magic-removal: Fixed #1143 -- Fixed backwards incompatibilities in many-to-many DB API lookups, added support for reverse many-to-many lookups, added unit tests. Thanks, Russ

git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@1802 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -236,10 +236,11 @@ def parse_lookup(kwarg_items, opts):
                     # is set to True, which means the kwarg was bad.
                     # Example: choices.get_list(poll__exact='foo')
                     throw_bad_kwarg_error(kwarg)
-                # Try many-to-many relationships first...
+                # Try many-to-many relationships in the direction in which they are
+                # originally defined (i.e., the class that defines the ManyToManyField)
                 for f in current_opts.many_to_many:
                     if f.name == current:
-                        rel_table_alias = backend.quote_name(current_table_alias + LOOKUP_SEPARATOR + current)
+                        rel_table_alias = backend.quote_name("m2m_" + current_table_alias + LOOKUP_SEPARATOR + current)
 
                         joins[rel_table_alias] = (
                             backend.quote_name(f.get_m2m_db_table(current_opts)),
@@ -275,6 +276,46 @@ def parse_lookup(kwarg_items, opts):
                             param_required = True
                         current_opts = f.rel.to._meta
                         raise StopIteration
+                # Try many-to-many relationships first in the reverse direction
+                # (i.e., from the class does not have the ManyToManyField)
+                for f in current_opts.get_all_related_many_to_many_objects():
+                    if f.name == current:
+                        rel_table_alias = backend.quote_name("m2m_" + current_table_alias + LOOKUP_SEPARATOR + current)
+
+                        joins[rel_table_alias] = (
+                            backend.quote_name(f.field.get_m2m_db_table(f.opts)),
+                            "INNER JOIN",
+                            '%s.%s = %s.%s' %
+                                (backend.quote_name(current_table_alias),
+                                backend.quote_name(current_opts.pk.column),
+                                rel_table_alias,
+                                backend.quote_name(current_opts.object_name.lower() + '_id'))
+                        )
+
+                        # Optimization: In the case of primary-key lookups, we
+                        # don't have to do an extra join.
+                        if lookup_list and lookup_list[0] == f.opts.pk.name and lookup_type == 'exact':
+                            where.append(get_where_clause(lookup_type, rel_table_alias+'.',
+                                f.opts.object_name.lower()+'_id', kwarg_value))
+                            params.extend(f.field.get_db_prep_lookup(lookup_type, kwarg_value))
+                            lookup_list.pop()
+                            param_required = False
+                        else:
+                            new_table_alias = current_table_alias + LOOKUP_SEPARATOR + current
+
+                            joins[backend.quote_name(new_table_alias)] = (
+                                backend.quote_name(f.opts.db_table),
+                                "INNER JOIN",
+                                '%s.%s = %s.%s' %
+                                    (rel_table_alias,
+                                    backend.quote_name(f.opts.object_name.lower() + '_id'),
+                                    backend.quote_name(new_table_alias),
+                                    backend.quote_name(f.opts.pk.column))
+                            )
+                            current_table_alias = new_table_alias
+                            param_required = True
+                        current_opts = f.opts
+                        raise StopIteration
                 for f in current_opts.fields:
                     # Try many-to-one relationships...
                     if f.rel and f.name == current:

tests/modeltests/many_to_many/models.py

@@ -28,6 +28,8 @@ API_TESTS = """
 >>> p1.save()
 >>> p2 = Publication(id=None, title='Science News')
 >>> p2.save()
+>>> p3 = Publication(id=None, title='Science Weekly')
+>>> p3.save()
 
 # Create an Article.
 >>> a1 = Article(id=None, headline='Django lets you build Web apps easily')
@@ -50,14 +52,14 @@ False
 True
 >>> a2.set_publications([p1.id])
 True
->>> a2.set_publications([p1.id, p2.id])
+>>> a2.set_publications([p1.id, p2.id, p3.id])
 True
 
 # Article objects have access to their related Publication objects.
 >>> a1.get_publication_list()
 [The Python Journal]
 >>> a2.get_publication_list()
-[The Python Journal, Science News]
+[The Python Journal, Science News, Science Weekly]
 
 # Publication objects have access to their related Article objects.
 >>> p2.get_article_list()
@@ -65,10 +67,27 @@ True
 >>> p1.get_article_list(order_by=['headline'])
 [Django lets you build Web apps easily, NASA uses Python]
 
+# We can perform kwarg queries across m2m relationships
+>>> Article.objects.get_list(publications__pk=1)
+[Django lets you build Web apps easily, NASA uses Python]
+
+>>> Article.objects.get_list(publications__title__startswith="Science")
+[NASA uses Python, NASA uses Python]
+
+>>> Article.objects.get_list(publications__title__startswith="Science", distinct=True)
+[NASA uses Python]
+
+# Reverse m2m queries (i.e., start at the table that doesn't have a ManyToManyField)
+>>> Publication.objects.get_list(articles__headline__startswith="NASA")
+[The Python Journal, Science News, Science Weekly]
+
+>>> Publication.objects.get_list(articles__pk=1)
+[The Python Journal]
+
 # If we delete a Publication, its Articles won't be able to access it.
 >>> p1.delete()
 >>> Publication.objects.get_list()
-[Science News]
+[Science News, Science Weekly]
 >>> a1 = Article.objects.get_object(pk=1)
 >>> a1.get_publication_list()
 []

tests/modeltests/one_to_one/models.py

@@ -66,6 +66,8 @@ DoesNotExist: Restaurant does not exist for {'place__id__exact': ...}
 
 >>> Restaurant.objects.get_object(place__id__exact=1)
 Demon Dogs the restaurant
+>>> Restaurant.objects.get_object(place__name__startswith="Demon")
+Demon Dogs the restaurant
 >>> Restaurant.objects.get_object(pk=1)
 Demon Dogs the restaurant