From: Stephen Frost <sfrost@snowman.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: depesz@depesz.com, pgsql-general <pgsql-general@lists.postgresql.org>
Subject: Re: Can we get rid of repeated queries from pg_dump?
Date: Fri, 27 Aug 2021 18:27:20 -0400
Message-ID: <20210827222720.GV17906@tamriel.snowman.net> (raw)
In-Reply-To: <900377.1630103105@sss.pgh.pa.us>
References: <20210826084430.GA26282@depesz.com>
<648517.1629986527@sss.pgh.pa.us>
<20210826140827.GA15868@depesz.com>
<649446.1629987629@sss.pgh.pa.us>
<20210826160644.GA3120@depesz.com>
<e6a7503afd115d111fbb96c5787906d73cfe2605.camel@cybertec.at>
<896732.1630099403@sss.pgh.pa.us>
<20210827215836.GT17906@tamriel.snowman.net>
<900377.1630103105@sss.pgh.pa.us>
Greetings,
* Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Stephen Frost <sfrost@snowman.net> writes:
> > * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> >> I experimented with the attached, very quick-n-dirty patch to collect
> >> format_type results during the initial scan of pg_type, instead. On the
> >> regression database in HEAD, it reduces the number of queries pg_dump
> >> issues from 3260 to 2905; but I'm having a hard time detecting any net
> >> performance change.
>
> > Seems like the issue here is mainly just the latency of each query being
> > rather high compared to most use-cases, so local testing where there's
> > basically zero latency wouldn't see any change in timing, but throw a
> > trans-atlantic or worse amount of latency between the system running
> > pg_dump and the PG server and you'd see notable wall-clock savings in
> > time.
>
> Yeah. What I was more concerned about was the potential downside
> of running format_type() for each pg_type row, even though we might
> use only a few of those results. The fact that I'm *not* seeing
> a performance hit with a local server is encouraging from that
> standpoint.
Ah, yes, agreed.
Thanks!
Stephen
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To: pgsql-general@postgresql.org
Cc: sfrost@snowman.net, tgl@sss.pgh.pa.us, laurenz.albe@cybertec.at, pgsql-general@lists.postgresql.org
Subject: Re: Can we get rid of repeated queries from pg_dump?
In-Reply-To: <20210827222720.GV17906@tamriel.snowman.net>
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