# File lib/dm-core/query/sort.rb, line 18
      def <=>(other)
        other_value = other.value

        cmp = case
          when @value.nil? && other_value.nil?
            0
          when @value.nil?
            1
          when other_value.nil?
            -1
          else
            @value <=> other_value
        end

        @ascending ? cmp : cmp * -1
      end