preloader.md

https://github.com/rails/rails/blob/master/activerecord/lib/active_record/associations/preloader.rb#L3 http://stackoverflow.com/questions/1376212/how-to-determine-if-rails-association-is-eager-loaded

ActiveRecord::Associations::Preloader

preload the association data

    ActiveRecord::Associations::Preloader.new(students, [
      {
        :school => [
          :reports,
        ],
      },
      :comments,
    ]).run