@Override
  public void shutdown() {
    super.shutdown();
    if (executor != null) {
      executor.destroy();
      executor = null;
    }
  }
MapredLocalTask represents any local work (i.e.: client side work) that hive needs to
execute. E.g.: This is used for generating Hashtables for Mapjoins on the client
before the Join is executed on the cluster.

MapRedLocalTask does not actually execute the work in process, but rather generates
a command using ExecDriver. ExecDriver is what will finally drive processing the records.
ql/src/java/org/apache/hadoop/hive/ql/exec/mr/MapredLocalTask.java