Method HDecrBy

structure/hash.go:815–882

HDecrBy decrements the integer value of a hash field by the given number. It takes a string key 'k', a field 'f', and a decrement value 'decrement'. It returns the updated value after decrement and any possible error. Parameters: k: The key of the hash table. f: The field whose value needs to be

(key string, field interface{}, decrement int64)

//	int64: The updated value of the field after decrement.
//	error: An error if occurred during the operation, or nil on success.
func (hs *HashStructure) HDecrBy(key string, field interface{}, decrement int64) (int64, error) {
	// Convert the parameters to bytes
	k := stringToBytesWithKey(key)

	// Convert the parameters to bytes
	f, err, _ := interfaceToBytes(field)
	if err != nil {
		return 0, err
	}

	// Check the parameters
	if len(k) == 0 || len(f) == 0 {
		return 0, _const.ErrKeyIsEmpty
	}

	// Find the hash metadata by the given key
	hashMeta, err := hs.findHashMeta(key, Hash)
	if err != nil {
		return 0, err
	}

	// If the counter is 0, return 0
	if hashMeta.counter == 0 {
		return 0, nil
	}

	// Create a new HashField
	hf := &HashField{
		field:   f,
		key:     k,
		version: hashMeta.version,
	}

	// Encode the HashField
	hfBuf := hf.encodeHashField()

	// Get the field from the database
	value, err := hs.db.Get(hfBuf)
	if err != nil && err == _const.ErrKeyNotFound {
		return 0, nil
	}

	// Convert the value to int64
	val, err := strconv.ParseInt(string(value), 10, 64)
	if err != nil {
		return 0, err
	}

	// Subtract the decrement from the value
	val -= decrement

	// Convert the value to string
	value = []byte(strconv.FormatInt(val, 10))

	// Create a new write batch
	batch := hs.db.NewWriteBatch(config.DefaultWriteBatchOptions)

	// Put the field to the database