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?

apparently this has been a [ticket/discussion for years now](https://code.djangoproject.com/ticket/14051)... which led me to [this module](https://github.com/aaugustin/django-transaction-signals) which adds transaction-level signals. — probabble, Feb 12 '14 at 23:22
but to clarify the question: is the post_save signal getting fired from within that atomic block, causing all code run by that signal to be executed with autocommit turned off? — probabble, Feb 12 '14 at 23:24

score 6 · Accepted Answer · answered Feb 13 '14 at 18:37

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.

score 0 · Answer 2 · answered Sep 04 '15 at 13:45

0

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.

answered Sep 04 '15 at 13:45

alfonsoolavarria

1,141
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11

score 0 · Answer 3 · answered Oct 07 '21 at 15:56

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)

Django code executed by post_save signal happens within atomic transaction

3 Answers3