docs: function (args) {
              args = argsToArray(arguments);
              if (args.length && !this.supportsDistinctOn) {
                  throw new QueryError("DISTICT ON is not supported");
              }
              args = args.map(function (a) {
                  return isString(a) ? new Identifier(a) : a;
              });
              return this.mergeOptions({distinct: args});
          }