run_code_messages添加索引提高查询速度

db/migrate/20190708062910_add_index_for_run_code_message.rb

@@ -0,0 +1,5 @@
+class AddIndexForRunCodeMessage < ActiveRecord::Migration[5.2]
+  def change
+    add_index :run_code_messages, :game_id
+  end
+end