selectin polymorphic loading

Added a new style of mapper-level inheritance loading
"polymorphic selectin".  This style of loading
emits queries for each subclass in an inheritance
hierarchy subsequent to the load of the base
object type, using IN to specify the desired
primary key values.

Fixes: #3948

Change-Id: I59e071c6142354a3f95730046e3dcdfc0e2c4de5

1 files changed, 7 insertions, 4 deletions

diff --git a/lib/sqlalchemy/ext/baked.py b/lib/sqlalchemy/ext/baked.py
index ba3c2aed0..c0fe963ac 100644
--- a/lib/sqlalchemy/ext/baked.py
+++ b/lib/sqlalchemy/ext/baked.py
@@ -154,7 +154,7 @@ class BakedQuery(object):
         self._spoiled = True
         return self
 
-    def _add_lazyload_options(self, options, effective_path):
+    def _add_lazyload_options(self, options, effective_path, cache_path=None):
         """Used by per-state lazy loaders to add options to the
         "lazy load" query from a parent query.
 
@@ -166,13 +166,16 @@ class BakedQuery(object):
 
         key = ()
 
-        if effective_path.path[0].is_aliased_class:
+        if not cache_path:
+            cache_path = effective_path
+
+        if cache_path.path[0].is_aliased_class:
             # paths that are against an AliasedClass are unsafe to cache
             # with since the AliasedClass is an ad-hoc object.
             self.spoil()
         else:
             for opt in options:
-                cache_key = opt._generate_cache_key(effective_path)
+                cache_key = opt._generate_cache_key(cache_path)
                 if cache_key is False:
                     self.spoil()
                 elif cache_key is not None:
@@ -181,7 +184,7 @@ class BakedQuery(object):
         self.add_criteria(
             lambda q: q._with_current_path(effective_path).
             _conditional_options(*options),
-            effective_path.path, key
+            cache_path.path, key
         )
 
     def _retrieve_baked_query(self, session):