- Fixed bug whereby calling query(A).join(A.bs).add_entity(B)

in a joined inheritance scenario would double-add B as a
target and produce an invalid query.  [ticket:1188]

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 682aa2bbf..8d3d7fbb3 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -114,7 +114,8 @@ class Query(object):
                     mapper, selectable, is_aliased_class = _entity_info(entity)
                     if not is_aliased_class and mapper.with_polymorphic:
                         with_polymorphic = mapper._with_polymorphic_mappers
-                        self.__mapper_loads_polymorphically_with(mapper, 
+                        if mapper.mapped_table not in self._polymorphic_adapters:
+                            self.__mapper_loads_polymorphically_with(mapper, 
                                 sql_util.ColumnAdapter(selectable, mapper._equivalent_columns))
                         adapter = None
                     elif is_aliased_class: