#34754 closed Bug (fixed)
CheckConstraint with isnull lookup on JSONField transform None into null jsonb value
Reported by: | Alexandre Collet | Owned by: | Simon Charette |
---|---|---|---|
Component: | Database layer (models, ORM) | Version: | 4.2 |
Severity: | Release blocker | Keywords: | constraint, jsonfield, none, check |
Cc: | Simon Charette | Triage Stage: | Ready for checkin |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
Hello !
I think i've found a bug in the validation of constraints for the JSONField with the isnull lookup (with postgresql).
Let me explain:
I have a model with some values stored in a JSONField and i want to be sure (with a CheckConstraint) than if this field was not None, an author was set.
class MyModel(Model, UuidMixin, TimestampableMixin): values = JSONField( null=True, blank=True, ) author = ForeignKey( null=True, blank=True, to=settings.AUTH_USER_MODEL, on_delete=SET_NULL, ) class Meta: constraints = [ CheckConstraint( name="author_cannot_be_null_if_values_was_set", check=( Q(values__isnull=True) | Q(values__isnull=False, author__isnull=False) ), ), ]
This works perfectly in 4.1.
But in 4.2, the sql generated for the check when i does not set the field "values" and "author" is that:
instance = MyModel(values=None, author=None) instance.validate_constraints()
SELECT 1 AS "_check" WHERE COALESCE((('null'::jsonb IS NULL OR (NULL IS NOT NULL AND 'null'::jsonb IS NOT NULL))), true)
This raise a ValidationError because the None value was transformed into a jsonb null value and the isnull lookup is always False.
I'm not sure how to correct this, but if anyone would like to help me, I'd be delighted to make a pull request.
Change History (8)
comment:1 by , 17 months ago
Type: | Uncategorized → Bug |
---|
comment:2 by , 17 months ago
Keywords: | jsonfield none check added |
---|
comment:3 by , 17 months ago
Cc: | added |
---|---|
Severity: | Normal → Release blocker |
Triage Stage: | Unreviewed → Accepted |
comment:4 by , 17 months ago
Has patch: | set |
---|---|
Owner: | changed from | to
Status: | new → assigned |
Submitted a patch to address the issue but I think the fundamental problem here is that
MyModel.objects.create(values=None) # Creates an object with a SQL NULL MyModel.objects.filter(values=None) # Filters for objects with JSON NULL
This asymmetry prevents logic from being added to JSONField.get_db_prep_value
directly but it's a much larger problem to resolve.
Just like we discourage the usage of null=True, blank=True
fields as allows for the co-existence of two no data values I think we should do add friction to storing null
in a JSONField(null=True)
field by requiring that Value(None, JSONField())
be used to filter using 'null'::json
.
I can't think of a deprecation path for MyModel.objects.filter(values=None)
though unfortunately so it seems like we've missed the boat on that one.
comment:5 by , 17 months ago
Triage Stage: | Accepted → Ready for checkin |
---|
Thanks for the report. Regression in 5c23d9f0c32f166c81ecb6f3f01d5077a6084318.