code: @Description("concatenates given character strings")
      @ScalarFunction
      @LiteralParameters({"x", "y", "u"})
      @Constraint(variable = "u", expression = "x + y")
      @SqlType("char(u)")
      public static Slice concat(@LiteralParameter("x") Long x, @SqlType("char(x)") Slice left, @SqlType("char(y)") Slice right)
      {
          int rightLength = right.length();
          if (rightLength == 0) {
              return left;
          }
  
          Slice paddedLeft = padSpaces(left, x.intValue());
          int leftLength = paddedLeft.length();
  
          Slice result = Slices.allocate(leftLength + rightLength);
          result.setBytes(0, paddedLeft);
          result.setBytes(leftLength, right);
  
          return result;
      }
docs: TODO: implement N arguments char concat