#21584: prefetch_related child queryset does not update on create
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Reporter: lucaswiman | Owner: nobody
Type: Uncategorized | Status: closed
Component: Database layer | Version: 1.6
(models, ORM) | Resolution: invalid
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by lucaswiman):
> This is not a bug, I'm afraid.
It's very unintuitive that the child_set won't keep track of what
elements are in it when it is mutated by its own methods. This seems to
break the "iterable" abstraction.
>There may be some small exceptions, such as when you update a FK object,
and the FK ID on that object may be updated as well, but only those that
can be done with no dependency tracking
Isn't that precisely the behavior that's being described here? The
foreign key relationship should know that a new entry was created, because
the create method was called on the child_set itself. Create should
invalidate the cache, because there's no way the cache can remain valid
after create is called. Couldn't create set self._results_cache to None,
and self.prefetch_done to False when create is called?
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Ticket URL: <https://code.djangoproject.com/ticket/21584#comment:2>
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