#28297: Same queryset result in two different queries on ORM
-------------------------------------+-------------------------------------
Reporter: Marcus Renno | Owner: Tom
Type: Bug | Status: assigned
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: join, annotation, F | 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 Tom):
I've dug into this a fair bit and I'm sorry to say I'm stuck. I also think
there is a pretty big bug lurking here that is out of my league. Or maybe
it's a feature we don't support?
As far as I can tell, if you do:
{{{
Publisher.objects
.annotate(num_books=Count('book', distinct=True))
.filter(book__rating__gt=3.0)
.annotate(num_rated=Count('book', distinct=True))
.filter(num_books=F('num_rated'))
}}}
Then the resulting SQL will have the following `HAVING` clause:
`HAVING COUNT(DISTINCT "publisher"."id") = (COUNT(DISTINCT
"publisher"."id"))`
Am I correct in thinking that this should be:
`HAVING COUNT(DISTINCT "publisher"."id") = (COUNT(DISTINCT "T3"."id"))`,
where `T3` is the correct join?
In any case, either the generated query is incorrect or the documentation
needs to be updated.
I think, at least in the case of a m2m join, one of the issues are that
there seems to be no way to resolve which alias is used by two identical
annotations which are affected by a previous `.filter()` in the
`query.join` method.
--
Ticket URL: <https://code.djangoproject.com/ticket/28297#comment:20>
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