Re: Is this behavior with Meta Ordering and Group By expected?

Hi Eric. 

This is the expected behavior ( https://docs.djangoproject.com/en/dev/ref/models/options/#ordering ). 

If ordering is defined on model Meta, the ORDER BY SQL is included by default in all query.

to avoid this behavior, you can use order_by() without parameters: 

eg: 

A.objects.order_by().values('b').annotate(most_recent=Max('created_at'))

On Wed, Jun 29, 2016 at 5:39 PM, eric conner <ericwconner@gmail.com> wrote:

Hello!

I'm using Django 1.9.7, MySQL innodb 5.7.11, and python 2.7.10.

I noticed some strange behavior when running this query:

q = A.objects.values('b').annotate(most_recent=Max('created_at'))

Produces this SQL:

SELECT `core_a`.`b_id`, MAX(`core_a`.`created_at`) AS `most_recent` FROM `core_a` GROUP BY `core_a`.`id` ORDER BY `core_a`.`id` ASC

which groups by an unexpected field.  I was expecting it to group by `core_a`.`b_id` rather than `core_a`.`id`.

Here are my models:

from __future__ import unicode_literals

from django.db import models

from django.utils import timezone

class B(models.Model):

    created_at = models.DateTimeField(default=timezone.now)

class A(models.Model):

    created_at = models.DateTimeField(default=timezone.now)

    b = models.ForeignKey(B)

    class Meta:

        ordering = ["id"]

If I remove from model A these lines 

    class Meta:

        ordering = ["id"]

then the query produces SQL which groups by the b_id column as expected.

Is this known behavior?  Would this be considered a bug?

Thanks,

-Eric

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