Add an index for Note#updated_at

db/migrate/20140428105831_add_notes_index_updated_at.rb

+class AddNotesIndexUpdatedAt < ActiveRecord::Migration
+  def change
+    add_index :notes, :updated_at
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20140416185734) do
+ActiveRecord::Schema.define(version: 20140428105831) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -200,6 +200,7 @@ ActiveRecord::Schema.define(version: 20140416185734) do
   add_index "notes", ["noteable_type"], name: "index_notes_on_noteable_type", using: :btree
   add_index "notes", ["project_id", "noteable_type"], name: "index_notes_on_project_id_and_noteable_type", using: :btree
   add_index "notes", ["project_id"], name: "index_notes_on_project_id", using: :btree
+  add_index "notes", ["updated_at"], name: "index_notes_on_updated_at", using: :btree
 
   create_table "projects", force: true do |t|
     t.string   "name"