private long[] calculateStartEndTime(long[] timestamps, List<BitMap> bitMaps, int column) {
    if (bitMaps.isEmpty()) {
      return new long[] {timestamps[0], timestamps[timestamps.length - 1]};
    }
    long startTime = -1, endTime = -1;
    for (int i = 0; i < timestamps.length; i++) {
      if (!bitMaps.get(i).isMarked(column)) {
        startTime = timestamps[i];
        break;
      }
    }

    for (int i = timestamps.length - 1; i >= 0; i--) {
      if (!bitMaps.get(i).isMarked(column)) {
        endTime = timestamps[i];
        break;
      }
    }
    return new long[] {startTime, endTime};
  }
Create this MemChunk if it's not exist.

@param deviceId device id
@param schemaList measurement schemaList
@return this MemChunkGroup
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/memtable/AbstractMemTable.java