From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stephen Frost <sfrost@snowman.net>
cc: Laurenz Albe <laurenz.albe@cybertec.at>, depesz@depesz.com,
        pgsql-general <pgsql-general@lists.postgresql.org>
Subject: Re: Can we get rid of repeated queries from pg_dump?
In-reply-to: <20210827215836.GT17906@tamriel.snowman.net>
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Comments: In-reply-to Stephen Frost <sfrost@snowman.net>
	message dated "Fri, 27 Aug 2021 17:58:36 -0400"
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Date: Fri, 27 Aug 2021 18:25:05 -0400
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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.

			regards, tom lane