Fixed #13227 -- Modified ForeignKeys to fully honor the db_prep/prep separation introduced by multidb. This was required to ensure that model instances aren't deepcopied as a result of being involved in a filter clause. Thanks to claudep for the report, and Alex Gaynor for the help on the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12865 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query_utils.py

@@ -155,7 +155,8 @@ class Q(tree.Node):
     def _combine(self, other, conn):
         if not isinstance(other, Q):
             raise TypeError(other)
-        obj = deepcopy(self)
+        obj = type(self)()
+        obj.add(self, conn)
         obj.add(other, conn)
         return obj
 
@@ -166,7 +167,8 @@ class Q(tree.Node):
         return self._combine(other, self.AND)
 
     def __invert__(self):
-        obj = deepcopy(self)
+        obj = type(self)()
+        obj.add(self, self.AND)
         obj.negate()
         return obj