
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backend = __import__('django.db.backends.%s.base' %
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self.settings.DATABASE_ENGINE, '', '', [''])
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except ImportError, e:
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# The database backend wasn't found. Display a helpful error
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# message listing all possible database backends.
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import os
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backend_dir = os.path.join(__path__[0], 'backends')
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available_backends = [f for f in os.listdir(backend_dir)
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if not f.startswith('_') \
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and not f.startswith('.') \
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and not f.endswith('.py') \
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and not f.endswith('.pyc')]
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available_backends.sort()
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if settings.DATABASE_ENGINE not in available_backends:
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raise ImproperlyConfigured, \
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"%r isn't an available database backend. "\
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"Available options are: %s" % \
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(settings.DATABASE_ENGINE,
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", ".join(map(repr, available_backends)))
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else:
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# If there's some other error, this must be an error
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# in Django itself.
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raise
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return backend
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def runshell(self):
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__import__('django.db.backends.%s.client' %
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self.settings.DATABASE_ENGINE, '', '', ['']).runshell()
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@ -79,70 +103,161 @@ class ConnectionInfo(object):
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"""Reset log of queries executed by connection"""
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self.connection.queries = []
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class LazyConnectionManager(object):
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"""Manages named connections lazily, instantiating them as
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they are requested.
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"""
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def __init__(self):
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self._connections = {}
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self.local = local()
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self.local.connections = {}
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def __iter__(self):
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return self._connections.keys()
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return self.local.connections.keys()
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def __getattr__(self, attr):
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# use __dict__ to avoid getattr() loop
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return getattr(self.__dict__['_connections'], attr)
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return getattr(self.local.connections, attr)
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def __getitem__(self, k):
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try:
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return self.__dict__['_connections'][k]
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return self.local.connections[k]
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except KeyError:
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return self.connect(k)
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def __setitem__(self, k, v):
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self.__dict__['_connections'][k] = v
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self.local.connections[k] = v
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def connect(self, name):
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"""Return the connection with this name in
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settings.DATABASES. Creates the connection if it doesn't yet
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exist. Reconnects if it does.
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settings.OTHER_DATABASES. Creates the connection if it doesn't yet
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exist. Reconnects if it does. If the name requested is the default
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connection (a singleton defined in django.db), then the default
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connection is returned.
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"""
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if name in self._connections:
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self._connections[name].close()
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cnx = self.local.connections
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if name in cnx:
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cnx[name].close()
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if name is _default:
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# get the default connection from connection_info
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if connection_info.local.db is None:
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connection_info.init_connection()
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cnx[name] = connection_info.local.db
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return cnx[name]
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try:
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info = settings.DATABASES[name]
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info = settings.OTHER_DATABASES[name]
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except KeyError:
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raise ImproperlyConfigured, \
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"No database connection '%s' has been configured" % name
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except AttributeError:
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raise ImproperlyConfigured, \
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"No DATABASES in settings."
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"No OTHER_DATABASES in settings."
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# In settings it's a dict, but connect() needs an object
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# In settings it's a dict, but connect() needs an object:
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# pass global settings so that the default connection settings
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# can be defaults for the named connections
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# can be defaults for the named connections.
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database = UserSettingsHolder(settings)
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for k, v in info.items():
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setattr(database, k, v)
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self._connections[name] = connect(database)
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return self._connections[name]
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cnx[name] = connect(database)
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return cnx[name]
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def reset(self):
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self.local.connections = {}
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class _proxy:
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"""A lazy-initializing proxy. The proxied object is not
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initialized until the first attempt to access it.
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"""
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def __init__(self, init_obj):
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self.__dict__['_obj'] = None
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self.__dict__['_init_obj'] = init_obj
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def __getattr__(self, attr):
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if self.__dict__['_obj'] is None:
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self.__dict__['_obj'] = self.__dict__['_init_obj']()
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return getattr(self.__dict__['_obj'], attr)
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def __setattr__(self, attr, val):
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if self.__dict__['_obj'] is None:
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self.__dict__['_obj'] = self.__dict__['_init_obj']()
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setattr(self.__dict__['_obj'], attr, val)
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class DefaultConnectionInfoProxy(object):
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"""Holder for proxy objects that will connect to the current
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default connection when used. Mimics the interface of a ConnectionInfo.
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"""
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def __init__(self):
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self.local = local()
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self.local.db = None
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self.connection = _proxy(self.get_connection)
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self.DatabaseError = _proxy(self.get_database_error)
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self.backend = _proxy(self.get_backend)
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self.get_introspection_module = _proxy(self.get_introspection_module)
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self.get_creation_module = _proxy(self.get_creation_module)
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self.runshell = _proxy(self.get_runshell)
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def init_connection(self):
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from django.conf import settings
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self.local.db = connect(settings)
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def get_backend(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.backend
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def get_connection(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.connection
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def get_database_error(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.DatabaseError
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def get_introspection_module(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.get_introspection_module
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def get_creation_module(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.get_creation_module
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def get_runshell(self):
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if self.local.db is None:
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self.init_connection()
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return self.local.db.runshell
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def close(self):
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self.local.db = None
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# Backwards compatibility: establish the default connection and set the
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# default connection properties at module level
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connection_info = connect(settings)
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connection_info = DefaultConnectionInfoProxy()
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(connection, DatabaseError, backend, get_introspection_module,
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get_creation_module, runshell) = (connection_info.connection,
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connection_info.DatabaseError,
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connection_info.backend,
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connection_info.get_introspection_module,
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connection_info.get_introspection_module,
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connection_info.get_creation_module,
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connection_info.runshell)
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# Create a manager for named connections
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connections = LazyConnectionManager()
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# Reset connections on request finish, to make sure each request can
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# load the correct connections for its settings
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dispatcher.connect(connections.reset, signal=signals.request_finished)
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# Clear the default connection on request finish also
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dispatcher.connect(connection_info.close, signal=signals.request_finished)
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# Register an event that rolls back all connections
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# when a Django request has an exception.
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def _rollback_on_exception():
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