+
−import os
+
−from django.conf import settings
+
−from django.core import signals
+
−from django.core.exceptions import ImproperlyConfigured
+
−from django.utils.functional import curry
+
−
+
−__all__ = ('backend', 'connection', 'DatabaseError', 'IntegrityError')
+
−
+
−if not settings.DATABASE_ENGINE:
+
−    settings.DATABASE_ENGINE = 'dummy'
+
−
+
−try:
+
−    # Most of the time, the database backend will be one of the official
+
−    # backends that ships with Django, so look there first.
+
−    _import_path = 'django.db.backends.'
+
−    backend = __import__('%s%s.base' % (_import_path, settings.DATABASE_ENGINE), {}, {}, [''])
+
−except ImportError, e:
+
−    # If the import failed, we might be looking for a database backend
+
−    # distributed external to Django. So we'll try that next.
+
−    try:
+
−        _import_path = ''
+
−        backend = __import__('%s.base' % settings.DATABASE_ENGINE, {}, {}, [''])
+
−    except ImportError, e_user:
+
−        # The database backend wasn't found. Display a helpful error message
+
−        # listing all possible (built-in) database backends.
+
−        backend_dir = os.path.join(__path__[0], 'backends')
+
−        try:
+
−            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')]
+
−        except EnvironmentError:
+
−            available_backends = []
+
−        available_backends.sort()
+
−        if settings.DATABASE_ENGINE not in available_backends:
+
−            raise ImproperlyConfigured, "%r isn't an available database backend. Available options are: %s\nError was: %s" % \
+
−                (settings.DATABASE_ENGINE, ", ".join(map(repr, available_backends)), e_user)
+
−        else:
+
−            raise # If there's some other error, this must be an error in Django itself.
+
−
+
−# Convenient aliases for backend bits.
+
−connection = backend.DatabaseWrapper(**settings.DATABASE_OPTIONS)
+
−DatabaseError = backend.DatabaseError
+
−IntegrityError = backend.IntegrityError
+
−
+
−# Register an event that closes the database connection
+
−# when a Django request is finished.
+
−def close_connection(**kwargs):
+
−    connection.close()
+
−signals.request_finished.connect(close_connection)
+
−
+
−# Register an event that resets connection.queries
+
−# when a Django request is started.
+
−def reset_queries(**kwargs):
+
−    connection.queries = []
+
−signals.request_started.connect(reset_queries)
+
−
+
−# Register an event that rolls back the connection
+
−# when a Django request has an exception.
+
−def _rollback_on_exception(**kwargs):
+
−    from django.db import transaction
+
−    try:
+
−        transaction.rollback_unless_managed()
+
−    except DatabaseError:
+
−        pass
+
−signals.got_request_exception.connect(_rollback_on_exception)