Rails migration by sql statement directly

reference: http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

Sometimes you need to do something in SQL not abstracted directly by migrations:

class MakeJoinUnique < ActiveRecord::Migration    

def up      

execute "ALTER TABLE `pages_linked_pages` ADD UNIQUE `page_id_linked_page_id` (`page_id`,`linked_page_id`)"    

end      

def down      

execute "ALTER TABLE `pages_linked_pages` DROP INDEX `page_id_linked_page_id`"    

end  

end