#33403: Annotate results change when filtering *after* the annotate
-------------------------------------+-------------------------------------
Reporter: karyon | Owner: nobody
Type: Uncategorized | Status: closed
Component: Database layer | Version: 4.0
(models, ORM) |
Severity: Normal | Resolution: invalid
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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Changes (by Simon Charette):
* status: new => closed
* resolution: => invalid
Comment:
While the documentation doesn't explicit mention this particular
combination you are effectively hitting #10060 where the `book` table is
joined twice because instead of a single time and used for aggregation and
filtering.
In order to avoid this problem you can use a `FilteredRelation` alias or
simply the `condition` argument of `Sum`
{{{#!python
Publisher.objects.annotate(Sum("books__pages",
condition=Q(books__in=Book.objects.all()))
Publisher.objects.alias(
filtered_books=FilteredRelation("books",
condition=Q(books__in=Book.objects.all()))
).annotate(
Sum("filtered_books__pages"),
)
}}}
Please TicketClosingReasons/UseSupportChannels in the future for this kind
of questions
---
I kind of wish we made `FiltereRelation(relation: str, condition: Q)`
`Relation(relation: str, condition: Optional[Q])` instead and documented
its usage to circumvent this problem with the use of `alias` to ''tell''
the ORM a JOIN **must** be reused.
--
Ticket URL: <https://code.djangoproject.com/ticket/33403#comment:3>
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