fix migration to remove original stupid index hopefully

db/migrate/012_add_user_preference_id.rb

@@ -1,7 +1,7 @@
 class AddUserPreferenceId < ActiveRecord::Migration
   def self.up
+    remove_index 'user_preferences', ['id', 'k']
     add_column "user_preferences", "id", :bigint, :limit => 64, :null => false, :options => "AUTO_INCREMENT"
-    
     add_index "user_preferences", ["id"], :name => "user_preferences_id_idx"
   end