public long getTTLForCurrentDevice() {
    return ttlForCurrentDevice;
  }
Return next device that is minimal in lexicographical order.

@return Pair of device full path and whether this device is aligned
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/compaction/execute/utils/MultiTsFileDeviceIterator.java