Dado que IF EXISTS no es compatible con la indexación de MySQL, es posible que desee escribir su propia migración:

 def drop_index_if_exists(apps, schema_editor): # access to the connection since schema_editor.execute does not return the cursor with schema_editor.connection.cursor() as cursor: cursor.execute("SHOW INDEX FROM table_name WHERE KEY_NAME = 'index_name'"); exists = int(cursor.fetchone()) > 0 # outside with to close the cursor if exists: schema_editor.execute("CREATE INDEX index_name ON ...") operations = [ migrations.RunPython(drop_index_if_exists) ]

Para mantener la coherencia, puede escribir un método create_index_if_not_exists para cancelar la aplicación de la migración y llamarlo:

 migrations.RunPython(drop_index_if_exists, create_index_if_not_exists)

Aquí hay una solución, gracias por la idea @alfonso.kim

 # -*- coding: utf-8 -*- from __future__ import unicode_literals from django.db import migrations def drop_index_if_exists_and_create(apps, schema_editor): # access to the connection since schema_editor.execute does not return the cursor with schema_editor.connection.cursor() as cursor: cursor.execute("SHOW INDEX FROM table_name WHERE KEY_NAME = 'index_name'") exists = True if cursor.fetchone() else False # outside with to close the cursor if exists: schema_editor.execute("DROP INDEX index_name ON table_name") schema_editor.execute("CREATE INDEX index_name ON table_name(index_name(191))") class Migration(migrations.Migration): dependencies = [ ('table_name', ''), ] operations = [ migrations.RunPython(drop_index_if_exists_and_create) ]

Recibo un error de transacción después de ejecutar su código:

 django.db.transaction.TransactionManagementError: Executing DDL statements while in a transaction on databases that can't perform a rollback is prohibited.

Django 2.5 MySQL 5.7