Django code executed by post_save signal happens within atomic transaction

Question

Upgrading to Django 1.6 has introduced a tricky problem into my code: database operations that are triggered by a post_save signal are getting contained within the with transaction.atomic(): block of Django's get_or_create().

The impact for me is that custom sql (unmanaged) isn't getting committed to the db in time.

Is there a different signal that I can use that gets sent after obj.save() exits its atomic block?

Or have I diagnosed this wrong?

Answer 1

Django's get_or_create() executes its save() in an atomic block, and signals fired post_save are nested within that atomic block.

My workaround was to override the native get_or_create() with my own version in a custom manager, without the transaction.atomic() block.

Answer 2

for the signal to function properly you need out of the atomic transaction, because in the midst of shooting transsaccion signal without the commmit in the database.

Answer 3

Old question, but I came across this today.

Django >=1.9 supports transaction.on_commit hooks.

Here's how my resulting code came out, and appears to behave as expected:

from django.db import transaction

def my_post_save_hook(sender, instance):
    transaction.on_commit(
        lambda: do_the_thing()
    )

post_save.connect(my_post_save_hook, sender=MyModel)