| From: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Michail Nikolaev <michail(dot)nikolaev(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, reshkekirill <reshkekirill(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Slow standby snapshot |
| Date: | 2022-11-22 17:06:40 |
| Message-ID: | CANbhV-FL4wjeb2AjEdSUf5J3QToWpoSnm4rLQhffCzL6P9z4-Q@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, 22 Nov 2022 at 16:53, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> writes:
> > On Tue, 22 Nov 2022 at 16:28, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> If we do those things, do we need a wasted-work counter at all?
>
> > The wasted work counter works well to respond to heavy read-only
> > traffic and also avoids wasted compressions for write-heavy workloads.
> > So I still like it the best.
>
> This argument presumes that maintenance of the counter is free,
> which it surely is not. I don't know how bad contention on that
> atomically-updated variable could get, but it seems like it could
> be an issue when lots of processes are acquiring snapshots.
I understand. I was assuming that you and Andres liked that approach.
In the absence of that approach, falling back to a counter that
compresses every N xids would be best, in addition to the two new
forced compression events.
--
Simon Riggs http://www.EnterpriseDB.com/
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Andres Freund | 2022-11-22 17:10:00 | Re: [PoC] Improve dead tuple storage for lazy vacuum |
| Previous Message | Maxim Orlov | 2022-11-22 17:02:52 | Re: [BUG] FailedAssertion in SnapBuildPurgeOlderTxn |