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From: Peter Geoghegan <pg@bowt.ie>
Date: Tue, 7 Mar 2023 21:21:00 -0800
Message-ID: <CAH2-WzmbW4Zvh5gWXF9i5UwMk2DnnmueKR+ib-W7e6rc9-Z2Zw@mail.gmail.com>
Subject: Re: Testing autovacuum wraparound (including failsafe)
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Ian Lawrence Barwick <barwick@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, 
	Andres Freund <andres@anarazel.de>, Anastasia Lubennikova <lubennikovaav@gmail.com>, 
	pgsql-hackers <pgsql-hackers@postgresql.org>
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On Fri, Mar 3, 2023 at 3:34=E2=80=AFAM Heikki Linnakangas <hlinnaka@iki.fi>=
 wrote:
> I took a different approach to consuming the XIDs. Instead of setting
> nextXID directly, bypassing GetNewTransactionId(), this patch introduces
> a helper function to call GetNewTransactionId() repeatedly. But because
> that's slow, it does include a shortcut to skip over "uninteresting"
> XIDs. Whenever nextXid is close to an SLRU page boundary or XID
> wraparound, it calls GetNewTransactionId(), and otherwise it bumps up
> nextXid close to the next "interesting" value. That's still a lot slower
> than just setting nextXid, but exercises the code more realistically.

Surely your tap test should be using single user mode?  Perhaps you
missed the obnoxious HINT, that's part of the WARNING that the test
parses?  ;-)

This is a very useful patch. I certainly don't want to make life
harder by (say) connecting it to the single user mode problem.
But...the single user mode thing really needs to go away. It's just
terrible advice, and actively harms users.

--=20
Peter Geoghegan