code: func (db *DB) hDelete(t *batch, key []byte) int64 {
  	sk := db.hEncodeSizeKey(key)
  	start := db.hEncodeStartKey(key)
  	stop := db.hEncodeStopKey(key)
  
  	var num int64
  	it := db.bucket.RangeLimitIterator(start, stop, store.RangeROpen, 0, -1)
  	for ; it.Valid(); it.Next() {
  		t.Delete(it.Key())
  		num++
  	}
  	it.Close()
  
  	t.Delete(sk)
  	return num
  }
docs: //	ps : here just focus on deleting the hash data,
  //		 any other likes expire is ignore.