Date: Wed, 20 Dec 2023 21:16:14 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: "Kumar, Sachin" <ssetiya@amazon.com>, Jan Wieck <jan@wi3ck.info>,
	Bruce Momjian <bruce@momjian.us>, Zhihong Yu <zyu@yugabyte.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	Magnus Hagander <magnus@hagander.net>,
	Robins Tharakan <tharakan@gmail.com>,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: pg_upgrade failing for 200+ million Large Objects
Message-ID: <20231221031614.GA836232@nathanxps13>
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On Wed, Dec 20, 2023 at 06:47:44PM -0500, Tom Lane wrote:
> I have spent some more effort in this area and developed a patch
> series that I think addresses all of the performance issues that
> we've discussed in this thread, both for pg_upgrade and more
> general use of pg_dump/pg_restore.  Concretely, it absorbs
> the pg_restore --transaction-size switch that I proposed before
> to cut the number of transactions needed during restore, and
> rearranges the representation of BLOB-related TOC entries to
> reduce the client-side memory requirements, and fixes some
> ancient mistakes that prevent both selective restore of BLOBs
> and parallel restore of BLOBs.
> 
> As a demonstration, I made a database containing 100K empty blobs,
> and measured the time needed to dump/restore that using -Fd
> and -j 10.  HEAD doesn't get any useful parallelism on blobs,
> but with this patch series we do:
> 
> 		dump	restore
> HEAD:		14sec	15sec
> after 0002:	7sec	10sec
> after 0003:	7sec	3sec

Wow, thanks for putting together these patches.  I intend to help review,
but I'm not sure I'll find much time to do so before the new year.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com