Django post_save preventing recursion without overriding model save()

python django django-signals
Yuji 'Tomita' Tomita picture Yuji 'Tomita' Tomita · May 31, 2012 · Viewed 20k times · Source

There are many Stack Overflow posts about recursion using the post_save signal, to which the comments and answers are overwhelmingly: "why not override save()" or a save that is only fired upon created == True.

Well I believe there's a good case for not using save() - for example, I am adding a temporary application that handles order fulfillment data completely separate from our Order model.

The rest of the framework is blissfully unaware of the fulfillment application and using post_save hooks isolates all fulfillment related code from our Order model.

If we drop the fulfillment service, nothing about our core code has to change. We delete the fulfillment app, and that's it.

So, are there any decent methods to ensure the post_save signal doesn't fire the same handler twice?

Answer

mossplix picture mossplix · May 31, 2012

you can use update instead of save in the signal handler

queryset.filter(pk=instance.pk).update(....)

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