| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Jeff Davis <pgsql(at)j-davis(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, John Naylor <john(dot)naylor(at)enterprisedb(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: New strategies for freezing, advancing relfrozenxid early |
| Date: | 2023-01-26 16:24:21 |
| Message-ID: | CAH2-Wz=pqEEOvNiUu+yqcKsPHarOcE1cL6w2OznGNs+MsdTd+w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jan 25, 2023 at 7:56 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > https://wiki.postgresql.org/wiki/Freezing/skipping_strategies_patch:_motivating_examples#Patch_2
> >
> > The difference between this and VACUUM FREEZE is described here:
> >
> > "Note how we freeze most pages, but still leave a significant number
> > unfrozen each time, despite using an eager approach to freezing
> > (2981204 scanned - 2355230 frozen = 625974 pages scanned but left
> > unfrozen). Again, this is because we don't freeze pages unless they're
> > already eligible to be set all-visible.
>
> The only reason there is a substantial difference is because of pgbench's
> uniform access pattern. Most real-world applications don't have that.
It's not pgbench! It's TPC-C. It's actually an adversarial case for
the patch series.
--
Peter Geoghegan
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