@Override
  public DataBlockEncoding getEffectiveEncodingInCache(boolean isCompaction) {
    return dataBlockEncoder.getEffectiveEncodingInCache(isCompaction);
  }
@return Midkey for this file. We work with block boundaries only so returned midkey is an
        approximation only.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java