#26226: Related managers should honor the queryset used for prefetching their
results.
-------------------------------------+-------------------------------------
Reporter: cancan101 | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: prefetch | Triage Stage: Ready for
| checkin
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by timgraham):
* stage: Accepted => Ready for checkin
Old description:
> This is a variation of https://code.djangoproject.com/ticket/26211 which
> does not involve multiple calls to `order_by`.
> Given these models:
>
> {{{
> class Parent(models.Model):
> pass
>
> class Child(models.Model):
> saved_dt = models.DateTimeField(auto_now_add=True)
> parent = models.ForeignKey(Parent)
> }}}
>
> why does this return `False`?:
> {{{
> >>> Parent.objects.prefetch_related(Prefetch('child_set',
> Child.objects.order_by('saved_dt'))).first().child_set.all().ordered
> False
> }}}
>
> it looks like the SQL queries generated do actually have the sort logic,
> but the query set does not reflect this fact:
>
> {{{
> SELECT "prefetch_parent"."id" FROM "prefetch_parent" ORDER BY
> "prefetch_parent"."id" ASC LIMIT 1; args=()
> SELECT "prefetch_child"."id", "prefetch_child"."saved_dt",
> "prefetch_child"."parent_id" FROM "prefetch_child" WHERE
> "prefetch_child"."parent_id" IN (1) ORDER BY "prefetch_child"."saved_dt"
> ASC; args=(1,)
> }}}
New description:
This is a variation of #26211 which does not involve multiple calls to
`order_by`.
Given these models:
{{{
class Parent(models.Model):
pass
class Child(models.Model):
saved_dt = models.DateTimeField(auto_now_add=True)
parent = models.ForeignKey(Parent)
}}}
why does this return `False`?:
{{{
>>> Parent.objects.prefetch_related(Prefetch('child_set',
Child.objects.order_by('saved_dt'))).first().child_set.all().ordered
False
}}}
it looks like the SQL queries generated do actually have the sort logic,
but the query set does not reflect this fact:
{{{
SELECT "prefetch_parent"."id" FROM "prefetch_parent" ORDER BY
"prefetch_parent"."id" ASC LIMIT 1; args=()
SELECT "prefetch_child"."id", "prefetch_child"."saved_dt",
"prefetch_child"."parent_id" FROM "prefetch_child" WHERE
"prefetch_child"."parent_id" IN (1) ORDER BY "prefetch_child"."saved_dt"
ASC; args=(1,)
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/26226#comment:6>
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