y/y.go
func ParseTs(key []byte) uint64 {
	if len(key) <= 8 {
		return 0
	}
	return math.MaxUint64 - binary.BigEndian.Uint64(key[len(key)-8:])
}
func ParseTs(key []byte) uint64 {
	if len(key) <= 8 {
		return 0
	}
	return math.MaxUint64 - binary.BigEndian.Uint64(key[len(key)-8:])
}
// ParseTs parses the timestamp from the key bytes.