discourse/db/migrate/20120503205521_add_site_id_to_users.rb

class AddSiteIdToUsers < ActiveRecord::Migration
  def change
    add_column :users, :site_id, :integer
    add_column :users, :bio, :text

    add_index :users, :site_id
    execute "UPDATE users SET site_id = 1"    
  end
end