#23673: IntegrityError when using a ManyToMany relation to add a model instance
with unique constraint.
-------------------------------------+-------------------------------------
Reporter: jo-soft | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 1.7
(models, ORM) | Resolution:
Severity: Normal | worksforme
Keywords: ManyToManyField, | Triage Stage:
get_or_create | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by bmispelon):
* status: new => closed
* needs_better_patch: => 0
* resolution: => worksforme
* needs_tests: => 0
* needs_docs: => 0
Comment:
Hi,
It seems to me that things are working as intended.
In your example, when you use `m.m2m`, you basically get a queryset that's
equivalent to `M2.objects.filter(m1=m)`.
So when you do `m.m2m.get_or_create(name='foo')`, you're doing
M2.objects.filter(m1=m).get_or_create(name='foo')`.
If there's a M2 element with a name `foo` but which doesn't appear in
`m.m2m`, then by definition `get_or_create` will attempty to create it.
This is of course not possible because of the unique constraint on the
name, so you get the `IntegrityError`.
Closing this as `worksforme`. Please reopen if I've misunderstood your
issue.
Thanks.
--
Ticket URL: <https://code.djangoproject.com/ticket/23673#comment:1>
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