private IChunkMetadata buildChunkMetaDataForMemoryChunk(
      String measurement, long startTime, long endTime, List<TimeRange> deletionList) {
    TimeStatistics timeStatistics = new TimeStatistics();
    timeStatistics.setStartTime(startTime);
    timeStatistics.setEndTime(endTime);

    // ChunkMetaData for memory is only used to get time statistics, the dataType is irrelevant.
    IChunkMetadata chunkMetadata =
        new ChunkMetadata(
            measurement,
            TSDataType.UNKNOWN,
            TSEncoding.PLAIN,
            CompressionType.UNCOMPRESSED,
            0,
            timeStatistics);
    for (TimeRange timeRange : deletionList) {
      chunkMetadata.insertIntoSortedDeletions(timeRange);
    }
    return chunkMetadata;
  }
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