#33579: Raise a specialized exception when Model.save(update_fields) does not
affect any rows
-------------------------------------+-------------------------------------
Reporter: Simon Charette | Owner: Dulalet
Type: New feature | Status: assigned
Component: Database layer | Version: 4.0
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 1
Needs tests: 1 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
> I'd vote to remove it totally 😉, we don't raise any exception on save()
without update_fields.
As annoying as this exception can be I don't think we should entirely
silence it. Passing `update_fields` is synonymous with `force_update` and
just like when `force_insert` is provided erroring out to let callers know
that the forced operation failed seems like the right thing to do as doing
otherwise could result in unexpected data loses.
At least with a specialized exception, something less generic than
`DatabaseError`, callers can more adequately react to such errors. For
example, raised `ObjectNotUpdated` can be turned into a 404, silenced, or
turn into a subsequent `save` call without update fields depending on the
situation.
If you look at the ''core'' usages of `save(update_fields)` there seems to
be cases where we'd want to do one over the other. For example,
`reverse_many_to_one_manager._clear` might want to silence such exceptions
[https://github.com/django/django/blob/de1117ea8eabe0ee0aa048e5a4e249eab7c4245e/django/db/models/fields/related_descriptors.py#L909
when assigning] `None` while in `RenameContentType._rename` you'd most
like would want to refetch the row by natural key and update it again.
Once the exception lands and is documented it could allow third party
tools like DRF to catch them on `PUT` / `PATCH` and turn them into 404s.
Given the patch has not been improved for over 6 months I'll assign it to
me and try to bring it through the finish line.
--
Ticket URL: <https://code.djangoproject.com/ticket/33579#comment:14>
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