Create missing auto increment attribute with rails migration

Question

I\'m writing a migration to convert a non-rails app into the right format for rails - one of the tables for some reason does not have auto increment set on the id column. I

Answer 1

The Postgres answer by @jlfenaux misses out on the serial type, which does all of it for you automatically:

ALTER TABLE tbl add tbl_id serial;

More details in this related answer.