#24705: Exception when negating Q object in annotate
-------------------------------------+-------------------------------------
Reporter: karyon | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.8
(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 jarshwah):
* needs_better_patch: => 0
* stage: Unreviewed => Accepted
* needs_tests: => 0
* needs_docs: => 0
Comment:
{{{
UserProfile.objects.annotate(is_member=ExpressionWrapper(~Q(groups__name="Group
name"), output_field=BooleanField()))
}}}
Isn't really supported. Q objects are for filters or case expressions
only. They aren't designed to be used as annotations, even though they
share similar APIs (for Case/When support).
{{{
UserProfile.objects.annotate(is_member=Case(When(~Q(groups__name="Group
name"), then=Value(False)), default=Value(True),
output_field=BooleanField()))
}}}
Probably should be supported. Negating a when clause seems like something
that should be supported, but I haven't yet investigated why this is
throwing errors. For the moment, as a workaround, you can stop negating
the clause and switch the "then" and "default" values to then=True,
default=False I think.
Accepting based on the fact that negated Q objects don't work with case
expressions though.
--
Ticket URL: <https://code.djangoproject.com/ticket/24705#comment:1>
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