Migrate command error in Django - django

Question

I am getting a migrate command error --
django.db.utils.OperationalError: (1170, "BLOB/TEXT column 'module_name' used in key specification without a key length")
The model is
class Coupling(models.Model):
coupling_name = models.CharField(max_length=150, blank=False, default=True, unique=True)
module_name = models.TextField(max_length=255)
There is a key length though.
Traceback (most recent call last):
File "manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\core\management\__init__.py", line 367, in execute_from_command_line
utility.execute()
File "C:\virtualenvs\ciasenv\lib\site-packages\django\core\management\__init__.py", line 359, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\core\management\base.py", line 294, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\core\management\base.py", line 345, in execute
output = self.handle(*args, **options)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\core\management\commands\migrate.py", line 204, in handle
fake_initial=fake_initial,
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\migrations\executor.py", line 115, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\migrations\executor.py", line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\migrations\migration.py", line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\migrations\operations\fields.py", line 204, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\base\schema.py", line 495, in alter_field
old_db_params, new_db_params, strict)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\base\schema.py", line 678, in _alter_field
self.execute(self._create_unique_sql(model, [new_field.column]))
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\base\schema.py", line 112, in execute
cursor.execute(sql, params)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\utils\six.py", line 685, in reraise
raise value.with_traceback(tb)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\virtualenvs\ciasenv\lib\site-packages\django\db\backends\mysql\base.py", line 112, in execute
return self.cursor.execute(query, args)
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\cursors.py", line 250, in execute
self.errorhandler(self, exc, value)
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\connections.py", line 50, in defaulterrorhandler
raise errorvalue
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\cursors.py", line 247, in execute
res = self._query(query)
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\cursors.py", line 411, in _query
rowcount = self._do_query(q)
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\cursors.py", line 374, in _do_query
db.query(q)
File "C:\virtualenvs\ciasenv\lib\site-packages\MySQLdb\connections.py", line 292, in query
_mysql.connection.query(self, query)
django.db.utils.OperationalError: (1061, "Duplicate key name 'accounts_coupling_coupling_name_175325e1_uniq'")
Any help is highly appreciated. Thanks in advance.

Answer 1

The first error might be because you tried to set unique=True for the TextField. This is not possible for MySQL, as noted in the docs.
The second error is because you are trying to create an index that already exists. This could be because you already ran the migration and it failed part way through. MySQL does not run schema changes in a transaction, so changes aren't rolled back if they fail. You could try dropping the index manually, or, if this is a new project, it might be easier to drop the database and start again.