InstrumentationManager causes problems with session if a mapper extension is in use.

[Paul Harrington]

class DummyInstrumentation(interfaces.InstrumentationManager): pass

sqlalchemy.orm.attributes.instrumentation_finders.append( lambda cls: DummyInstrumentation)

We get very odd results when using an instrumentation manager and a session extension even with dummy implementations. The problem can be reproduced by the code in the attachment against 5.3. The problem does not appear to be in 0.5.4p2 or against a checked out of the main trunk at r6099.

I guess that I am filing this for reference purposes only as we will upgrade to 0.5.4p2 to workaround the problem.

[Paul Harrington]

program that demonstrates problem with instrumentation and mapper extension

[Mike Bayer]

the default InstrumentationManager in 0.5.3 and earlier has a bug. this fixes it:

Index: lib/sqlalchemy/orm/attributes.py
===================================================================
--- lib/sqlalchemy/orm/attributes.py    (revision 6099)
+++ lib/sqlalchemy/orm/attributes.py    (working copy)
@@ -1444,7 +1444,7 @@

         # the given instance is assumed to have no state
         self._adapted.install_state(self.class_, instance, state)
-        state.dict = self._adapted.get_instance_dict(self.class_, instance)
+        #state.dict = self._adapted.get_instance_dict(self.class_, instance)
         return state

     def teardown_instance(self, instance):

the error occurs since the merge sequence causes the object to be garbage collected, then resurrected, but using the wrong dictionary due to the line above, which then makes it look like the attributes have been blanked out (hence the update).

after 0.5.3 the attributes system was overhauled, and the "resurrection" system is no longer used except in the case of mutable attributes.

[Mike Bayer]

Removing milestone: 0.5.4 (automated comment)