| From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Stephen Frost <sfrost(at)snowman(dot)net>, Christoph Berg <myon(at)debian(dot)org>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: compute_query_id and pg_stat_statements |
| Date: | 2021-05-14 02:21:59 |
| Message-ID: | 20210514022159.l2v7w2h4al3zjhzn@nol |
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| Lists: | pgsql-hackers |
On Thu, May 13, 2021 at 09:47:02PM -0400, Tom Lane wrote:
> Julien Rouhaud <rjuju123(at)gmail(dot)com> writes:
> > On Fri, May 14, 2021 at 3:12 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >> I was surprised it was ~2%.
>
> > Just to be clear, the 2% was a worst case scenario, ie. a very fast
> > read-only query on small data returning a single row. As soon as you
> > get something more realistic / expensive the overhead goes away.
>
> Of course, for plenty of people that IS the realistic scenario that
> they care about max performance for.
I'm not arguing that the scenario is unrealistic. I'm arguing that retrieving
the first row of a join between pg_class and pg_attribute on an otherwise
vanilla database may not be the most representative workload, especially when
you take into account that it was done on hardware that still took 3 ms to do
that.
Unfortunately my laptop is pretty old and has already proven multiple time to
give unreliable benchmark results, so I'm not confident at all that those 2%
are even real outside of my machine.
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