column_references

# File activerecord/lib/active_record/relation/query_methods.rb, line 1604
      def column_references(order_args)
        references = order_args.flat_map do |arg|
          case arg
          when String, Symbol
            arg
          when Hash
            arg.keys
          end
        end
        references.map! { |arg| arg =~ /^\W?(\w+)\W?\./ && $1 }.compact!
        references
      end