#35833: Annotation yielding an empty set causes entire QuerySet to become empty
-------------------------------------+-------------------------------------
Reporter: Jacob Walls | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 5.1 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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With a nullable JSONField in my model:
{{{
class TileModel(models.Model):
provisionaledits = JSONField(null=True)
}}}
If I then annotate with a set-returning function (e.g.
JSONB_ARRAY_ELEMENTS on postgres) that happens to return an empty set, the
entire QuerySet is zeroed out.
{{{
In [1]: from django.db.models import Func, F
In [2]: from arches.app.models.models import TileModel
In [3]: class JsonbArrayElements(Func):
...: arity = 1
...: contains_subquery = True # Django 5.2: set_returning = True
...: function = "JSONB_ARRAY_ELEMENTS"
...:
In [4]: TileModel.objects.count()
Out[4]: 9
In [5]:
TileModel.objects.annotate(empty_set=JsonbArrayElements(F("provisionaledits")))
Out[5]: <QuerySet []>
}}}
I distilled this from a more complicated failure. If it helps, here is a
query that fails more helpfully when you actually have JSON in the queried
field but still can't extract array elements because it's not an array:
{{{
In [14]: TileModel.objects.create(provisionaledits={})
Out[14]: <TileModel: TileModel object
(6ee450f7-b516-4c61-b6e7-52e876b878fe)>
In [15]:
TileModel.objects.annotate(no_longer_empty=JsonbArrayElements(F("provisionaledits")))
Out[15]: DataError: cannot extract elements from an object
}}}
I guess I would expect an error in both cases instead of an empty queryset
in the former. At the very least, I would only expect the annotation to
yield some sort of empty value, not for the whole queryset to silently
become empty.
--
Ticket URL: <https://code.djangoproject.com/ticket/35833>
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