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 31503 Moving a unique constraint from unique_together to Field.unique generate an invalid migration. Xiang Wang David Wobrock "You can see a demo example to show the bug at [github](https://github.com/ramwin/testunique/). I met a problem when I convert a `unique_together` to the `unique=True` attribute. first commit, everything is ok I create a model file. {{{ // testapp/models.py class MyModel(models.Model): name = models.CharField(max_length=32) class Meta: unique_together = (""name"", ) }}} the migrations file looks like this. {{{ // testapp/migrations/0001_initial.py # Generated by Django 3.0.5 on 2020-04-22 12:47 from django.db import migrations, models class Migration(migrations.Migration): dependencies = [ ('testapp', '0001_initial'), ] operations = [ migrations.AlterField( model_name='mymodel', name='name', field=models.CharField(max_length=32, unique=True), ), migrations.AlterUniqueTogether( name='mymodel', unique_together=set(), ), ] }}} second commit: then I remove the unique_together and add unique=True to the field MyModel.name {{{ model file class MyModel(models.Model): name = models.CharField(max_length=32, unique=True) class Meta: pass # unique_together = (""name"", ) 0002 migrations file class Migration(migrations.Migration): dependencies = [ ('testapp', '0001_initial'), ] operations = [ migrations.AlterField( model_name='mymodel', name='name', field=models.CharField(max_length=32, unique=True), ), migrations.AlterUniqueTogether( name='mymodel', unique_together=set(), ), ] }}} However, when I apply the migrations, an error occurs; {{{ wangx@aliyun:~/testunique$ python3 manage.py migrate Operations to perform: Apply all migrations: admin, auth, contenttypes, sessions, testapp Running migrations: Applying contenttypes.0001_initial... OK Applying auth.0001_initial... OK Applying admin.0001_initial... OK Applying admin.0002_logentry_remove_auto_add... OK Applying admin.0003_logentry_add_action_flag_choices... OK Applying contenttypes.0002_remove_content_type_name... OK Applying auth.0002_alter_permission_name_max_length... OK Applying auth.0003_alter_user_email_max_length... OK Applying auth.0004_alter_user_username_opts... OK Applying auth.0005_alter_user_last_login_null... OK Applying auth.0006_require_contenttypes_0002... OK Applying auth.0007_alter_validators_add_error_messages... OK Applying auth.0008_alter_user_username_max_length... OK Applying auth.0009_alter_user_last_name_max_length... OK Applying auth.0010_alter_group_name_max_length... OK Applying auth.0011_update_proxy_permissions... OK Applying sessions.0001_initial... OK Applying testapp.0001_initial... OK Applying testapp.0002_auto_20200422_1247...Traceback (most recent call last): File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 86, in _execute return self.cursor.execute(sql, params) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/mysql/base.py"", line 74, in execute return self.cursor.execute(query, args) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/cursors.py"", line 209, in execute res = self._query(query) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/cursors.py"", line 315, in _query db.query(q) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/connections.py"", line 239, in query _mysql.connection.query(self, query) MySQLdb._exceptions.OperationalError: (1061, ""Duplicate key name 'testapp_mymodel_name_ba5e2bd2_uniq'"") The above exception was the direct cause of the following exception: Traceback (most recent call last): File ""manage.py"", line 21, in main() File ""manage.py"", line 17, in main execute_from_command_line(sys.argv) File ""/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py"", line 401, in execute_from_command_line utility.execute() File ""/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py"", line 395, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File ""/usr/local/lib/python3.6/dist-packages/django/core/management/base.py"", line 328, in run_from_argv self.execute(*args, **cmd_options) File ""/usr/local/lib/python3.6/dist-packages/django/core/management/base.py"", line 369, in execute output = self.handle(*args, **options) File ""/usr/local/lib/python3.6/dist-packages/django/core/management/base.py"", line 83, in wrapped res = handle_func(*args, **kwargs) File ""/usr/local/lib/python3.6/dist-packages/django/core/management/commands/migrate.py"", line 233, in handle fake_initial=fake_initial, File ""/usr/local/lib/python3.6/dist-packages/django/db/migrations/executor.py"", line 117, in migrate state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial) File ""/usr/local/lib/python3.6/dist-packages/django/db/migrations/executor.py"", line 147, in _migrate_all_forwards state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial) File ""/usr/local/lib/python3.6/dist-packages/django/db/migrations/executor.py"", line 245, in apply_migration state = migration.apply(state, schema_editor) File ""/usr/local/lib/python3.6/dist-packages/django/db/migrations/migration.py"", line 124, in apply operation.database_forwards(self.app_label, schema_editor, old_state, project_state) File ""/usr/local/lib/python3.6/dist-packages/django/db/migrations/operations/fields.py"", line 249, in database_forwards schema_editor.alter_field(from_model, from_field, to_field) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/base/schema.py"", line 565, in alter_field old_db_params, new_db_params, strict) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/base/schema.py"", line 745, in _alter_field self.execute(self._create_unique_sql(model, [new_field.column])) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/base/schema.py"", line 142, in execute cursor.execute(sql, params) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 100, in execute return super().execute(sql, params) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 68, in execute return self._execute_with_wrappers(sql, params, many=False, executor=self._execute) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 77, in _execute_with_wrappers return executor(sql, params, many, context) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 86, in _execute return self.cursor.execute(sql, params) File ""/usr/local/lib/python3.6/dist-packages/django/db/utils.py"", line 90, in __exit__ raise dj_exc_value.with_traceback(traceback) from exc_value File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py"", line 86, in _execute return self.cursor.execute(sql, params) File ""/usr/local/lib/python3.6/dist-packages/django/db/backends/mysql/base.py"", line 74, in execute return self.cursor.execute(query, args) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/cursors.py"", line 209, in execute res = self._query(query) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/cursors.py"", line 315, in _query db.query(q) File ""/usr/local/lib/python3.6/dist-packages/MySQLdb/connections.py"", line 239, in query _mysql.connection.query(self, query) django.db.utils.OperationalError: (1061, ""Duplicate key name 'testapp_mymodel_name_ba5e2bd2_uniq'"") }}} I check the sql for these migrations, it shows: {{{ wangx@aliyun:~/testunique$ python3 manage.py sqlmigrate testapp 0001 -- -- Create model MyModel -- CREATE TABLE `testapp_mymodel` (`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `name` varchar(32) NOT NULL); ALTER TABLE `testapp_mymodel` ADD CONSTRAINT `testapp_mymodel_name_ba5e2bd2_uniq` UNIQUE (`name`); wangx@aliyun:~/testunique$ python3 manage.py sqlmigrate testapp 0002 -- -- Alter field name on mymodel -- ALTER TABLE `testapp_mymodel` ADD CONSTRAINT `testapp_mymodel_name_ba5e2bd2_uniq` UNIQUE (`name`); -- -- Alter unique_together for mymodel (0 constraint(s)) -- ALTER TABLE `testapp_mymodel` DROP INDEX `testapp_mymodel_name_ba5e2bd2_uniq`; }}} it looks like django will * first create the index for unique=True * second drop the index for unique_together=('name', ) but the program for creating index name generates the same index name :testapp_mymodel_name_ba5e2bd2_uniq, so when django create the same index, Duplicate key name error occurs." Bug closed Migrations 3.0 Normal fixed unique_together unique migrations ramwin@… David Wobrock Ready for checkin 1 0 0 0 0 0