id summary reporter owner description type status component version severity resolution keywords cc stage has_patch needs_docs needs_tests needs_better_patch easy ui_ux 27746 Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL David CHANIAL nobody "== Context * I'm not observing this bug when not using '''multi-table inheritance'''. * I'm using '''MySQL''' (''MariaDB-10.0''), and i don't know if the bug happen with another database backend or server. * In an existing project named '''bobb''' * A similary bug exist with empty child models too, like '''Account''' or '''Device''' == Prepare the bug {{{ python manage.py startapp buggymigration echo ""INSTALLED_APPS = tuple(list(INSTALLED_APPS) + ['buggymigration'])"" >> bobb/settings.py # creating models using multi-table in heritance in buggymigration # by making changes to buggymigration/models.py cat buggymigration/models.py }}} {{{ #!python from __future__ import unicode_literals from django.db import models class UniqueSerialNumber(models.Model): pass class Account(UniqueSerialNumber): pass class Device(UniqueSerialNumber): pass class Contract(UniqueSerialNumber): customer = models.ForeignKey('Account') machine = models.ForeignKey('Device') }}} {{{ python manage.py makemigrations }}} {{{ Migrations for 'buggymigration': 0001_initial.py: - Create model UniqueSerialNumber - Create model Account - Create model Contract - Create model Device - Add field machine to contract }}} {{{ python manage.py migrate }}} {{{ Operations to perform: Apply all migrations: sessions, admin, auth, buggymigration, contenttypes Running migrations: Applying buggymigration.0001_initial... OK }}} == Trigger the bug {{{ # trying to remove the model Contract # by editing buggymigration/models.py and commenting the model cat buggymigration/models.py }}} {{{ #!python from __future__ import unicode_literals from django.db import models class UniqueSerialNumber(models.Model): pass class Account(UniqueSerialNumber): pass class Device(UniqueSerialNumber): pass ''' class Contract(UniqueSerialNumber): customer = models.ForeignKey('Account') machine = models.ForeignKey('Device') ''' }}} {{{ python manage.py makemigrations }}} {{{ Migrations for 'buggymigration': 0002_auto_20170118_1258.py: - Remove field customer from contract - Remove field machine from contract - Remove field uniqueserialnumber_ptr from contract - Delete model Contract }}} {{{ cat buggymigration/migrations/0002_auto_20170118_1258.py }}} {{{ #!python # -*- coding: utf-8 -*- # Generated by Django 1.9.12 on 2017-01-18 11:58 from __future__ import unicode_literals from django.db import migrations class Migration(migrations.Migration): dependencies = [ ('buggymigration', '0001_initial'), ] operations = [ migrations.RemoveField( model_name='contract', name='customer', ), migrations.RemoveField( model_name='contract', name='machine', ), migrations.RemoveField( model_name='contract', name='uniqueserialnumber_ptr', ), migrations.DeleteModel( name='Contract', ), ] }}} {{{ python manage.py sqlmigrate buggymigration 0002_auto_20170118_1258 }}} {{{ #!sql BEGIN; -- -- Remove field customer from contract -- ALTER TABLE `buggymigration_contract` DROP FOREIGN KEY `D5e39daefe3dcc06188b9ecc2ad1e28a`; ALTER TABLE `buggymigration_contract` DROP COLUMN `customer_id` CASCADE; -- -- Remove field machine from contract -- ALTER TABLE `buggymigration_contract` DROP FOREIGN KEY `a46c0a1038d68a3574efaf2d757512fd`; ALTER TABLE `buggymigration_contract` DROP COLUMN `machine_id` CASCADE; -- -- Remove field uniqueserialnumber_ptr from contract -- ALTER TABLE `buggymigration_contract` DROP FOREIGN KEY `f406fa7acbef3134feeae510d6e9affd`; ALTER TABLE `buggymigration_contract` DROP COLUMN `uniqueserialnumber_ptr_id` CASCADE; -- -- Delete model Contract -- DROP TABLE `buggymigration_contract` CASCADE; COMMIT; }}} == The bug {{{ python manage.py migrate buggymigration }}} {{{ Operations to perform: Apply all migrations: buggymigration Running migrations: Applying buggymigration.0002_auto_20170118_1258...Traceback (most recent call last): File ""manage.py"", line 10, in execute_from_command_line(sys.argv) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 353, in execute_from_command_line utility.execute() File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py"", line 345, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py"", line 348, in run_from_argv self.execute(*args, **cmd_options) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py"", line 399, in execute output = self.handle(*args, **options) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py"", line 200, in handle executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 92, in migrate self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 121, in _migrate_all_forwards state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/migrations/executor.py"", line 198, in apply_migration state = migration.apply(state, schema_editor) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/migrations/migration.py"", line 123, in apply operation.database_forwards(self.app_label, schema_editor, old_state, project_state) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py"", line 121, in database_forwards schema_editor.remove_field(from_model, from_model._meta.get_field(self.name)) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/base/schema.py"", line 438, in remove_field self.execute(sql) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/base/schema.py"", line 110, in execute cursor.execute(sql, params) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 79, in execute return super(CursorDebugWrapper, self).execute(sql, params) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 64, in execute return self.cursor.execute(sql, params) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/utils.py"", line 95, in __exit__ six.reraise(dj_exc_type, dj_exc_value, traceback) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py"", line 64, in execute return self.cursor.execute(sql, params) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py"", line 112, in execute return self.cursor.execute(query, args) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/MySQLdb/cursors.py"", line 205, in execute self.errorhandler(self, exc, value) File ""/home/backoffice/virtualenv/local/lib/python2.7/site-packages/MySQLdb/connections.py"", line 36, in defaulterrorhandler raise errorclass, errorvalue django.db.utils.OperationalError: (1090, ""You can't delete all columns with ALTER TABLE; use DROP TABLE instead"") }}} " Bug new Migrations dev Normal Accepted 0 0 0 0 0 0