- merged instances_yields branch r3908:3934, minus the "yield" part which remains slightly problematic

- cleanup of mapper._instance, query.instances().  mapper identifies objects which are part of the
current load using a app-unique id on the query context.
- attributes refactor; attributes now mostly use copy-on-modify instead of copy-on-load behavior,
simplified get_history(), added a new set of tests
- fixes to OrderedSet such that difference(), intersection() and others can accept an iterator
- OrderedIdentitySet passes in OrderedSet to the IdentitySet superclass for usage in difference/intersection/etc. operations so that these methods actually work with ordering behavior.
- query.order_by() takes into account aliased joins, i.e.  query.join('orders', aliased=True).order_by(Order.id)
- cleanup etc.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 413a1af2c..6119d1c6e 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -383,7 +383,7 @@ class MapperProperty(object):
         level (as opposed to the individual instance level).
         """
 
-        return self.parent._is_primary_mapper()
+        return not self.parent.non_primary
 
     def merge(self, session, source, dest):
         """Merge the attribute represented by this ``MapperProperty``