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up vote 5 down vote favorite

I am trying to add indexes on model fields using Field.db_index for an app that has migrations. Looking at Django's documentation all I need to do is to set db_index=True:

class Person(models.Model):
    first_name = models.CharField()
    last_name = models.CharField(db_index=True)

and then I first tried the new Django's Migration:

./manage.py makemigrations app-name

but Migration does not seem to notice the change and does not add the sql command for creating an index. So I tried django-admin.py as explained here:

django-admin.py sqlindexes app-name

But that does not print the sql command either and it exits with the following error:

CommandError: App 'app-name' has migrations. Only the sqlmigrate and sqlflush commands can be used when an app has migrations.
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up vote 4 down vote accepted

OK, I managed to create the indexes using Meta.index_together. It is not the cleanest way, since I am not actually indexing multiple fields together but it works with makemigrations:

class Person(models.Model):
    class Meta():
        index_together = [['last_name']]
    first_name = models.CharField()
    last_name = models.CharField()

Now makemigrations does make a new migration:

./manage.py makemigrations app-name

>>Migrations for 'app-name':
>>  0005_auto_20140929_1540.py:
>>    - Alter index_together for Person (1 constraint(s))

And the corresponding sql command is actually CREATE INDEX.

./manage.py sqlmigrate app-name 0005_auto_20140929_1540

>>BEGIN;
>>CREATE INDEX app-name_person_last_name_7...4_idx ON `app-name_person` (`last_name`);
>>COMMIT;
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