[soc2009/multidb] Fixed a problem with m2m descriptors not sticking to the right database. Patch from Russell Keith-Magee.

git-svn-id: http://code.djangoproject.com/svn/django/branches/soc2009/multidb@11873 bcc190cf-cafb-0310-a4f2-bffc1f526a37

TODO

@@ -5,6 +5,9 @@ Required for v1.2
 ~~~~~~~~~~~~~~~~~
 
  * Modify the admin interface to support multiple databases (doh).
+    - Document how it is done
+    - Modify m2m widgets to stick to the same database as parent
+    - Modify inlines to stick to same database as parent
 
 Optional for v1.2
 ~~~~~~~~~~~~~~~~~

django/db/models/fields/related.py

@@ -439,7 +439,7 @@ def create_many_related_manager(superclass, rel=False):
                 raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % instance.__class__.__name__)
 
         def get_query_set(self):
-            return superclass.get_query_set(self)._next_is_sticky().filter(**(self.core_filters))
+            return superclass.get_query_set(self).using(self.instance._state.db)._next_is_sticky().filter(**(self.core_filters))
 
         # If the ManyToMany relation has an intermediary model,
         # the add and remove methods do not exist.
@@ -1032,7 +1032,10 @@ class ManyToManyField(RelatedField, Field):
         setattr(instance, self.attname, data)
 
     def formfield(self, **kwargs):
-        defaults = {'form_class': forms.ModelMultipleChoiceField, 'queryset': self.rel.to._default_manager.complex_filter(self.rel.limit_choices_to)}
+        defaults = {
+            'form_class': forms.ModelMultipleChoiceField,
+            'queryset': self.rel.to._default_manager.complex_filter(self.rel.limit_choices_to)
+        }
         defaults.update(kwargs)
         # If initial is passed in, it's a list of related objects, but the
         # MultipleChoiceField takes a list of IDs.

tests/regressiontests/multiple_database/tests.py

@@ -160,6 +160,17 @@ class QueryTestCase(TestCase):
         self.assertEquals(list(Book.objects.using('other').filter(authors__name='Mark Pilgrim').values_list('title', flat=True)),
                           [u'Dive into Python'])
 
+        # Reget the objects to clear caches
+        dive = Book.objects.using('other').get(title="Dive into Python")
+        mark = Author.objects.using('other').get(name="Mark Pilgrim")
+
+        # Retrive related object by descriptor. Related objects should be database-baound
+        self.assertEquals(list(dive.authors.all().values_list('name', flat=True)),
+                          [u'Mark Pilgrim'])
+
+        self.assertEquals(list(mark.book_set.all().values_list('title', flat=True)),
+                          [u'Dive into Python'])
+
     def test_m2m_forward_operations(self):
         "M2M forward manipulations are all constrained to a single DB"
         # Create a book and author on the other database
@@ -286,6 +297,16 @@ class QueryTestCase(TestCase):
         self.assertEquals(list(Book.objects.using('other').filter(favourite_of__name='Mark Pilgrim').values_list('title', flat=True)),
                           [u'Dive into Python'])
 
+        # Reget the objects to clear caches
+        dive = Book.objects.using('other').get(title="Dive into Python")
+        mark = Author.objects.using('other').get(name="Mark Pilgrim")
+
+        # Retrive related object by descriptor. Related objects should be database-baound
+        self.assertEquals(list(dive.favourite_of.all().values_list('name', flat=True)),
+                          [u'Mark Pilgrim'])
+
+        self.assertEquals(mark.favourite_book.title, u'Dive into Python')
+
     def test_foreign_key_reverse_operations(self):
         "FK reverse manipulations are all constrained to a single DB"
         dive = Book.objects.using('other').create(title="Dive into Python",