public List<TsFileResource> getUnseqFiles() {
    return unseqFiles.stream()
        .map(tsFileResourceCandidate -> tsFileResourceCandidate.resource)
        .collect(Collectors.toList());
  }
Filter the unseq files into the compaction. Unseq files should be not deleted or over ttl. To
ensure that the compaction is correct, return as soon as it encounters the file being compacted
or compaction candidate. Therefore, a cross space compaction can only be performed serially
under a time partition in a VSG.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/compaction/selector/utils/CrossSpaceCompactionCandidate.java