I want to write a SessionExtension that fires a 'Foo-created' event or 'Bar-created' event every time a new Foo or new Bar is committed to the database. However, once inside the after_commit method, I don't know where to find which entities have been committed. Where do I get this information?
+2
A:
The Session instance has attribute new, dirty, deleted holding added, updated and deleted objects respectively. They will be already empty when after_commit is executed, but they are available in after_flush. You can extent your own list of added instances for each flush in after_flush hook and use them for events and clear in after_commit.
Denis Otkidach
2010-05-24 10:54:02
Okay, so I copy `new` in `after_flush` and then use that in `after_commit`? Sounds simple enough. Thanks!
Dan Ellis
2010-05-25 18:48:22
Okay, but the problem I then have is that the newly-created instance doesn't have its relationship attributes set. For example, `author_id` is an integer, but `author` is `None`. Is there some better way to fix that than making the relationship lazy, which would be a bit leaky?
Dan Ellis
2010-05-26 01:52:47
I just checked, and relationships are lazily loaded by default anyway, so I'm not sure what to do. Might have to go to the mailing list for this one.
Dan Ellis
2010-05-26 01:59:19
A:
Look at the Mapper Extension bits. It provides you before/after insert/update/delete hooks that you can place your code for this kind of thing.
http://www.sqlalchemy.org/docs/mappers.html?highlight=mapper%20extension#extending-mapper
Rick
2010-05-24 11:05:39
Yes, but the problem there is that they might not make it into the database, for any number of reasons.
Dan Ellis
2010-05-25 18:46:23