1 import os

     2 from django.conf import settings

     3 from django.core import signals

     4 from django.core.exceptions import ImproperlyConfigured

     5 from django.utils.functional import curry

     6 from django.utils.importlib import import_module

     7 

     8 __all__ = ('backend', 'connection', 'DatabaseError', 'IntegrityError')

     9 

    10 if not settings.DATABASE_ENGINE:

    11     settings.DATABASE_ENGINE = 'dummy'

    12 

    13 def load_backend(backend_name):

    14     try:

    15         # Most of the time, the database backend will be one of the official

    16         # backends that ships with Django, so look there first.

    17         return import_module('.base', 'django.db.backends.%s' % backend_name)

    18     except ImportError, e:

    19         # If the import failed, we might be looking for a database backend

    20         # distributed external to Django. So we'll try that next.

    21         try:

    22             return import_module('.base', backend_name)

    23         except ImportError, e_user:

    24             # The database backend wasn't found. Display a helpful error message

    25             # listing all possible (built-in) database backends.

    26             backend_dir = os.path.join(__path__[0], 'backends')

    27             try:

    28                 available_backends = [f for f in os.listdir(backend_dir)

    29                         if os.path.isdir(os.path.join(backend_dir, f))

    30                         and not f.startswith('.')]

    31             except EnvironmentError:

    32                 available_backends = []

    33             available_backends.sort()

    34             if backend_name not in available_backends:

    35                 error_msg = "%r isn't an available database backend. Available options are: %s\nError was: %s" % \

    36                     (backend_name, ", ".join(map(repr, available_backends)), e_user)

    37                 raise ImproperlyConfigured(error_msg)

    38             else:

    39                 raise # If there's some other error, this must be an error in Django itself.

    40 

    41 backend = load_backend(settings.DATABASE_ENGINE)

    42 

    43 # `connection`, `DatabaseError` and `IntegrityError` are convenient aliases

    44 # for backend bits.

    45 

    46 # DatabaseWrapper.__init__() takes a dictionary, not a settings module, so

    47 # we manually create the dictionary from the settings, passing only the

    48 # settings that the database backends care about. Note that TIME_ZONE is used

    49 # by the PostgreSQL backends.

    50 connection = backend.DatabaseWrapper({

    51     'DATABASE_HOST': settings.DATABASE_HOST,

    52     'DATABASE_NAME': settings.DATABASE_NAME,

    53     'DATABASE_OPTIONS': settings.DATABASE_OPTIONS,

    54     'DATABASE_PASSWORD': settings.DATABASE_PASSWORD,

    55     'DATABASE_PORT': settings.DATABASE_PORT,

    56     'DATABASE_USER': settings.DATABASE_USER,

    57     'TIME_ZONE': settings.TIME_ZONE,

    58 })

    59 DatabaseError = backend.DatabaseError

    60 IntegrityError = backend.IntegrityError

    61 

    62 # Register an event that closes the database connection

    63 # when a Django request is finished.

    64 def close_connection(**kwargs):

    65     connection.close()

    66 signals.request_finished.connect(close_connection)

    67 

    68 # Register an event that resets connection.queries

    69 # when a Django request is started.

    70 def reset_queries(**kwargs):

    71     connection.queries = []

    72 signals.request_started.connect(reset_queries)

    73 

    74 # Register an event that rolls back the connection

    75 # when a Django request has an exception.

    76 def _rollback_on_exception(**kwargs):

    77     from django.db import transaction

    78     try:

    79         transaction.rollback_unless_managed()

    80     except DatabaseError:

    81         pass

    82 signals.got_request_exception.connect(_rollback_on_exception)