Specify custom primary key in migration

Question

I have a data structure:

  t.integer :userID
  t.string :apikey
  t.integer :characterID

The userID should be the primary key (name is not

Answer 1

Instead of circumventing the ActiveRecord model, I made userID a normal column and used

validates_uniqueness_of :userID, :message => "userID needs to be unique"

on the model to validate it.