Migrate command does not create index with operator class for CharField

[Federico Frenguelli]

./manage.py migrate command does not create an additional index with the operator class for a CharField, when db_index=True is added to an existing field.

I created a sample project to reproduce the error here: ​https://github.com/synasius/foo

There are two models, Person and Car.
Person's "name" field was migrated with db_index=True and if I run ./manage.py sqlmigrate bar 0001 I can see both the indexes, one using the operator class varchar_pattern_ops.

The issue occurs when db_index=True is added to Car's name field and then a migration is created. When I run ./manage.py sqlmigrate bar 0002 I can only see one plain index.

I reproduced the issue in Django 1.7.x, 1.8.x and master. I'm using postgresql 9.4.4.

[Simon Charette]

Thanks to the provided sample project I managed to reproduce.

Looks like someone commented on a related ticket to report this inconsistency.

Another oddity is the fact the default non-unique index created has a name ending with _uniq which looks quite suspicious.

[Federico Frenguelli]

Pull request here: ​https://github.com/django/django/pull/5603

[Simon Charette]

Left some comments on the patch.

[Simon Charette]

All comments have been addressed.

[Tim Graham <timograham@…>]

In 3a36c807:

Fixed #25412 -- Fixed missing PostgreSQL index on Char/TextField when using AlterField.

Thanks to Emanuele Palazzetti for the help.

[Tim Graham <timograham@…>]

In 722fae4b:

[1.9.x] Fixed #25412 -- Fixed missing PostgreSQL index on Char/TextField when using AlterField.

Thanks to Emanuele Palazzetti for the help.

Backport of 3a36c8079544c83dcdea4e52181efcd2d1e86b9c from master

[Tim Graham <timograham@…>]

In 905e94a0:

[1.8.x] Fixed #25412 -- Fixed missing PostgreSQL index on Char/TextField when using AlterField.

Thanks to Emanuele Palazzetti for the help.

Backport of 3a36c8079544c83dcdea4e52181efcd2d1e86b9c from master