public static BaseWork getMergeWork(Configuration jconf) {
    String currentMergePrefix = jconf.get(DagUtils.TEZ_MERGE_CURRENT_MERGE_FILE_PREFIX);
    if (StringUtils.isEmpty(currentMergePrefix)) {
      return null;
    }
    return getMergeWork(jconf, jconf.get(DagUtils.TEZ_MERGE_CURRENT_MERGE_FILE_PREFIX));
  }
ReduceField:
KEY: record key
VALUE: record value
ql/src/java/org/apache/hadoop/hive/ql/exec/Utilities.java