#28616: DISTINCT ON and update() does the wrong thing
-------------------------------------+-------------------------------------
Reporter: Daniel | Owner: nobody
Keller |
Type: Bug | Status: new
Component: Database | Version: 1.11
layer (models, ORM) |
Severity: Normal | Keywords:
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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If I have a model like
{{{
from django.db import models
from django.utils import timezone
class Foo(models.Model):
num = models.IntegerField(default=0)
date = models.DateTimeField(default=timezone.now)
flag = models.BooleanField(default=False)
}}}
and (with Postgresql) I do
{{{
Foo.objects.order_by('num', '-date').distinct('num').only('pk')
}}}
I get a query like
{{{
SELECT DISTINCT ON ("app_foo"."num") "app_foo"."id" AS Col1 FROM "app_foo"
ORDER BY "app_foo"."num" ASC, "app_foo"."date" DESC; args=()
}}}
which returns the latest `Foo` for each `num`.
BUT, if I do
{{{
Foo.objects.order_by('num', '-date').distinct('num').update(flag=True)
}}}
then it executes
{{{
UPDATE "app_foo" SET "flag" = true; args=(True)
}}}
which updates ''everything''.
I don't necessarily think that this behaviour should be supported, but it
would be nice to at least get a `NotImplementedError`.
--
Ticket URL: <https://code.djangoproject.com/ticket/28616>
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