#27764: Running migration that deletes child model (in multi-table inheritance)
backwards results in an error
------------------------------------------------+------------------------
Reporter: Alexandru Mărășteanu | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.10
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
------------------------------------------------+------------------------
1. Create two models where one of them inherits the other:
{{{
class Foo(models.Model):
test = models.CharField(max_length=256)
class Bar(Foo):
pass
}}}
2. Generate and run migrations.
`migrations/0001_initial.py` is:
{{{
...
operations = [
migrations.CreateModel(
name='Foo',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('test', models.CharField(max_length=256)),
],
),
migrations.CreateModel(
name='Bar',
fields=[
('foo_ptr', models.OneToOneField(auto_created=True,
on_delete=django.db.models.deletion.CASCADE, parent_link=True,
primary_key=True, serialize=False, to='foo.Foo')),
],
bases=('foo.foo',),
),
]
...
}}}
3. Delete the child model (`Bar`)
4. Generate and run migrations again.
`migrations/0002_auto_20170123_1212.py` is:
{{{
...
migrations.RemoveField(
model_name='bar',
name='foo_ptr',
),
migrations.DeleteModel(
name='Bar',
),
...
}}}
5. Run migrations backwards (i.e. `python migrate APP zero`)
{{{
django.db.utils.ProgrammingError: column "foo_ptr_id" of relation
"foo_bar" already exists
}}}
Verified with Django (1.9.6, 1.9.12 and 1.10.5) and psycopg2 (2.5.2) on
macOS 10.12.2 with Python 2.7.12, PostgreSQL 9.5.4.
--
Ticket URL: <https://code.djangoproject.com/ticket/27764>
Django <https://code.djangoproject.com/>
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