public synchronized List<TTimePartitionSlot> filterUnassignedDataPartitionSlots(
      List<TTimePartitionSlot> partitionSlots) {
    List<TTimePartitionSlot> result = new Vector<>();
    partitionSlots.forEach(
        timePartitionSlot -> {
          if (!seriesPartitionMap.containsKey(timePartitionSlot)) {
            result.add(timePartitionSlot);
          }
        });
    return result;
  }
Only Leader use this interface. And this interface is synchronized. Thread-safely filter no
assigned DataPartitionSlots within the specific SeriesPartitionSlot.

@param partitionSlots TimePartitionSlots
@return Unassigned PartitionSlots
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/partition/SeriesPartitionTable.java