@Override
    public boolean equals(Object obj)
    {
      if (this == obj) {
        return true;
      }
      if (!super.equals(obj)) {
        return false;
      }
      if (getClass() != obj.getClass()) {
        return false;
      }
      OrderExpression other = (OrderExpression) obj;
      if (order != other.order) {
        return false;
      }
      if (nullOrder != other.nullOrder) {
        return false;
      }
      return true;
    }
Add order expressions from the list of expressions in the format of ASTNode
@param nodes
ql/src/java/org/apache/hadoop/hive/ql/parse/PTFInvocationSpec.java