public static void combineModsInInnerCompaction(
      Collection<TsFileResource> sourceFiles, TsFileResource targetTsFile) throws IOException {
    if (TsFileResource.useSharedModFile) {
      return;
    }
    Set<ModEntry> modifications = new HashSet<>();
    for (TsFileResource mergeTsFile : sourceFiles) {
      try (ModificationFile sourceCompactionModificationFile = mergeTsFile.getCompactionModFile()) {
        modifications.addAll(sourceCompactionModificationFile.getAllMods());
      }
    }
    updateOneTargetMods(targetTsFile, modifications);
  }
Collect all the compaction modification files of source files, and combines them as the
modification file of target file.

@throws IOException if io errors occurred
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/compaction/execute/utils/CompactionUtils.java