protected void markNullValue(int arrayIndex, int elementIndex) {
    // init bitMap if doesn't have
    if (bitMap == null) {
      List<BitMap> localBitMap = new ArrayList<>(getDefaultArrayNum());
      for (int i = 0; i < timestamps.size(); i++) {
        localBitMap.add(new BitMap(ARRAY_SIZE));
      }
      bitMap = localBitMap;
    }
    // if the bitmap in arrayIndex is null, init the bitmap
    if (bitMap.get(arrayIndex) == null) {
      bitMap.set(arrayIndex, new BitMap(ARRAY_SIZE));
    }

    // mark the null value in the current bitmap
    bitMap.get(arrayIndex).mark(elementIndex);
  }
Get the row index value in index column.

@param index row index
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/utils/datastructure/TVList.java