#28477: Strip unused annotations from count queries
-------------------------------------+-------------------------------------
Reporter: Tom Forbes | Owner: Simon
Type: | Charette
Cleanup/optimization | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* needs_better_patch: 1 => 0
Comment:
I submitted [https://github.com/django/django/pull/16263 a revised PR]
that strip unused annotations not only for `.count()` for but any usage of
`.aggregate`.
To take example from comment:7 and comment:9 the resulting query is now
{{{#!python
Person.objects.annotate(full_name=Concat('first_name', Value(' '),
'last_name')).count()
}}}
{{{#!sql
SELECT COUNT(*) FROM support_person
}}}
The adjusted logic goes along these lines.
Instead of systematically performing a subquery wrapping when there are
existing annotations only do so when the pre-existing annotation are
aggregate or window functions. In both cases, pre-existing
aggregation/window or not, strip annotations that are not referenced by
the aggregates.
--
Ticket URL: <https://code.djangoproject.com/ticket/28477#comment:13>
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