private Set<String> loadHFileRefs(List<TableName> tableList) throws IOException {
    if (connection == null) {
      connection = ConnectionFactory.createConnection(conf);
    }
    try (BackupSystemTable tbl = new BackupSystemTable(connection)) {
      Map<byte[], List<Path>>[] res = tbl.readBulkLoadedFiles(null, tableList);
      secondPrevReadFromBackupTbl = prevReadFromBackupTbl;
      prevReadFromBackupTbl = EnvironmentEdgeManager.currentTime();
      return getFilenameFromBulkLoad(res);
    }
  }
Implementation of a file cleaner that checks if an hfile is still referenced by backup before
deleting it from hfile archive directory.
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/BackupHFileCleaner.java