private List<String> splitMaps(List<String> mapq) {
      if (null == mapq) {
        return null;
      }
      final List<String> ret = new ArrayList<String>();
      for (String s : mapq) {
        Collections.addAll(ret, s.split(","));
      }
      return ret;
    }
Unregister a specific dag

This method and registerDag must be synchronized externally to prevent races in shuffle token registration/unregistration

@param dir
@param applicationIdString
@param dagIdentifier
llap-server/src/java/org/apache/hadoop/hive/llap/shufflehandler/ShuffleHandler.java