code: func (db *DB) HClear(key []byte) (int64, error) {
  	if err := checkKeySize(key); err != nil {
  		return 0, err
  	}
  
  	t := db.hashBatch
  	t.Lock()
  	defer t.Unlock()
  
  	num := db.hDelete(t, key)
  	db.rmExpire(t, HashType, key)
  
  	err := t.Commit()
  	return num, err
  }
docs: // HClear clears the data.