#28296: Add support for aggregation through subqueries
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Reporter: László Károlyi | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(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
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Comment (by Sylvain Zimmer):
Hello !
I solved this with a custom class:
{{{#!python
class SubQueryCount(Subquery):
output_field = models.IntegerField()
def __init__(self, *args, **kwargs):
Subquery.__init__(self, *args, **kwargs)
self.queryset =
self.queryset.annotate(cnt=Count("*")).values("cnt")
self.queryset.query.set_group_by() # values() adds a GROUP BY we
don't want here
subquery = Media.objects.filter(artist=OuterRef('id'))
artists_with_count_medias =
Artist.objects.all().annotate(count_medias=SubQueryCount(subquery))
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/28296#comment:5>
Django <https://code.djangoproject.com/>
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