@Override
    public long[] putFileData(Object fileKey, DiskRange[] ranges,
        MemoryBuffer[] data, long baseOffset, CacheTag tag) {
      if (data != null) {
        return lowLevelCache.putFileData(
            fileKey, ranges, data, baseOffset, Priority.NORMAL, counters, tag);
      } else if (metadataCache != null) {
        metadataCache.putIncompleteCbs(fileKey, ranges, baseOffset, isStopped);
      }
      return null;
    }
A reference to parent DataReader not owned by this object.
llap-server/src/java/org/apache/hadoop/hive/llap/io/encoded/OrcEncodedDataReader.java