docs: function (arr, joiner) {
          joiner = joiner || null;
          var args;
          arr = arr.map(function (a) {
              return isInstanceOf(a, Expression, LiteralString, Boolean) || isNull(a) ? a : sql.stringToIdentifier(a);
          });
          if (joiner) {
              var newJoiner = [];
              for (var i = 0; i < arr.length; i++) {
                  newJoiner.push(joiner);
              }
              args = array.flatten(array.zip(arr, newJoiner));
              args.pop();
          } else {
              args = arr;
          }
          args = args.map(function (a) {
              return isInstanceOf(a, Expression, LiteralString, Boolean) || isNull(a) ? a : "" + a;
          });
          return StringExpression.fromArgs(["||"].concat(args));
      }