#27764: Running migration that deletes child model (in multi-table inheritance)
backwards results in an error
-------------------------------------+-------------------------------------
Reporter: Alexandru | Owner: nobody
Mărășteanu |
Type: Bug | Status: new
Component: Migrations | Version: 1.10
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Alexandru Mărășteanu:
Old description:
> 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
> {{{
> $ python manage.py migrate foo zero
> Operations to perform:
> Unapply all migrations: foo
> Running migrations:
> Rendering model states... DONE
> Unapplying foo.0002_auto_20170123_1212...Traceback (most recent call
> last):
> File "manage.py", line 10, in <module>
> execute_from_command_line(sys.argv)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/core/management/__init__.py", line 367, in
> execute_from_command_line
> utility.execute()
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/core/management/__init__.py", line 359, in execute
> self.fetch_command(subcommand).run_from_argv(self.argv)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/core/management/base.py", line 294, in run_from_argv
> self.execute(*args, **cmd_options)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/core/management/base.py", line 345, in execute
> output = self.handle(*args, **options)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/core/management/commands/migrate.py", line 204, in handle
> fake_initial=fake_initial,
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/migrations/executor.py", line 119, in migrate
> state = self._migrate_all_backwards(plan, full_plan, fake=fake)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/migrations/executor.py", line 194, in
> _migrate_all_backwards
> self.unapply_migration(states[migration], migration, fake=fake)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/migrations/executor.py", line 264, in
> unapply_migration
> state = migration.unapply(state, schema_editor)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/migrations/migration.py", line 178, in unapply
> operation.database_backwards(self.app_label, schema_editor,
> from_state, to_state)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/migrations/operations/fields.py", line 153, in
> database_backwards
> schema_editor.add_field(from_model,
> to_model._meta.get_field(self.name))
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/postgresql/schema.py", line 21, in add_field
> super(DatabaseSchemaEditor, self).add_field(model, field)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/base/schema.py", line 409, in add_field
> self.execute(sql, params)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/base/schema.py", line 112, in execute
> cursor.execute(sql, params)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/utils.py", line 79, in execute
> return super(CursorDebugWrapper, self).execute(sql, params)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/utils.py", line 64, in execute
> return self.cursor.execute(sql, params)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/utils.py", line 94, in __exit__
> six.reraise(dj_exc_type, dj_exc_value, traceback)
> File "/Users/alexei/.virtualenvs/djbug/lib/python2.7/site-
> packages/django/db/backends/utils.py", line 64, in execute
> return self.cursor.execute(sql, params)
> 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.
New description:
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
{{{
$ python manage.py migrate foo zero
Operations to perform:
Unapply all migrations: foo
Running migrations:
Rendering model states... DONE
Unapplying foo.0002_auto_20170123_1212...Traceback (most recent call
last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/djbug/lib/python2.7/site-
packages/django/core/management/__init__.py", line 367, in
execute_from_command_line
utility.execute()
File "/djbug/lib/python2.7/site-
packages/django/core/management/__init__.py", line 359, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/djbug/lib/python2.7/site-
packages/django/core/management/base.py", line 294, in run_from_argv
self.execute(*args, **cmd_options)
File "/djbug/lib/python2.7/site-
packages/django/core/management/base.py", line 345, in execute
output = self.handle(*args, **options)
File "/djbug/lib/python2.7/site-
packages/django/core/management/commands/migrate.py", line 204, in handle
fake_initial=fake_initial,
File "/djbug/lib/python2.7/site-
packages/django/db/migrations/executor.py", line 119, in migrate
state = self._migrate_all_backwards(plan, full_plan, fake=fake)
File "/djbug/lib/python2.7/site-
packages/django/db/migrations/executor.py", line 194, in
_migrate_all_backwards
self.unapply_migration(states[migration], migration, fake=fake)
File "/djbug/lib/python2.7/site-
packages/django/db/migrations/executor.py", line 264, in unapply_migration
state = migration.unapply(state, schema_editor)
File "/djbug/lib/python2.7/site-
packages/django/db/migrations/migration.py", line 178, in unapply
operation.database_backwards(self.app_label, schema_editor,
from_state, to_state)
File "/djbug/lib/python2.7/site-
packages/django/db/migrations/operations/fields.py", line 153, in
database_backwards
schema_editor.add_field(from_model,
to_model._meta.get_field(self.name))
File "/djbug/lib/python2.7/site-
packages/django/db/backends/postgresql/schema.py", line 21, in add_field
super(DatabaseSchemaEditor, self).add_field(model, field)
File "/djbug/lib/python2.7/site-
packages/django/db/backends/base/schema.py", line 409, in add_field
self.execute(sql, params)
File "/djbug/lib/python2.7/site-
packages/django/db/backends/base/schema.py", line 112, in execute
cursor.execute(sql, params)
File "/djbug/lib/python2.7/site-packages/django/db/backends/utils.py",
line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/djbug/lib/python2.7/site-packages/django/db/backends/utils.py",
line 64, in execute
return self.cursor.execute(sql, params)
File "/djbug/lib/python2.7/site-packages/django/db/utils.py", line 94,
in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/djbug/lib/python2.7/site-packages/django/db/backends/utils.py",
line 64, in execute
return self.cursor.execute(sql, params)
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#comment:2>
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