code: func (i *smallIndex) load() {
  	it := i.db.NewIterator(util.BytesPrefix(i.prefix), nil)
  	defer it.Release()
  	for it.Next() {
  		val := string(it.Value())
  		id := binary.BigEndian.Uint32(it.Key()[len(i.prefix):])
  		if val != "" {
  			// Empty value means the entry has been deleted.
  			i.id2val[id] = val
  			i.val2id[val] = id
  		}
  		if id >= i.nextID {
  			i.nextID = id + 1
  		}
  	}
  }
docs: // load iterates over the prefix space in the database and populates the in
  // memory maps.