MIME-Version: 1.0
References: <CACG=ezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com>
 <CACG=ezaMncd0-BcGHBgsSR2eqHfrz9WznHGLKX8biz6zu-azGw@mail.gmail.com>
 <5ecc35f5-1111-47fc-8a02-36d89490a50d@iki.fi> <CACG=ezb9XTvd3ZmS0y8gUunx_wBBdJO7ou+BfCOnnA5jE-11vg@mail.gmail.com>
 <CACG=ezYFNqGjsxF6Vb2CHF6JzKcjhAFauaFm9js0nu_3Ngcdkw@mail.gmail.com>
 <CAGjGUA+dcV7veaCV1H65vCNsbS++nT8=ho772gDvsXUW9H7eXQ@mail.gmail.com>
 <CACG=ezYThNkf8QsDA-aQfEFEkqn2L=_uUL83z0vJstPRasbZqg@mail.gmail.com>
 <24b3deb6-a732-4256-847a-560f4bf39d59@iki.fi> <CACG=ezYtCatcRODS-ZkwhcxuqBKCuhEsZGBruw=dGCLoepF+ZA@mail.gmail.com>
 <ca451a6a-5b0f-433c-8ab9-b28b7f480bd7@iki.fi> <CACG=ezb680eb=JXh1ns=t5eGH3h9y-uTfT4tf3Xc8t2UH2q6tQ@mail.gmail.com>
 <CACG=ezZGQFBb0yepka8hU2BmJ48ujt3xa+aYLNL0BQPx0vqwZg@mail.gmail.com>
 <CACG=ezajc_Pcqmy6fcq-N8+LzCRMzOzJzez2_BgHEu-6RVJtKQ@mail.gmail.com>
 <4535f3aa-3220-4760-b1f5-2bc91f248e03@iki.fi> <CACG=ezbKwypBp=14q9+hMQApus3=1hKxJ9x1+KinUhtT48570Q@mail.gmail.com>
 <2bc58592-9d74-4af0-bdd1-1a88e8683f7c@iki.fi>
In-Reply-To: <2bc58592-9d74-4af0-bdd1-1a88e8683f7c@iki.fi>
From: Maxim Orlov <orlovmg@gmail.com>
Date: Tue, 7 Jan 2025 13:23:59 +0300
Message-ID: <CACG=ezZwdvsijzuXE3hex3xHcoz75EQYBXRTsQJVwbo5J5sS3g@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: wenhui qiu <qiuwenhuifx@gmail.com>, Alexander Korotkov <aekorotkov@gmail.com>, 
	Postgres hackers <pgsql-hackers@lists.postgresql.org>
Content-Type: multipart/alternative; boundary="00000000000053263f062b1b254d"
Archived-At: <https://www.postgresql.org/message-id/CACG%3DezZwdvsijzuXE3hex3xHcoz75EQYBXRTsQJVwbo5J5sS3g%40mail.gmail.com>
Precedence: bulk

--00000000000053263f062b1b254d
Content-Type: text/plain; charset="UTF-8"

On Thu, 2 Jan 2025 at 01:12, Heikki Linnakangas <hlinnaka@iki.fi> wrote:

>
> It might be best to just refuse the upgrade if oldestOffsetKnown==false.
> It's a very ancient corner case. It seems reasonable to require you to
> upgrade to a newer minor version and run VACUUM before upgrading. IIRC
> that sets oldestOffsetKnown.
>

I agree.  After all, we do already have a ready-made solution in the form
of a vacuum, do we?

If I understand all this multixact_old.c machinery correctly, in case of
oldestOffsetKnown==false
we should fail with "could not open file" or offset will be 0 in
GetOldMultiXactIdSingleMember.
So, I suppose we can put an analogue of SimpleLruDoesPhysicalPageExist call
in the beginning
of GetOldMultiXactIdSingleMember. And if either
SimpleLruDoesPhysicalPageExist return false
or a corresponding offset will be 0 we have to bail out with "oldest offset
does not exist, consider
running vacuum before pg_upgrdade" or smth. Please, correct me if I'm wrong.

-- 
Best regards,
Maxim Orlov.

--00000000000053263f062b1b254d
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, 2 Jan 2=
025 at 01:12, Heikki Linnakangas &lt;<a href=3D"mailto:hlinnaka@iki.fi">hli=
nnaka@iki.fi</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" styl=
e=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);paddin=
g-left:1ex"><br>
It might be best to just refuse the upgrade if oldestOffsetKnown=3D=3Dfalse=
. <br>
It&#39;s a very ancient corner case. It seems reasonable to require you to =
<br>
upgrade to a newer minor version and run VACUUM before upgrading. IIRC <br>
that sets oldestOffsetKnown.<br></blockquote><div>=C2=A0</div><div>I agree.=
=C2=A0 <span class=3D"gmail-HwtZe" lang=3D"en"><span class=3D"gmail-jCAhz g=
mail-ChMk0b"><span class=3D"gmail-ryNqvb">After all, we do already have a r=
eady-made solution in the form of a vacuum, do we?</span></span></span></di=
v><div><span class=3D"gmail-HwtZe" lang=3D"en"><span class=3D"gmail-jCAhz g=
mail-ChMk0b"><span class=3D"gmail-ryNqvb"><br></span></span></span></div><d=
iv><span class=3D"gmail-HwtZe" lang=3D"en"><span class=3D"gmail-jCAhz gmail=
-ChMk0b"><span class=3D"gmail-ryNqvb">If I understand all this=C2=A0</span>=
</span></span>multixact_old.c<span class=3D"gmail-HwtZe" lang=3D"en"><span =
class=3D"gmail-jCAhz gmail-ChMk0b"><span class=3D"gmail-ryNqvb"> machinery =
correctly, in case of </span></span></span>oldestOffsetKnown=3D=3Dfalse</di=
v><div>we should fail with &quot;could not open file&quot; or offset will b=
e 0 in GetOldMultiXactIdSingleMember.</div><div>So, I suppose we can put an=
 analogue of SimpleLruDoesPhysicalPageExist call in the beginning</div><div=
>of=C2=A0GetOldMultiXactIdSingleMember. And if either SimpleLruDoesPhysical=
PageExist return false</div><div>or a corresponding offset will be 0 we hav=
e to bail out with &quot;oldest offset does not exist, consider</div><div>r=
unning vacuum before pg_upgrdade&quot; or smth. Please, correct me if I&#39=
;m wrong.<br></div><div><span class=3D"gmail-HwtZe" lang=3D"en"><span class=
=3D"gmail-jCAhz gmail-ChMk0b"><span class=3D"gmail-ryNqvb"><br></span></spa=
n></span></div></div><span class=3D"gmail_signature_prefix">-- </span><br><=
div dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><div>Best regard=
s,<br></div><div>Maxim Orlov.</div></div></div></div>

--00000000000053263f062b1b254d--