records_by_reflection

# File activerecord/lib/active_record/associations/preloader.rb, line 142
      def records_by_reflection(association)
        records.group_by do |record|
          record_class = record.class
          reflection = record_class.reflections[association]

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

          reflection
        end
      end