#28296: Subquery with annotation fails without tweaking
-------------------------------------+-------------------------------------
Reporter: László Károlyi | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
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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Comment (by Simon Charette):
Hello László,
It's not clear to me why you not expecting a `GROUP BY` statement to be
present in the subquery when you are explicitly grouping by `id` by using
`values('id')` before annotating. Please see the section about aggregation
and the usage of `values()` to `GROUP BY` in the
[https://docs.djangoproject.com/en/1.11/topics/db/aggregation/#order-of-
annotate-and-values-clauses aggregation documentation].
Also, is there a reason you are not simply using
[https://docs.djangoproject.com/en/1.11/ref/models/conditional-expressions
/#conditional-aggregation conditional aggregation] for this query instead?
{{{#!python
Performance.objects.annotate(
reserved_seats=Count(
Case(When(seat_reservations__status__in=TAKEN_TYPES,
then='seat_reservations')),
),
)
}}}
Note that I'm assuming `SeatReservation.performance.related_name ==
'seat_reservations'` above.
--
Ticket URL: <https://code.djangoproject.com/ticket/28296#comment:1>
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