private void closeOffsetReader() {
      if (offsetReader == null) return;
      try {
        offsetReader.close();
      } catch (Exception ex) {
        LlapIoImpl.LOG.error("Failed to close source reader", ex);
      }
      offsetReader = null;
    }
This class only exists because Java doesn't have yield return. The original method
before this change only needed yield return-s sprinkled here and there; however,
Java developers are usually paid by class, so here we go.
llap-server/src/java/org/apache/hadoop/hive/llap/io/encoded/SerDeEncodedDataReader.java