- a non_primary mapper will inherit the _identity_class

of the primary mapper.  This so that a non_primary
established against a class that's normally in an
inheritance mapping will produce results that are
identity-map compatible with that of the primary
mapper [ticket:2151] (also in 0.6.8)

CHANGES

@@ -31,6 +31,13 @@ CHANGES
   - horizontal shard query should use execution
     options per connection as per [ticket:2131]
 
+  - a non_primary mapper will inherit the _identity_class
+    of the primary mapper.  This so that a non_primary
+    established against a class that's normally in an
+    inheritance mapping will produce results that are 
+    identity-map compatible with that of the primary
+    mapper [ticket:2151] (also in 0.6.8)
+
 - sql
   - Some improvements to error handling inside
     of the execute procedure to ensure auto-close

lib/sqlalchemy/orm/mapper.py

@@ -589,6 +589,7 @@ class Mapper(object):
                     "a primary mapper first before setting up a non primary "
                     "Mapper." % self.class_)
             self.class_manager = manager
+            self._identity_class = manager.mapper._identity_class
             _mapper_registry[self] = True
             return
 

test/orm/test_mapper.py

@@ -474,6 +474,21 @@ class MapperTest(_fixtures.FixtureTest):
         assert n1.children[0] is n1._children[0] is n2
         eq_(str(Node.parent == n2), ":param_1 = nodes.parent_id")
 
+    def test_non_primary_identity_class(self):
+        User = self.classes.User
+        users, addresses = self.tables.users, self.tables.addresses
+        class AddressUser(User):
+            pass
+        m1 = mapper(User, users, polymorphic_identity='user')
+        m2 = mapper(AddressUser, addresses, inherits=User, 
+                        polymorphic_identity='address')
+        m3 = mapper(AddressUser, addresses, non_primary=True)
+        assert m3._identity_class is m2._identity_class
+        eq_(
+            m2.identity_key_from_instance(AddressUser()),
+            m3.identity_key_from_instance(AddressUser())
+        )
+
     def test_illegal_non_primary(self):
         users, Address, addresses, User = (self.tables.users,
                                 self.classes.Address,