Date: Mon, 17 Mar 2025 20:01:48 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: Jeff Davis <pgsql@j-davis.com>, Robert Treat <rob@xzilla.net>,
	Robert Haas <robertmhaas@gmail.com>,
	Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>,
	Michael Paquier <michael@paquier.xyz>,
	jian he <jian.universality@gmail.com>,
	Bruce Momjian <bruce@momjian.us>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
	Magnus Hagander <magnus@hagander.net>,
	Stephen Frost <sfrost@snowman.net>,
	Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
	Peter Smith <smithpb2250@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	alvherre@alvh.no-ip.org
Subject: Re: Statistics Import and Export
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On Mon, Mar 17, 2025 at 07:24:46PM -0400, Corey Huinker wrote:
> On Mon, Mar 17, 2025 at 10:24 AM Nathan Bossart <nathandbossart@gmail.com>
> wrote:
>> I'm assuming that writing a completely different TOC on the second pass
>> would corrupt the dump file.  Perhaps we could teach it to skip stats
>> entries on the second pass or something, but I'm not too wild about adding
>> to the list of invasive changes we're making last-minute for v18.
> 
> I'm confused, are they needed in both places?

AFAICT yes.  The second pass rewrites the TOC to udpate the data offset
information.  If we wrote a different TOC the second time around, then the
dump file would be broken, right?

		/*
		 * If possible, re-write the TOC in order to update the data offset
		 * information.  This is not essential, as pg_restore can cope in most
		 * cases without it; but it can make pg_restore significantly faster
		 * in some situations (especially parallel restore).
		 */
		if (ctx->hasSeek &&
			fseeko(AH->FH, tpos, SEEK_SET) == 0)
			WriteToc(AH);

-- 
nathan