Column type and index not support by Django ORM - best way to alter/add them

[graeme]

I need to do the the following to Postgres tables for Django models:

1) Add a functional index

2) Have a bigserial primary key and a bigint foreign key point to it.

Given that I only want this on a single install, is there any reason not to just do it directly? I have found code snippets with "AutoBigInt" fields, but only one claims to support South and non mention Django migrations. I have not found anything to help with adding the index.

The best I can come up with is to directly alter the column type, and do the same to add the index, and write a migration to do that later IF we ever need more than one install - otherwise its more work that way.

Given that the primary key and the foreign keys pointing to it are unlikely to ever change, can I also guess that this is not likely to cause problems with migrations (South and the new Djnago ones in 1.7 when we upgrade) that change other fields of the model?