code: protected OrderByElement cloneOrderByElement(OrderByElement orig, Expression expression) {
          OrderByElement element = new OrderByElement();
          element.setAsc(orig.isAsc());
          element.setAscDescPresent(orig.isAscDescPresent());
          element.setNullOrdering(orig.getNullOrdering());
          element.setExpression(expression);
          return element;
      }
docs: 复制 OrderByElement
  
  @param orig       原 OrderByElement
  @param expression 新 OrderByElement 的排序要素
  @return 复制的新 OrderByElement