Re: persistence and __setstate__

>>>>> "JH" == Jeremy Hylton <[email protected]> writes:

    JH> A potential concern for any solution: If the object is updated
    JH> on demand, it is probably important to execute the change as a
    JH> separate transaction.  If you don't, then the object update
    JH> gets mixed in with arbitrary updates to other objects, which
    JH> unnecessarily complicates undo.

    BAW> That's a good point, and sounds like the first approach might
    BAW> work better.  Would the __setstate__ itself be able to do a
    BAW> transaction commit if it updated the object?  If so, that
    BAW> might be enough, if inefficient for updating a large number
    BAW> of objects.  Hmm.

    JH> How can you tell if __setstate__ updated the object?  It
    JH> always updates the object :-(.

Actually, I meant if __setstate__() updated the object's schema.
Maybe I should have said "upgrade" instead of "update".
__setstate__() should always know if this was the case or not, e.g.:

    def __setstate__(self, d):
        # ...
	upgraded = 0
	if not d.has_key('newattr1'):
	    self.newattr1 = 'blah'
	    upgraded = 1
	if not d.has_key('newattr2'):
	    self.newattr2 = 'fleh'
	    upgraded = 1
	if upgraded:
	    somehow_commit_a_transaction_with_the_new_object_state()

-Barry