#35890: pre_save field in parent models are not called during update in
update_or_create
-------------------------------------+-------------------------------------
Reporter: Gagaro | Owner: (none)
Type: Bug | Status: new
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Changes (by Simon Charette):
* cc: Simon Charette, Florian Apolloner, Sarah Boyce (added)
Comment:
I think we need someone else to chime in here to get a consensus before
moving forward with either solution.
The `Field.auto_now` pattern is a feature on its way out #22995 and as it
doesn't play nicely with `update_fields` #22981 particularly in the
context of `update_or_create` (#35014 and associated
[https://forum.djangoproject.com/t/update-or-create-behavior/25944 forum
discussion]).
In your particular case, `Child.save(update_fields={...})`, won't update
`"modified_at"` unless it's specified explicitly so your expectations are
already broken for any direct or indirect (through third-party apps) usage
of `save(update_fields)`; `update_or_create` is only a single instance of
that.
The changes made to handle local concrete fields in #32095
([https://github.com/django/django/pull/13526 original PR by Florian],
[https://github.com/django/django/pull/16072 eventually merged changes by
Sarah]) unfortunately it didn't cover this use case,
[https://github.com/django/django/pull/13526#discussion_r503304168 even if
it was pointed out as a point of ambiguity], as neither `Book` or
`Publisher` are using MTI.
> Why do you think it should be that way?
From my perspective, given the intent #32095 was to avoid unnecessary
field updates, performing MTI inherited tables updates when non of their
fields are explicitly requested to be updated because they use a pattern
meant to be deprecated is not the right approach.
--
Ticket URL: <https://code.djangoproject.com/ticket/35890#comment:6>
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