Hi David.
This is https://code.djangoproject.com/ticket/33996 I think — it's a
Release Blocker for 4.1.2
Your thoughts/review on work there would be welcome. :)
Kind Regards,
Carlton
On Thu, 8 Sept 2022 at 14:30, David Sanders <shang.xiao.sand...@gmail.com>
wrote:
> Hi folks,
>
> I've noticed a difference in the way check constraint validation behaves
> compared to the way Postgres (assuming similar behaviour in other DBs)
> validates when dealing with NULLs.
>
> Given a model with a simple positive check constraint:
>
> class Test(Model):
> test = IntegerField(null=True)
>
> class Meta:
> constraints = [
> CheckConstraint(check=Q(test__gte=0), name="positive"),
> ]
>
> Then the an instance with a NULL will save but fail validation:
>
> test = Test()
> test.save()
> test.validate_constraints()
> ...
> E django.core.exceptions.ValidationError: {'__all__':
> ['Constraint “positive” is violated.']}
>
>
> I believe this is due to the way validation is handled in the WHERE
> clause. I've trawled back through the PR discussion and original ticket
> as well as the validation code – I could see the original comment about
> moving validation to WHERE to get around issues with using SELECT but
> couldn't find any other mention about how NULLs should be handled.
>
> I wanted to check with folks here first before raising an issue. I'm not
> sure what the fix should be but I'd recommend at least adding a note in the
> docs if it's not fixable? :)
>
> Cheers,
> David
>
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