public void releaseFileScanHandle() {
    if (curIndex >= unSeqSize) {
      seqFileScanHandles.set(curIndex - unSeqSize, null);
    } else {
      unseqFileScanHandles.set(curIndex, null);
    }
  }
Iterate the list in descending order of time, as more recent entries are less likely to have
their TsFile resources downgraded
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/read/QueryDataSourceForRegionScan.java