Django migration fails on unqiue_together with model subclass references

[David Binetti]

I've searched around and can't find a bug for this behavior, so here goes...

With this model inheritance:

class Account(models.Model):
    name = models.CharField (...)
   
class Source(models.Model):
    name = models.CharField(...)
    account = models.ForeignKey('Account', related_name='sources')

class SubSource(Source):
    uid = models.CharField(...)

    class Meta:
        unique_together = (
            ("account", "uid"),
        )

My intended behavior here is to ensure I can only have a single combination of Accounts and (external) SubSources. I may have multiple instances of the same external sub-source on the table if used by different accounts, which is why i'm not simply using unique on the uid field.

I can run django-admin.py check, which passes, and django-admin.py makemigrations, which passes. But when i try to run django-admin.py migrate it fails with:

django.db.utils.ProgrammingError: column "account_id" named in key does not exist

the generated migration script looks like this:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models, migrations


class Migration(migrations.Migration):

    dependencies = [
        <snip>
    ]

    operations = [
        migrations.AlterUniqueTogether(
            name='subsource',
            unique_together=set([('account', 'uid')]),
        ),
    ]

I'm sorry that I'm not skilled enough to produce an actual test case. Thanks.

[Simon Charette]

The real issue here is that you shouldn't be allowed to include non-local fields in unique_together. An additional check was added in #22356 which has been merged into master.

I'm wondering why I didn't backport it to 1.7 right away. Since this can lead to invalid migrations being created we might want to include it in 1.7.1?