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In-Reply-To: <2c7d4202-31d4-4254-8ed0-484083b14624@iki.fi>
From: Maxim Orlov <orlovmg@gmail.com>
Date: Thu, 11 Dec 2025 15:47:53 +0300
Message-ID: 
 <CACG=ezaVcG-uoD+U1D-6ELe3H5zqQM0CsC5ts6yA_u=553+EXg@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
 Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Alexander Korotkov <aekorotkov@gmail.com>,
 wenhui qiu <qiuwenhuifx@gmail.com>,
	Postgres hackers <pgsql-hackers@lists.postgresql.org>
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On Thu, 11 Dec 2025 at 10:58, Heikki Linnakangas <hlinnaka@iki.fi> wrote:

>
> That's a great question and I've been wondering about it myself. It goes
> all the way to the initial commit where multixacts were introduced, and
> I don't see any particular reason for it even back then. Even in the
> very first version of multixact.c, IMO it would've been simpler to have
> the writer handle the wraparound.
>
> +1 This code is quite old. I don't see any particular reason for doing
it that way. Unfortunately, we were unable to prove the absence of
something, namely errors, in this instance. But there were no obvious
statements on why it should be in this manner. So, for me, it's much
clearer to increment and handle wraparound in one place rather
than spread it across multiple calls in the module.

-- 
Best regards,
Maxim Orlov.

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<div dir=3D"ltr"><div dir=3D"ltr"></div><br><div class=3D"gmail_quote gmail=
_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, 11 Dec 2025=
 at 10:58, Heikki Linnakangas &lt;<a href=3D"mailto:hlinnaka@iki.fi">hlinna=
ka@iki.fi</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding=
-left:1ex"><br>
That&#39;s a great question and I&#39;ve been wondering about it myself. It=
 goes <br>
all the way to the initial commit where multixacts were introduced, and <br=
>
I don&#39;t see any particular reason for it even back then. Even in the <b=
r>
very first version of multixact.c, IMO it would&#39;ve been simpler to have=
 <br>
the writer handle the wraparound.<br><br>
</blockquote></div><div>+1 This code is quite old. I don&#39;t see any part=
icular reason for doing<br>it that way. Unfortunately, we were unable to pr=
ove the absence of<br>something, namely errors, in this instance. But there=
 were no obvious<br>statements on why it should be in this manner. So, for =
me, it&#39;s much</div><div>clearer to increment and handle wraparound in o=
ne place rather</div><div>than spread it across multiple calls in the modul=
e.</div><br><span class=3D"gmail_signature_prefix">-- </span><br><div dir=
=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><div>Best regards,<br><=
/div><div>Maxim Orlov.</div></div></div></div>

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