@Explain(displayName = "DagId")
  public String getDagId() {
    return dagId;
  }
TezWork. This class encapsulates all the work objects that can be executed
in a single tez job. Currently it's basically a tree with MapWork at the
leaves and and ReduceWork in all other nodes.
ql/src/java/org/apache/hadoop/hive/ql/plan/TezWork.java