Merge branch 'master' into ticket_3100

diff --cc lib/sqlalchemy/orm/mapper.py
index b98fbda42069a8255435c35f479ecfb3e02de98a,f22cac329cead928be0d078862f396132235a345..63d23e31d1c538877cad8fb7abc45db1ec921619
--- 1/lib/sqlalchemy/orm/mapper.py
--- 2/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@@ -2364,12 -2364,11 +2364,15 @@@ class Mapper(InspectionAttr)
  
      @_memoized_configured_property
      def _primary_key_props(self):
+         # TODO: this should really be called "identity key props",
+         # as it does not necessarily include primary key columns within
+         # individual tables
          return [self._columntoproperty[col] for col in self.primary_key]
  
 +    @_memoized_configured_property
 +    def _primary_key_propkeys(self):
 +        return set([prop.key for prop in self._primary_key_props])
 +
      def _get_state_attr_by_column(
              self, state, dict_, column,
              passive=attributes.PASSIVE_RETURN_NEVER_SET):

diff --cc lib/sqlalchemy/orm/persistence.py
Simple merge