From: Tom Lane <tgl@sss.pgh.pa.us>
To: depesz@depesz.com
cc: Laurenz Albe <laurenz.albe@cybertec.at>,
        pgsql-general <pgsql-general@lists.postgresql.org>
Subject: Re: Can we get rid of repeated queries from pg_dump?
In-reply-to: <20210830074442.GB15241@depesz.com>
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 <648517.1629986527@sss.pgh.pa.us> <20210826140827.GA15868@depesz.com>
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Comments: In-reply-to hubert depesz lubaczewski <depesz@depesz.com>
	message dated "Mon, 30 Aug 2021 09:44:43 +0200"
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Date: Mon, 30 Aug 2021 10:11:22 -0400
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hubert depesz lubaczewski <depesz@depesz.com> writes:
> On Fri, Aug 27, 2021 at 05:23:23PM -0400, Tom Lane wrote:
>> I experimented with the attached, very quick-n-dirty patch to collect
>> format_type results during the initial scan of pg_type, instead.

> So, I applied it to brand new HEAD from git, Result:
> From total of 9173 queries it went down to 4178.
> Originally 5000 type queries, now 19!
> This is actually strange given that previously it was asking querying
> about 83 separate type oids. But, as far as I was able to check with
> "pg_restore -l" (from -Fc dump), results are the same.

Hm.  So we're still no wiser than before about how such a small (in
terms of number of objects) database could have produced so many
getFormattedTypeName calls.  Plus, this result raises a new question:
with the patch, I think you shouldn't have seen *any* queries of that
form.  Where are the 19 survivors coming from?

I don't suppose you could send me a schema-only dump of that
database, off-list?  I'm now quite curious.

> But since we're looking at it, and with both patches applied, I looked
> at the next most common query. Which is:
> [ collection of details about a function ]

> The thing is - even though it was called 1804 times, dump contains data =
only
> about 107 functions (pg_restore -l schema.dump | grep -c FUNCTION), so i=
t kinda
> seems that 94% of these calls is not needed.

Hm.  It's not doing that for *every* row in pg_proc, at least.
I speculate that it is collecting and then not printing the info
about functions that are in extensions --- can you check on
how many there are of those?

(Actually, if you've got a whole lot of objects inside extensions,
maybe that explains the 5000 calls?)

			regards, tom lane