@Override
  public boolean contains(String measurement) {
    // used for calculate memtable size
    if (AlignedPath.VECTOR_PLACEHOLDER.equals(measurement)) {
      return true;
    }
    return memChunk.containsMeasurement(measurement);
  }
Check whether this MemChunkGroup contains a measurement. If a VECTOR_PLACEHOLDER passed from
outer, always return true because AlignedMemChunkGroup existing.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/memtable/AlignedWritableMemChunkGroup.java