Multi-table inheritance with only related fields results in invalid migration on MySQL

[Hubert Bielenia]

This report may be a duplicate of #24424 , but since the scope is somewhat different and proposed fix would not solve the issue, I decided to report it separately.

On Django 1.8.2, I have following model:

class Client(User):
    mailing_list = models.OneToOneField(SubscriberList, null=True, default=None)

Using manage.py makemigrations generates following operations:

 operations = [
        migrations.CreateModel(
            name='Client',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('user', models.OneToOneField(to=settings.AUTH_USER_MODEL)),
            ],
        ),
        migrations.RemoveField(
            model_name='client',
            name='id',
        ),
        migrations.RemoveField(
            model_name='client',
            name='user',
        ),
        migrations.AddField(
            model_name='client',
            name='mailing_list',
            field=models.OneToOneField(null=True, default=None, to='campaign.SubscriberList'),
        ),
        migrations.AddField(
            model_name='client',
            name='user_ptr',
            field=models.OneToOneField(parent_link=True, auto_created=True, primary_key=True, default=0, serialize=False, to=settings.AUTH_USER_MODEL),
            preserve_default=False,
        ),
]

As you can see, the migration starts by removing implicit id and user fields, to later substitute them with implicit user_ptr field that serves both as foreign and primary key. Unfortunately, migrations.RemoveField uses ALTER TABLE statements, and this code attempts to delete all columns on the table, resulting in OperationalError with MySQL 5.8:
django.db.utils.OperationalError: (1090, "You can't delete all columns with ALTER TABLE; use DROP TABLE instead").

It looks to me like an unwanted behaviour.

[Abhaya Agarwal]

I'm trying to reproduce it but for me, the following correct Migration is being generated:

    operations = [ 
        migrations.CreateModel(
            name='client',
            fields=[
                ('user_ptr', models.OneToOneField(parent_link=True, auto_created=True, primary_key=True, serialize=False, to=settings.AUTH_USER_MODEL)),
                ('mailing_list', models.OneToOneField(null=True, default=None, to='bug.SubscriberList')),
            ],  
            options={
                'abstract': False,
                'verbose_name': 'user',
                'verbose_name_plural': 'users',
            },  
            bases=('auth.user',),
            managers=[
                ('objects', django.contrib.auth.models.UserManager()),
            ],  
        ),  
    ] 

Can you provide a complete set of model definitions that will reproduce the issue?

[Tim Graham]

We might be missing the state of the models before what is reported in the description.