#25081: QuerySet.get() ignores order_by in DISTINCT ON queries
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Reporter: pdewacht | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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The following query, using the PostgreSQL-specific DISTINCT ON, is
mistranslated:
{{{
Model.objects.order_by('key', '-last_updated').distinct('key').get(key=x)
}}}
This generated this SQL query:
{{{
SELECT DISTINCT ON ("bug_mymodel"."key")
"bug_mymodel"."id", "bug_mymodel"."key", "bug_mymodel"."last_updated",
"bug_mymodel"."text"
FROM "bug_mymodel"
WHERE "bug_mymodel"."key" = 'xyz'
}}}
The ORDER BY request is omitted from the query, but DISTINCT ON is
meaningless without sort order. Note that it is correct to use get() in
this case, as it is guaranteed that there is only one result.
We expected the following SQL:
{{{
SELECT DISTINCT ON ("bug_mymodel"."key")
"bug_mymodel"."id", "bug_mymodel"."key", "bug_mymodel"."last_updated",
"bug_mymodel"."text"
FROM "bug_mymodel"
WHERE "bug_mymodel"."key" = 'xyz'
ORDER BY "bug_mymodel"."key" ASC, "bug_mymodel"."last_updated" DESC
}}}
Full test case:
{{{
class MyModel(models.Model):
key = models.CharField(max_length=100)
last_updated = models.DateTimeField(auto_now=True)
text = models.CharField(max_length=100)
def test():
return MyModel.objects.order_by('key',
'-last_updated').distinct('key').get(key='xyz')
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25081>
Django <https://code.djangoproject.com/>
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