Re: INSERT ... ON CONFLICT {UPDATE | IGNORE} 2.0

On Wed, Feb 4, 2015 at 10:03 AM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Wed, Feb 4, 2015 at 9:54 AM, Heikki Linnakangas
> <hlinnakangas(at)vmware(dot)com> wrote:
>> I had compiled with -O0, but without assertions. I tried now again with -O3.
>> It's been running for about 10 minutes now, and I haven't seen any errors.
>
> Did you run with an artificially high XID burn rate (i.e. did you also
> apply Jeff's modifications to Postgres, and specify a high burn rate
> using his custom GUC)? Maybe that was important.

Excuse me: I now see that you specifically indicated that you did. But
looks like your XID burn rate was quite a lot higher than mine
(assuming that you were consistent in using " jj_xid=10000", although
I'm not asserting that that was significant).

I attach a log of output from an example session where exclusion
constraints are shown to break (plus the corresponding server log,
plus /proc/cpuinfo on the off chance that that's significant). As you
can from the fact that the span of time recorded in the log is only a
couple of minutes, this is really easy for me to
recreate....sometimes. I could not recreate the problem with only 4
clients (on this 8 core server) after a few dozen attempts, and then I
couldn't recreate the issue at all, so clearly those details matter.
It might have something to do with CPU scaling, which I've found can
significantly affect outcomes for things like this (looks like my
hosting provider changed settings in the system BIOS recently, such
that I cannot set the CPU governor to "performance").

Perhaps you could take a crack at recreating this, Jeff?

Thanks
--
Peter Geoghegan