Cannot drop index that was created when the table was created.

[tapocol@…]

To reproduce with MySQL:

• Make a model with a field that has db_index: True
• Generate migration with --initial
• Run Migration
• Remove db_index: True from field settings.
• Generate migration with --auto
• Run Migration to see the error.

db_create_index and db_create_table with a field that has the setting 'db_index' seem to create two different naming styles for the index. db_delete_index uses the naming style used by db_create_index. So, when it is trying to delete the index that was created in db_create_table, MySQL returns the error message "Can't DROP 'xxx_xxx'; check that column/key exists".

[Petri Lehtinen <petri@…>]

This affects me too. I have a foreign key and would like to remove its index.

./manage.py shemamigration app --auto generates a call like db.delete_index('app_model', ['field_id']) which, when applied, tries to delete the index app_table_field_id. In the database, the index's actual name is app_table_hexstr, so there are two different naming styles indeed.

[thasonic@…]

I've made the patch and created the pull request: ​https://bitbucket.org/andrewgodwin/south/pull-request/34/fixed-issue-776