Use baked lazyloading by default

The ``lazy="select"`` loader strategy now makes used of the
:class:`.BakedQuery` query caching system in all cases.  This
removes most overhead of generating a :class:`.Query` object and
running it into a :func:`.select` and then string SQL statement from
the process of lazy-loading related collections and objects.  The
"baked" lazy loader has also been improved such that it can now
cache in most cases where query load options are used.

Change-Id: Ic96792fffaa045ae9aa0a4657d6d29235d3efb85
Fixes: #3954

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index 73b0be99c..2e61661ed 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -1039,6 +1039,19 @@ def was_deleted(object):
     state = attributes.instance_state(object)
     return state.was_deleted
 
+def _entity_corresponds_to(given, entity):
+    if entity.is_aliased_class:
+        if given.is_aliased_class:
+            if entity._base_alias is given._base_alias:
+                return True
+        return False
+    elif given.is_aliased_class:
+        if given._use_mapper_path:
+            return entity in given.with_polymorphic_mappers
+        else:
+            return entity is given
+
+    return entity.common_parent(given)
 
 def randomize_unitofwork():
     """Use random-ordering sets within the unit of work in order