Hi!
On May 13, Tatjana A Nuernberg wrote:
> ChangeSet@stripped, 2008-05-13 05:38:24+02:00, tnurnberg@stripped +3 -0
> Bug#35848: UUID() returns UUIDs with the wrong time
> sql/item_strfunc.cc@stripped, 2008-05-13 05:38:24+02:00,
> tnurnberg@stripped +10 -4
> correct offset for date/time-part of UUID.
> also make sure that when we counted into the future earlier
> (several UUIDs generated in same tick), we only give back
> as many "borrowed" ticks as we can without duplicating past
> timestamps.
>
> diff -Nrup a/sql/item_strfunc.cc b/sql/item_strfunc.cc
> --- a/sql/item_strfunc.cc 2007-01-11 14:44:59 +01:00
> +++ b/sql/item_strfunc.cc 2008-05-13 05:38:24 +02:00
> @@ -3026,10 +3027,15 @@ String *Item_func_uuid::val_str(String *
> {
> if (nanoseq)
> {
> - tv-=nanoseq;
> - nanoseq=0;
> + DBUG_ASSERT((tv > uuid_time) && (nanoseq > 0));
> + /*
> + -1 so we won't make tv= uuid_time for nanoseq >= (tv - uuid_time)
> + */
> + long delta= min(nanoseq, tv - uuid_time -1);
> + DBUG_PRINT("uuid",("unwinding time by %ld of %ld (%ld -> %ld)",(long)
> delta, (long) nanoseq, (long) uuid_time, (long) tv));
> + tv-= delta;
> + nanoseq-= delta;
> }
> - DBUG_ASSERT(tv > uuid_time);
> }
> uuid_time=tv;
> pthread_mutex_unlock(&LOCK_uuid_generator);
This is bug#35514 that you're fixing, so you should assign it to
yourself.
As you could see from that bugreport, my idea of a fix was to add a
sleep in case of tv <= uuid_time to limit the rate of UUID generation.
Your solution is ok, but it creates a problem later when nanoseq
overflows. It looks like it's quite possible to overflow it in a
reasonable amount of time. You need a protection for that - and the only
solution I see is set_clock_seq_str().
Regards / Mit vielen Grüssen,
Sergei
--
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <serg@stripped>
/ /|_/ / // /\ \/ /_/ / /__ Principal Software Engineer/Server Architect
/_/ /_/\_, /___/\___\_\___/ Sun Microsystems GmbH, HRB München 161028
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