Пример #1
0
// Increment fetches the varint encoded int64 value specified by key
// and adds "inc" to it then re-encodes as varint. The newly incremented
// value is returned.
func (mvcc *MVCC) Increment(key Key, timestamp proto.Timestamp, txnID []byte, inc int64) (int64, error) {
	// Handle check for non-existence of key. In order to detect
	// the potential write intent by another concurrent transaction
	// with a newer timestamp, we need to use the max timestamp
	// while reading.
	val, err := mvcc.Get(key, proto.MaxTimestamp, txnID)
	if err != nil {
		return 0, err
	}

	var int64Val int64
	// If the value exists, attempt to decode it as a varint.
	if len(val.Bytes) != 0 {
		decoded, err := encoding.Decode(key, val.Bytes)
		if err != nil {
			return 0, err
		}
		if _, ok := decoded.(int64); !ok {
			return 0, util.Errorf("received value of wrong type %v", reflect.TypeOf(decoded))
		}
		int64Val = decoded.(int64)
	}

	// Check for overflow and underflow.
	if encoding.WillOverflow(int64Val, inc) {
		return 0, util.Errorf("key %q with value %d incremented by %d results in overflow", key, int64Val, inc)
	}

	if inc == 0 {
		return int64Val, nil
	}

	r := int64Val + inc
	encoded, err := encoding.Encode(key, r)
	if err != nil {
		return 0, util.Errorf("error encoding %d", r)
	}

	err = mvcc.Put(key, timestamp, proto.Value{Bytes: encoded, Timestamp: timestamp}, txnID)
	if err != nil {
		return 0, err
	}
	return r, nil
}
Пример #2
0
// Increment fetches the varint encoded int64 value specified by key
// and adds "inc" to it then re-encodes as varint. The newly incremented
// value is returned.
func Increment(engine Engine, key Key, inc int64) (int64, error) {
	// First retrieve existing value.
	val, err := engine.Get(key)
	if err != nil {
		return 0, err
	}
	var int64Val int64
	// If the value exists, attempt to decode it as a varint.
	if len(val) != 0 {
		decoded, err := encoding.Decode(key, val)
		if err != nil {
			return 0, err
		}
		if _, ok := decoded.(int64); !ok {
			return 0, util.Errorf("received value of wrong type %v", reflect.TypeOf(decoded))
		}
		int64Val = decoded.(int64)
	}

	// Check for overflow and underflow.
	if encoding.WillOverflow(int64Val, inc) {
		return 0, util.Errorf("key %q with value %d incremented by %d results in overflow", key, int64Val, inc)
	}

	if inc == 0 {
		return int64Val, nil
	}

	r := int64Val + inc
	encoded, err := encoding.Encode(key, r)
	if err != nil {
		return 0, util.Errorf("error encoding %d", r)
	}
	if err = engine.Put(key, encoded); err != nil {
		return 0, err
	}
	return r, nil
}