@Override
  public OptionalLong getBulkLoadTimestamp() {
    byte[] bulkLoadTimestamp = metadataMap.get(BULKLOAD_TIME_KEY);
    return bulkLoadTimestamp == null
      ? OptionalLong.empty()
      : OptionalLong.of(Bytes.toLong(bulkLoadTimestamp));
  }
Returns true if the file is still used in reads
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HStoreFile.java