@VisibleForTesting
  void startWorkers() {
    for (int i = 0; i < workers.length; ++i) {
      LOG.info("Stats updater worker thread " + workers[i].getName() + " started");
      workers[i].start();
    }
  }
Whether to only update stats that already exist and are out of date.
ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUpdaterThread.java