A shorter non-repeating alphanumeric code than UUID in MySQL

Question

Is it possible for MySQL database to generate a 5 or 6 digit code comprised of only numbers and letters when I insert a record? If so how?

Just like goo.gl, bit.ly and j

Answer 1

Try this:

SELECT LEFT(UUID(), 6);

Answer 2

I recommend using Redis for this task, actually. It has all the features that make this task suitable for its use. Foremost, it is very good at searching a big list for a value.

We will create two lists, buffered_ids, and used_ids. A cronjob will run every 5 minutes (or whatever interval you like), which will check the length of buffered_ids and keep it above, say, 5000 in length. When you need to use an id, pop it from buffered_ids and add it to used_ids.

Redis has sets, which are unique items in a collection. Think of it as a hash where the keys are unique and all the values are "true".

Your cronjob, in bash:

log(){ local x=$1 n=2 l=-1;if [ "$2" != "" ];then n=$x;x=$2;fi;while((x));do let l+=1 x/=n;done;echo $l; }
scale=`redis-cli SCARD used_ids`
scale=`log 16 $scale`
scale=$[ scale + 6]
while [ `redis-cli SCARD buffered_ids` -lt 5000 ]; do
    uuid=`cat /dev/urandom | tr -cd "[:alnum:]" | head -c ${1:-$scale}`
    if [ `redis-cli SISMEMBER used_ids $uuid` == 1]; then
        continue
    fi
    redis-cli SADD buffered_ids $uuid
done

To grab the next uid for use in your application (in pseudocode because you did not specify a language)

$uid = redis('SPOP buffered_ids');
redis('SADD used_ids ' . $uid);

edit actually there's a race condition there. To safely pop a value, add it to used_ids first, then remove it from buffered_ids.

$uid = redis('SRANDMEMBER buffered_ids');
redis('SADD used_ids ' . $uid);
redis('SREM buffered_ids ' . $uid);