rework to expire() to make it smarter. when you expire(), history is immediately removed as well as explicit from dirty/deleted lists. this also changes uow.rollback_object() to remove from those lists, which is strange that it didnt do that before. anyway the mapper, when selecting and creating instances, asks the uow if this already identity-mapped instance is expired, and if so refreshes it on the fly, saving the need for the re-_get() operation, if some other query happens to touch upon the expired object. unit test added to confirm this.

3 files changed, 25 insertions, 5 deletions

diff --git a/lib/sqlalchemy/mapping/mapper.py b/lib/sqlalchemy/mapping/mapper.py
index 1efdb649a..8ff28cf56 100644
--- a/lib/sqlalchemy/mapping/mapper.py
+++ b/lib/sqlalchemy/mapping/mapper.py
@@ -816,16 +816,16 @@ class Mapper(object):
         # including modifying any of its related items lists, as its already
         # been exposed to being modified by the application.
         identitykey = self._identity_key(row)
-        if objectstore.get_session().has_key(identitykey):
-            instance = objectstore.get_session()._get(identitykey)
+        sess = objectstore.get_session()
+        if sess.has_key(identitykey):
+            instance = sess._get(identitykey)
 
             isnew = False
-            if populate_existing:
+            if populate_existing or sess.is_expired(instance, unexpire=True):
                 if not imap.has_key(identitykey):
                     imap[identitykey] = instance
                 for prop in self.props.values():
                     prop.execute(instance, row, identitykey, imap, True)
-
             if self.extension.append_result(self, row, imap, result, instance, isnew, populate_existing=populate_existing):
                 if result is not None:
                     result.append_nohistory(instance)
diff --git a/lib/sqlalchemy/mapping/objectstore.py b/lib/sqlalchemy/mapping/objectstore.py
index d6b476562..7827c1b78 100644
--- a/lib/sqlalchemy/mapping/objectstore.py
+++ b/lib/sqlalchemy/mapping/objectstore.py
@@ -166,7 +166,7 @@ class Session(object):
         """invalidates the data in the given objects and sets them to refresh themselves
         the next time they are requested."""
         for o in obj:
-            global_attributes.trigger_history(o, lambda: refresh(o))
+            self.uow.expire(o)
 
     def expunge(self, *obj):
         for o in obj:
diff --git a/lib/sqlalchemy/mapping/unitofwork.py b/lib/sqlalchemy/mapping/unitofwork.py
index fc589f65b..0b392b447 100644
--- a/lib/sqlalchemy/mapping/unitofwork.py
+++ b/lib/sqlalchemy/mapping/unitofwork.py
@@ -100,6 +100,18 @@ class UnitOfWork(object):
         self.rollback_object(obj)
         object_mapper(obj)._get(obj._instance_key, reload=True)
 
+    def expire(self, obj):
+        self.rollback_object(obj)
+        def exp():
+            object_mapper(obj)._get(obj._instance_key, reload=True)
+        global_attributes.trigger_history(obj, exp)
+    
+    def is_expired(self, obj, unexpire=False):
+        ret = global_attributes.has_trigger(obj)
+        if ret and unexpire:
+            global_attributes.untrigger_history(obj)
+        return ret
+            
     def has_key(self, key):
         """returns True if the given key is present in this UnitOfWork's identity map."""
         return self.identity_map.has_key(key)
@@ -247,6 +259,14 @@ class UnitOfWork(object):
     def rollback_object(self, obj):
         """'rolls back' the attributes that have been changed on an object instance."""
         self.attributes.rollback(obj)
+        try:
+            del self.dirty[obj]
+        except KeyError:
+            pass
+        try:
+            del self.deleted[obj]
+        except KeyError:
+            pass
             
 class UOWTransaction(object):
     """handles the details of organizing and executing transaction tasks