public CrossCompactionTaskResourceSplit nextSplit() {
    return nextSplit;
  }
CrossSpaceCompactionResource manages files and caches of readers to avoid unnecessary object
creations and file openings.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/compaction/selector/utils/CrossSpaceCompactionCandidate.java