code: func (b *Batch) Replay(r BatchReplay) error {
  	for _, index := range b.index {
  		switch index.keyType {
  		case keyTypeVal:
  			r.Put(index.k(b.data), index.v(b.data))
  		case keyTypeDel:
  			r.Delete(index.k(b.data))
  		}
  	}
  	return nil
  }
docs: // Replay replays batch contents.