- reworked the internals of mapper.cascade_iterator() to

cut down method calls by about 9% in some circumstances.
[ticket:1932]

3 files changed, 35 insertions, 17 deletions

diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 0a65c8a44..fa27859ec 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -76,7 +76,7 @@ class MapperExtension(object):
     mapper activity will not be performed.
     
     """
-
+    
     def instrument_class(self, mapper, class_):
         """Receive a class when the mapper is first constructed, and has
         applied instrumentation to the mapped class.
@@ -418,6 +418,13 @@ class MapperProperty(object):
     attribute access, loading behavior, and dependency calculations.
     """
 
+    cascade = ()
+    """The set of 'cascade' attribute names.
+    
+    This collection is checked before the 'cascade_iterator' method is called.
+    
+    """
+
     def setup(self, context, entity, path, adapter, **kwargs):
         """Called by Query for the purposes of constructing a SQL statement.
 
@@ -469,6 +476,11 @@ class MapperProperty(object):
                             halt_on=None):
         """Iterate through instances related to the given instance for
         a particular 'cascade', starting with this MapperProperty.
+        
+        Return an iterator3-tuples (instance, mapper, state).
+        
+        Note that the 'cascade' collection on this MapperProperty is
+        checked first for the given type before cascade_iterator is called.
 
         See PropertyLoader for the related instance implementation.
         """
diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 49f5d2190..d27b99601 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -1401,25 +1401,30 @@ class Mapper(object):
 
         """
         visited_instances = util.IdentitySet()
-        visitables = [(self._props.itervalues(), 'property', state)]
+        prp, mpp = object(), object()
+
+        visitables = [(deque(self._props.values()), prp, state)]
 
         while visitables:
             iterator, item_type, parent_state = visitables[-1]
-            try:
-                if item_type == 'property':
-                    prop = iterator.next()
-                    visitables.append(
-                                (prop.cascade_iterator(type_, parent_state, 
-                                visited_instances, halt_on), 'mapper', None)
-                                )
-                elif item_type == 'mapper':
-                    instance, instance_mapper, corresponding_state  = \
-                                    iterator.next()
-                    yield (instance, instance_mapper)
-                    visitables.append((instance_mapper._props.itervalues(), 
-                                            'property', corresponding_state))
-            except StopIteration:
+            if not iterator:
                 visitables.pop()
+                continue
+                
+            if item_type is prp:
+                prop = iterator.popleft()
+                if type_ not in prop.cascade:
+                    continue
+                queue = deque(prop.cascade_iterator(type_, parent_state, 
+                            visited_instances, halt_on))
+                if queue:
+                    visitables.append((queue,mpp, None))
+            elif item_type is mpp:
+                instance, instance_mapper, corresponding_state  = \
+                                iterator.popleft()
+                yield (instance, instance_mapper)
+                visitables.append((deque(instance_mapper._props.values()), 
+                                        prp, corresponding_state))
 
     @_memoized_compiled_property
     def _compiled_cache(self):
diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index a5e6930b2..4efd2acc9 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -868,7 +868,8 @@ class RelationshipProperty(StrategizedProperty):
                     # cascade using the mapper local to this 
                     # object, so that its individual properties are located
                     instance_mapper = instance_state.manager.mapper
-                    yield (c, instance_mapper, instance_state)
+                    yield c, instance_mapper, instance_state
+            
 
     def _add_reverse_property(self, key):
         other = self.mapper.get_property(key, _compile_mappers=False)