#32879: Using extra instead annotate in ORM while using select_for_update
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Reporter: Zerq | Owner: nobody
Type: Uncategorized | Status: closed
Component: Database layer | Version: 3.2
(models, ORM) |
Severity: Normal | Resolution: duplicate
Keywords: QuerySet.extra | 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 Zerq):
For anyone who have the same problem:
{{{
sub =
Subquery(Bar.objects.filter(pk=OuterRef('pk')).annotate(count=Count('*')).values('count'))
sub = Coalesce(sub, 0)
query = Foo.objects.annotate(times_used=sub)
}}}
Small warning: If subquery has no values, it will return None, this is the
reason for Coalesce.
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Ticket URL: <https://code.djangoproject.com/ticket/32879#comment:4>
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