#20429: Add QuerySet.update_or_create method
-------------------------------------+-------------------------------------
Reporter: tunixman | Owner:
Type: New feature | elektrrrus
Component: Database layer | Status: assigned
(models, ORM) | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by loic84):
The integrity issue is just a side effect of the race-condition, even if
uniqueness is enforced at the database level, you still need to be aware
of the potential 500 you will be getting.
I agree that any `get()` followed by `create()` in user code suffers from
the same issue, but when you do it manually you have a chance to think
about the potential problems. There is a layer of opacity when you use a
queryset method like `update_or_create()` and you may assume that all
problems have been solved by the framework. Eventually you get to shoot
yourself in the foot, which results in tickets like #12579.
`update()` documents that it's free of race-condition,
`select_for_update()` is obviously free of race-condition on supported
backends, it wouldn't be too hard to assume that `update_or_create()`
provides such guarantee as well.
I agree that the race-condition for these common patterns should be
documented (if that's not already the case), but convenience methods like
`get_or_create()` and `update_or_create()` also need to be clear about
their implementation and potential consequences.
--
Ticket URL: <https://code.djangoproject.com/ticket/20429#comment:24>
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