Add index on Files

db/migrate/20150421074734_add_file_index_to_files.rb

@@ -0,0 +1,5 @@
+class AddFileIndexToFiles < ActiveRecord::Migration
+  def change
+    add_index(:files, [:context_id, :context_type])
+  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: 20150408155923) do
+ActiveRecord::Schema.define(version: 20150421074734) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -123,6 +123,8 @@ ActiveRecord::Schema.define(version: 20150408155923) do
     t.string   "path"
   end
 
+  add_index "files", ["context_id", "context_type"], name: "index_files_on_context_id_and_context_type", using: :btree
+
   create_table "hints", force: true do |t|
     t.integer  "execution_environment_id"
     t.string   "locale"