public static void deleteEmptyDir(File dir) {
    if (!dir.isDirectory()) {
      return;
    }
    for (File f : dir.listFiles()) {
      deleteEmptyDir(f);
    }
    dir.delete();
  }
Clear all generated and merged files in the test directory
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/compaction/utils/CompactionClearUtils.java