#33137: Decouple Field.unique from select_related
-------------------------------------+-------------------------------------
Reporter: Markus Holtermann | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version:
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* cc: Simon Charette (added)
* stage: Unreviewed => Accepted
Comment:
This use case looks very similar to the [https://github.com/akaariai
/django-reverse-unique django-reverse-unique] project by Anssi which
didn't require any adjustments to the ORM and properly supported
`select_related`.
{{{#!python
class A(models.Model):
b = models.ForeignKey('B')
deleted = models.BooleanField()
class Meta:
constraints = [
UniqueConstraint(fields=['b'], condition=Q(deleted=False)),
]
class B(models.Model):
a = ReverseUnique(A, filter=Q(deleted=False))
}}}
I assume you're trying to create a subclass of `OneToOneField` that allows
specifying a `condition` and avoids having to add all of this boilerplate?
{{{#!python
class A(models.Model):
b = ConditionalOneToOne('B', condition=Q(deleted=False))
deleted = models.BooleanField()
class B(models.Model):
pass
}}}
In all cases I'm not against changing the code to use the
[https://docs.djangoproject.com/en/3.2/ref/models/fields/#attributes-for-
fields-with-relations documented] `(many|one)_to_(many|one)` attributes
instead of `unique` assuming we write a proper regression tests for them.
--
Ticket URL: <https://code.djangoproject.com/ticket/33137#comment:2>
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