@Override
  public long delete(ModEntry modEntry) {
    int deletedPointsNumber = 0;
    Set<String> measurements = memChunk.getAllMeasurements();
    List<String> columnsToBeRemoved = new ArrayList<>();
    for (String measurement : measurements) {
      if (!modEntry.affects(measurement)) {
        continue;
      }

      Pair<Integer, Boolean> deletedNumAndIsFullyDeleted =
          memChunk.deleteDataFromAColumn(
              modEntry.getStartTime(), modEntry.getEndTime(), measurement);
      deletedPointsNumber += deletedNumAndIsFullyDeleted.left;
      if (Boolean.TRUE.equals(deletedNumAndIsFullyDeleted.right)) {
        columnsToBeRemoved.add(measurement);
      }
    }

    for (String columnToBeRemoved : columnsToBeRemoved) {
      memChunk.removeColumn(columnToBeRemoved);
    }
    return deletedPointsNumber;
  }
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