Re: [Django] #27267: Renaming a primary key fails with "cannot drop constraint on table because other objects depend on it"

[Django]

#27267: Renaming a primary key fails with "cannot drop constraint on table 
because
other objects depend on it"
--------------------------------+--------------------------------------
     Reporter:  Melvyn Sopacua  |                    Owner:  nobody
         Type:  Bug             |                   Status:  closed
    Component:  Migrations      |                  Version:  1.8
     Severity:  Normal          |               Resolution:  needsinfo
     Keywords:                  |             Triage Stage:  Unreviewed
    Has patch:  0               |      Needs documentation:  0
  Needs tests:  0               |  Patch needs improvement:  0
Easy pickings:  0               |                    UI/UX:  0
--------------------------------+--------------------------------------

Comment (by Stephan Doliov):

 For what it is worth, I encountered the same error.
 I am using Django 2.01 and Postgres 9.6

 I have a workaround for the problem simply by declaring my migration to be
 non-atomic
 {{{    atomic = False}}}

 Here is what it looks like in practice for me. For certain migrations, I
 initialize them with data; if I undo the migration, I also want to clear
 out that seed data, in the right order as all my OneToOneFields have
 models.PROTECT declared, like so
 {{{
     guid = models.OneToOneField(Guid, on_delete=models.PROTECT,
 primary_key=True)
 }}}

 so then my migrations looks like
 {{{
 # Generated by Django 2.0.2 on 2018-03-07 23:52

 from django.core import management
 from django.db import migrations, models

 import django.db.models.deletion

 from dim.models import Guid, Role

 def create_fixture(apps, schema_editor):
     management.call_command('dumpdata', 'dim.Role', format='json',
                             indent=4,
 output='dim/fixtures/000002_dim_role.json'
                            )

 def init_data(apps, schema_editor):
     Role.objects.create(guid=Guid.objects.create(), name="Basic Consumer")
     Role.objects.create(guid=Guid.objects.create(), name="Basic
 Publisher")

 def clear_data(apps, schema_editor):
     import pdb
     pdb.set_trace()
     for role in Role.objects.all():
         guid = role.guid.guid
         role.delete(purge=True)
         Guid.objects.get(guid=guid).delete(purge=True)
     migrations.RunSQL("drop table dim_role cascade")

 class Migration(migrations.Migration):

     atomic = False

     dependencies = [
         ('dim', '0001_initial'),
     ]

     operations = [
         migrations.CreateModel(
             name='Role',
             fields=[
                 ('guid',
 models.OneToOneField(on_delete=django.db.models.deletion.PROTECT,
 primary_key=True, serialize=False, to='dim.Guid')),
                 ('name', models.CharField(max_length=64, unique=True,
 verbose_name='name')),
                 ('created_ts', models.DateTimeField(auto_now_add=True)),
                 ('updated_ts', models.DateTimeField(auto_now=True,
 null=True)),
                 ('deleted_ts', models.DateTimeField(null=True)),
             ],
             options={
                 'verbose_name': 'role',
                 'verbose_name_plural': 'roles',
                 'db_table': 'dim_role',
             },
         ),
         migrations.RunPython(init_data, reverse_code=clear_data),
         migrations.RunPython(create_fixture,
 reverse_code=migrations.RunPython.noop)
     ]
 }}}

-- 
Ticket URL: <https://code.djangoproject.com/ticket/27267#comment:15>
Django <https://code.djangoproject.com/>
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