# File lib/origin/optional.rb, line 170
    def order_by(*spec)
      option(spec) do |options, query|
        spec.compact.each do |criterion|
          criterion.__sort_option__.each_pair do |field, direction|
            add_sort_option(options, field, direction)
          end
          query.pipeline.push("$sort" => options[:sort]) if aggregating?
        end
      end
    end