#32658: Subquery ignores query ordering
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Reporter: Bálint | Owner: nobody
Balina |
Type: | Status: new
Uncategorized |
Component: Database | Version: 3.2
layer (models, ORM) | Keywords: Subquery,
Severity: Normal | annotations, ordering
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I've started migrating a huge project from Django==2.2 to ==3.2, and many
tests started to fail, because of the problem below:
When using a query with ordering in an annotated Subquery, the query's
ordering is ignored (or removed).
In a bare new Django project, I have successfully reproduced the issue:
{{{
from django.db import models
class MyModel(models.Model):
parent = models.ForeignKey(to='self', on_delete=models.CASCADE,
null=True)
name = models.TextField()
}}}
{{{
MyModel.objects.create(name='parent')
MyModel.objects.create(name='b', parent=parent)
MyModel.objects.create(name='a', parent=parent)
}}}
{{{
children_query =
MyModel.objects.filter(parent=OuterRef('pk')).annotate(child_names=Func(F('name'),
function='group_concat')).values('child_names').order_by('name')
parent_query =
MyModel.objects.annotate(child_names=Subquery(children_query))
parent_query.query.__str__()
}}}
Outputs:
{{{
SELECT "app_mymodel"."id", "app_mymodel"."parent_id",
"app_mymodel"."name", (SELECT group_concat(U0."name") AS "child_names"
FROM "app_mymodel" U0 WHERE U0."parent_id" = "app_mymodel"."id") AS
"child_names" FROM "app_mymodel"
}}}
The only thing I do, is pip install Django==2.2, run the same thing in a
shell and:
Outputs:
{{{
SELECT "app_mymodel"."id", "app_mymodel"."parent_id",
"app_mymodel"."name", (SELECT group_concat(U0."name") AS "child_names"
FROM "app_mymodel" U0 WHERE U0."parent_id" = ("app_mymodel"."id") ORDER BY
U0."name" ASC) AS "child_names" FROM "app_mymodel"
}}}
Notice the ORDER BY U0."name" ASC is missing in Django 3.2, though I have
explicitly set the ordering on the query. This happens both on SQLite and
PostgreSQL backends.
--
Ticket URL: <https://code.djangoproject.com/ticket/32658>
Django <https://code.djangoproject.com/>
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