Add support for multidb with Django (Closes #171).

The ``factory.django.DjangoModelFactory`` now takes an extra option:

```
class MyFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = models.MyModel
        database = 'replica'
```

This will create all instances of ``models.Model`` in the ``'replica'``
database.

6 files changed, 34 insertions, 3 deletions

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 0cf8368..c2da698 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -11,6 +11,7 @@ ChangeLog
 
     - Add support for getting/setting :mod:`factory.fuzzy`'s random state (see :issue:`175`, :issue:`185`).
     - Support lazy evaluation of iterables in :class:`factory.fuzzy.FuzzyChoice` (see :issue:`184`).
+    - Support non-default databases at the factory level (see :issue:`171`)
 
 *Bugfix:*
 
diff --git a/docs/orms.rst b/docs/orms.rst
index a0afc40..5105e66 100644
--- a/docs/orms.rst
+++ b/docs/orms.rst
@@ -42,7 +42,14 @@ All factories for a Django :class:`~django.db.models.Model` should use the
 
 .. class:: DjangoOptions(factory.base.FactoryOptions)
 
-    The ``class Meta`` on a :class:`~DjangoModelFactory` supports an extra parameter:
+    The ``class Meta`` on a :class:`~DjangoModelFactory` supports extra parameters:
+
+    .. attribute:: database
+
+        .. versionadded:: 2.5.0
+
+        All queries to the related model will be routed to the given database.
+        It defaults to ``'default'``.
 
     .. attribute:: django_get_or_create
 
diff --git a/factory/django.py b/factory/django.py
index e823ee9..ee5749a 100644
--- a/factory/django.py
+++ b/factory/django.py
@@ -56,6 +56,7 @@ class DjangoOptions(base.FactoryOptions):
     def _build_default_options(self):
         return super(DjangoOptions, self)._build_default_options() + [
             base.OptionDefault('django_get_or_create', (), inherit=True),
+            base.OptionDefault('database', 'default', inherit=True),
         ]
 
     def _get_counter_reference(self):
@@ -100,9 +101,12 @@ class DjangoModelFactory(base.Factory):
             raise base.AssociatedClassError("No model set on %s.%s.Meta"
                     % (cls.__module__, cls.__name__))
         try:
-            return model_class._default_manager   # pylint: disable=W0212
+            manager = model_class._default_manager   # pylint: disable=W0212
         except AttributeError:
-            return model_class.objects
+            manager = model_class.objects
+
+        manager = manager.using(cls._meta.database)
+        return manager
 
     @classmethod
     def _get_or_create(cls, model_class, *args, **kwargs):
diff --git a/tests/djapp/settings.py b/tests/djapp/settings.py
index c051faf..18e43dd 100644
--- a/tests/djapp/settings.py
+++ b/tests/djapp/settings.py
@@ -34,6 +34,9 @@ DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.sqlite3',
     },
+    'replica': {
+        'ENGINE': 'django.db.backends.sqlite3',
+    },
 }
 
 
diff --git a/tests/test_django.py b/tests/test_django.py
index 4653305..a8f1f77 100644
--- a/tests/test_django.py
+++ b/tests/test_django.py
@@ -165,6 +165,16 @@ class ModelTests(django_test.TestCase):
 
         self.assertRaises(factory.FactoryError, UnsetModelFactory.create)
 
+    def test_cross_database(self):
+        class OtherDBFactory(factory.django.DjangoModelFactory):
+            class Meta:
+                model = models.StandardModel
+                database = 'replica'
+
+        obj = OtherDBFactory()
+        self.assertFalse(models.StandardModel.objects.exists())
+        self.assertEqual(obj, models.StandardModel.objects.using('replica').get())
+
 
 @unittest.skipIf(django is None, "Django not installed.")
 class DjangoPkSequenceTestCase(django_test.TestCase):
diff --git a/tests/test_using.py b/tests/test_using.py
index 7318f2e..1d7977f 100644
--- a/tests/test_using.py
+++ b/tests/test_using.py
@@ -69,6 +69,9 @@ class FakeModel(object):
         def order_by(self, *args, **kwargs):
             return [1]
 
+        def using(self, db):
+            return self
+
     objects = FakeModelManager()
 
     def __init__(self, **kwargs):
@@ -1490,6 +1493,9 @@ class BetterFakeModelManager(object):
         instance.id = 2
         return instance, True
 
+    def using(self, db):
+        return self
+
 
 class BetterFakeModel(object):
     @classmethod