preprocess_order_args

# File activerecord/lib/active_record/relation/query_methods.rb, line 1117
      def preprocess_order_args(order_args)
        order_args.map! do |arg|
          klass.send(:sanitize_sql_for_order, arg)
        end
        order_args.flatten!
        validate_order_args(order_args)

        references = order_args.grep(String)
        references.map! { |arg| arg =~ /^([a-zA-Z]\w*)\.(\w+)/ && $1 }.compact!
        references!(references) if references.any?

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