public static List<FieldNode> mergeFieldNodes(List<FieldNode> left, List<FieldNode> right) {
    List<FieldNode> result = new ArrayList<>(left);
    for (FieldNode fn : right) {
      result = mergeFieldNodes(result, fn);
    }
    return result;
  }
Merge the field node 'fn' into list 'nodes', and return the result list.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/FieldNode.java