@Override
    public int rootBlockContainingKey(final byte[] key, int offset, int length,
      CellComparator comp) {
      // This should always be called with Cell not with a byte[] key
      throw new UnsupportedOperationException("Cannot find for a key containing plain byte "
        + "array. Only cell based keys can be searched for");
    }
Adds a new entry in the root block index. Only used when reading.
@param key      Last key in the block
@param offset   file offset where the block is stored
@param dataSize the uncompressed data size
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java