instance method preprocess_order_args

# File activerecord/lib/active_record/relation/query_methods.rb, line 1393
      def preprocess_order_args(order_args)
        @klass.disallow_raw_sql!(
          order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a },
          permit: connection.column_name_with_order_matcher
        )

        validate_order_args(order_args)

        references = column_references(order_args)
        self.references_values |= references unless references.empty?

        # if a symbol is given we prepend the quoted table name
        order_args.map! do |arg|
          case arg
          when Symbol
            order_column(arg.to_s).asc
          when Hash
            arg.map { |field, dir|
              case field
              when Arel::Nodes::SqlLiteral
                field.public_send(dir.downcase)
              else
                order_column(field.to_s).public_send(dir.downcase)
              end
            }
          else
            arg
          end
        end.flatten!
      end