From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Showing primitive index scan count in EXPLAIN ANALYZE (for skip scan and SAOP scans) |
Date: | 2024-08-28 13:25:31 |
Message-ID: | CA+TgmobTLnrxhomd2nxfHg3BeY5cMALBG-SKJZrHPSGPZ1LdSQ@mail.gmail.com |
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On Tue, Aug 27, 2024 at 3:04 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Geoghegan <pg(at)bowt(dot)ie> writes:
> > I see value in making it obvious to users when and how
> > pg_stat_all_indexes.idx_scan advances. Being able to easily relate it
> > to EXPLAIN ANALYZE output is useful, independent of whether or not
> > SAOPs happen to be used. That's probably the single best argument in
> > favor of showing "Index Searches: N" unconditionally. But I'm
> > certainly not going to refuse to budge over that.
>
> TBH, I'm afraid that this patch basically is exposing numbers that
> nobody but Peter Geoghegan and maybe two or three other hackers
> will understand, and even fewer people will find useful (since the
> how-many-primitive-scans behavior is not something users have any
> control over, IIUC). I doubt that "it lines up with
> pg_stat_all_indexes.idx_scan" is enough to justify the additional
> clutter in EXPLAIN. Maybe we should be going the other direction
> and trying to make pg_stat_all_indexes count in a less detailed but
> less surprising way, ie once per indexscan plan node invocation.
I kind of had that reaction too initially, but I think that was mostly
because "Primitive Index Scans" seemed extremely unclear. I think
"Index Searches" is pretty comprehensible, honestly. Why shouldn't
someone be able to figure out what that means?
Might make sense to restrict this to VERBOSE mode, too.
--
Robert Haas
EDB: http://www.enterprisedb.com
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