Re: 9.6.11- could not truncate directory "pg_serial": apparent wraparound

Hi,

Got this issue again.
Settings on the platform (PG 9.6.11):
max_pred_locks_per_transaction = 3000
max_connections = 800

Despite the fact that documentation says:
> with the exception of fast-path locks, each lock manager will deliver a
consistent set of results
I've noticed the following:
1. pg_locks showed 2 million SIReadLocks for the pid that has been in the
"idle" state for a dozen of seconds already.
2. pg_locks showed count of 5 million SIReadLock granted although I
expected a limit of 2.4 million SIReadLocks with settings provided above.

And still no any signs of serializable transactions that could live for a 1
billion xids.
--
Pavel Suderevsky
E: psuderevsky(at)gmail(dot)com

вт, 9 апр. 2019 г. в 16:00, Pavel Suderevsky <psuderevsky(at)gmail(dot)com>:

> On Sun, Apr 7, 2019 at 2:31 AM Pavel Suderevsky <psuderevsky(at)gmail(dot)com>
>> wrote:
>> > Probably if you advise me what could cause "pg_serial": apparent
>> wraparound messages I would have more chances to handle all the performance
>> issues.
>>
>> Did you see that warning at some point before the later error?
>>
> Thomas,
>
> Thank you for your reply!
>
> No, there have never been such warnings.
>
> I wonder if this condition required you to have a serializable
>> transaction running (or prepared) while you consume 2^30 AKA ~1
>> billion xids. I think it is unreachable in v11+ because commit
>> e5eb4fa8 allowed for more SLRU pages to avoid this artificially early
>> wrap.
>
>
> Do I understand right that this is about Virtual txids? Have no idea how
> even a something close to a billion of transaction ids could be consumed on
> this system.
>
> --
> Pavel Suderevsky
> E: psuderevsky(at)gmail(dot)com
>