id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26211	prefetch_related with Prefetch with queryset with explicit Ordering Ignored	Alex Rothberg	nobody	"Given these models:

{{{
class Parent(models.Model):
    pass

class Child(models.Model):
    saved_dt = models.DateTimeField(auto_now_add=True)
    parent = models.ForeignKey(Parent)
}}}

I am executing this query (for each `Parent` I want to get the `child_set` in sorted order):

{{{
[m.child_set.order_by('saved_dt') for m in Parent.objects.prefetch_related(Prefetch('child_set', Child.objects.order_by('saved_dt'))).all()]
}}}

I would expect that to be two SQL queries, but in reality I see `N+2` where `N` is the number of `Child`s:


{{{
SELECT ""prefetch_parent"".""id"" FROM ""prefetch_parent""; args=()
SELECT ""prefetch_child"".""id"", ""prefetch_child"".""saved_dt"", ""prefetch_child"".""parent_id"" FROM ""prefetch_child"" WHERE ""prefetch_child"".""parent_id"" IN (1, 2) ORDER BY ""prefetch_child"".""saved_dt"" ASC; args=(1, 2)
SELECT ""prefetch_child"".""id"", ""prefetch_child"".""saved_dt"", ""prefetch_child"".""parent_id"" FROM ""prefetch_child"" WHERE ""prefetch_child"".""parent_id"" = 1 ORDER BY ""prefetch_child"".""saved_dt"" ASC LIMIT 21; args=(1,)
SELECT ""prefetch_child"".""id"", ""prefetch_child"".""saved_dt"", ""prefetch_child"".""parent_id"" FROM ""prefetch_child"" WHERE ""prefetch_child"".""parent_id"" = 2 ORDER BY ""prefetch_child"".""saved_dt"" ASC LIMIT 21; args=(2,)
}}}

I would hope that the second call to `children.order_by('saved_dt')` can return self since the queryset is already sorted by the desired key."	New feature	closed	Database layer (models, ORM)	1.9	Normal	wontfix			Unreviewed	0	0	0	0	0	0