Remove useless index

app/models/game.rb

@@ -11,8 +11,8 @@ class Game < ApplicationRecord
   attribute :release_date,  :datetime
   attribute :cover_url,     :string
 
-  validates :game_code,   format: { with: GAME_CODE_FORMAT }
   validates :region,      inclusion: { in: REGIONS }
+  validates :game_code,   format: { with: GAME_CODE_FORMAT }, allow_nil: true
   validates :nsuid,       format: { with: NSUID_CODE_FORMAT }, allow_nil: true
 
   has_many :prices

db/migrate/20170606195755_change_game_indexes.rb

@@ -0,0 +1,5 @@
+class ChangeGameIndexes < ActiveRecord::Migration[5.1]
+  def change
+    remove_index :games, column: %i[game_code region], unique: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170520131614) do
+ActiveRecord::Schema.define(version: 20170606195755) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -25,7 +25,6 @@
     t.string "cover_url"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.index ["game_code", "region"], name: "index_games_on_game_code_and_region", unique: true
     t.index ["game_code"], name: "index_games_on_game_code"
     t.index ["nsuid"], name: "index_games_on_nsuid"
   end