@VisibleForTesting
    static int getCurrentThreadPoolSize() {
      synchronized (Context.class) {
        return (threadPool instanceof ThreadPoolExecutor)
            ? ((ThreadPoolExecutor)threadPool).getPoolSize() : ((threadPool == null) ? 0 : -1);
      }
    }
The global information about the split generation that we pass around to
the different worker threads.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcInputFormat.java