#28296: Add support for aggregation through subqueries
-------------------------------------+-------------------------------------
Reporter: László Károlyi | Owner: B
| Martsberger
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Comment (by B Martsberger):
Matt, I'm not sure your use case will be improved by this ticket due to
the need to group by a computed field. But it also looks like it's not
necessary to subclass Subquery with a new template.
{{{
event_day_subquery = Subquery(
Event.objects.annotate(day=TruncDay('timestamp'))
.values('project_id', 'day')
.annotate(cnt=Count(Value(1)))
.values('cnt')
.filter(project_id=OuterRef('id'))
Player.objects.annotate(day_count=event_day_count).values('id',
'day_count')
}}}
Produces SQL like
{{{
SELECT "player_player"."id",
(SELECT COUNT(1) AS "cnt"
FROM "player_event" U0
WHERE U0."player_id" = "player_player"."id"
GROUP BY U0."player_id",
DATE_TRUNC('day', U0."timestamp" )) AS "day_count"
FROM "player_player"
}}}
Replying to [comment:17 Matt Hegarty]:
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Ticket URL: <https://code.djangoproject.com/ticket/28296#comment:18>
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