public static void getExprNodeColumnDesc(List<ExprNodeDesc> exprDescList,
      Multimap<Integer, ExprNodeColumnDesc> hashCodeTocolumnDescMap) {
    for (ExprNodeDesc exprNodeDesc : exprDescList) {
      getExprNodeColumnDesc(exprNodeDesc, hashCodeTocolumnDescMap);
    }
  }
Extract fields from the given {@link ExprNodeFieldDesc node descriptor}
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeDescUtils.java