#34280: Support create defaults for update_or_create
-------------------------------------+-------------------------------------
Reporter: Timothy | Owner: nobody
Schilling |
Type: New | Status: assigned
feature |
Component: Database | Version: dev
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
I proposed the idea of extending `update_or_create` to support specifying
a different set of defaults for the create operation on the
[forum](https://forum.djangoproject.com/t/feature-idea-update-or-create-
to-allow-different-defaults-for-create-and-update-operations/18300/15).
There seems to be consensus it's a positive add to Django.
Adam raised concerns with my proposed approach of adding a
`create_defaults` parameter to the function since this would conflict with
any fields on a model named, `create_defaults`. Jeff did a code search on
github for that term and didn't find any matches. I suspect if someone
where using a field named `create_defaults`, it would be a JSON or object
type field. Those don't seem like reasonable candidates to be part of a
`UniqueConstraint`, which should be underlying the look-up arguments to
`update_or_create`.
I do like the idea of having a separate parameter for `create_defaults`,
but if we must preserve 100% backwards compatibility, Adam's suggestion of
having defaults be set to another object makes the most sense.
My blocking question is, which approach should I take?
From the forum post:
I’ve run into a use-case in which it’d be helpful to have the ability
to specify a different set of defaults for the update operation compared
to the create operation. While I don’t expect my particular use case to
translate, here’s a more generic one.
Given the following Record model:
{{{
class Record(models.Model):
some_id = models.CharField(unique=True)
created_by = models.ForeignKey(User, ...)
modified_by = models.ForeignKey(User, null=True, blank=True, ...)
}}}
When a record is created, we would want to set created_by, but if it’s
being updated, we’d want to set modified_by. This use case can’t be solved
by using update_or_create, unless it allows for us to specify a different
set of default values.
{{{
Record.objects.update_or_create(
some_id=some_value,
defaults={"modified_by": user},
create_defaults={"created_by": user},
)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/34280>
Django <https://code.djangoproject.com/>
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