public int compareTo(BucketId other) {
        if (id >>> 32 == other.id >>> 32) {
            if ((id & 0xFFFFFFFFL) > (other.id & 0xFFFFFFFFL)) {
                return 1;
            } else if ((id & 0xFFFFFFFFL) < (other.id & 0xFFFFFFFFL)) {
                return -1;
            }
            return 0;
        } else if ((id >>> 32) > (other.id >>> 32)) {
            return 1;
        } else {
            return -1;
        }
    }
Creates a bucket id with the given raw bucket id. This is a 64 bit mask
where the first 6 MSB bits set how many LSB bits should actually be used.
Right now it only have simple functionality. More will be added for it
to be configurable.
document/src/main/java/com/yahoo/document/BucketId.java