records_by_reflection

# File activerecord/lib/active_record/associations/preloader.rb, line 141
      def records_by_reflection(association)
        records.group_by do |record|
          reflection = record.class.reflections[association]

          unless reflection
            raise ActiveRecord::ConfigurationError, "Association named '#{association}' was not found; "                                                      "perhaps you misspelled it?"
          end

          reflection
        end
      end