| From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(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 01:36:19 |
| Message-ID: | CAOBaU_aim8mKxDsX+etUzFF7M8SSP3UDL9J98a6x2USXFNgHrw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, May 14, 2021 at 3:12 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> > Maybe we should revert this thing pending somebody doing the work to
> > make a version of queryid labeling that actually is negligibly cheap.
> > It certainly seems like that could be done; one more traversal of the
> > parse tree can't be that expensive in itself. I suspect that the
> > performance problem is with the particular hashing mechanism that
> > was used, which looks mighty ad-hoc anyway.
>
> 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. For
reference here is the detail:
https://www.postgresql.org/message-id/CAOBaU_ZVmGPfKTwZ6cM_qdzaF2E1gMkrLDMwwLy4Z1JxQ6=CZg@mail.gmail.com
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