private IWritableMemChunkGroup createMemChunkGroupIfNotExistAndGet(
      IDeviceID deviceId, List<IMeasurementSchema> schemaList) {
    IWritableMemChunkGroup memChunkGroup =
        memTableMap.computeIfAbsent(deviceId, k -> new WritableMemChunkGroup());
    for (IMeasurementSchema schema : schemaList) {
      if (schema != null && !memChunkGroup.contains(schema.getMeasurementName())) {
        seriesNumber++;
      }
    }
    return memChunkGroup;
  }
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