private static List<FieldNode> getNestedColPathByDesc(ExprNodeDesc desc) {
    List<FieldNode> res = new ArrayList<>();
    getNestedColsFromExprNodeDesc(desc, null, res);
    return mergeFieldNodes(new ArrayList<FieldNode>(), res);
  }
Given the 'desc', construct a list of field nodes representing the
nested columns paths referenced by this 'desc'.
@param desc the node descriptor
@return a list of nested column paths referenced in the 'desc'
ql/src/java/org/apache/hadoop/hive/ql/optimizer/ColumnPrunerProcCtx.java