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In-Reply-To: <ff143b24-a093-40da-9833-d36b83726bdf@iki.fi>
From: wenhui qiu <qiuwenhuifx@gmail.com>
Date: Tue, 23 Apr 2024 21:03:06 +0800
Message-ID: <CAGjGUAKO1GCzG5wBMt5RosWo0PatgFpYY=Gjgt77tN2brNe=Bg@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Maxim Orlov <orlovmg@gmail.com>, 
	Postgres hackers <pgsql-hackers@lists.postgresql.org>
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Hi Maxim Orlov
   Thank you so much for your tireless work on this. Increasing the WAL
size by a few bytes should have very little impact with today's disk
performance(Logical replication of this feature wal log is also increased a
lot, logical replication is a milestone new feature, and the community has
been improving the logical replication of functions),I believe removing
troubled postgresql Transaction ID Wraparound was also a milestone  new
feature  adding a few bytes is worth it!

Best regards

On Tue, 23 Apr 2024 at 17:37, Heikki Linnakangas <hlinnaka@iki.fi> wrote:

> On 23/04/2024 11:23, Maxim Orlov wrote:
> > PROPOSAL
> > Make multixact offsets 64 bit.
>
> +1, this is a good next step and useful regardless of 64-bit XIDs.
>
> > @@ -156,7 +148,7 @@
> >               ((uint32) ((0xFFFFFFFF % MULTIXACT_MEMBERS_PER_PAGE) + 1))
> >
> >  /* page in which a member is to be found */
> > -#define MXOffsetToMemberPage(xid) ((xid) / (TransactionId)
> MULTIXACT_MEMBERS_PER_PAGE)
> > +#define MXOffsetToMemberPage(xid) ((xid) / (MultiXactOffset)
> MULTIXACT_MEMBERS_PER_PAGE)
> >  #define MXOffsetToMemberSegment(xid) (MXOffsetToMemberPage(xid) /
> SLRU_PAGES_PER_SEGMENT)
> >
> >  /* Location (byte offset within page) of flag word for a given member */
>
> This is really a bug fix. It didn't matter when TransactionId and
> MultiXactOffset were both typedefs of uint32, but it was always wrong.
> The argument name 'xid' is also misleading.
>
> I think there are some more like that, MXOffsetToFlagsBitShift for example.
>
> --
> Heikki Linnakangas
> Neon (https://neon.tech)
>
>
>
>

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<div dir=3D"ltr">Hi Maxim Orlov<br>=C2=A0 =C2=A0Thank you so much for your =
tireless work on this.=C2=A0Increasing the WAL size by a few bytes should h=
ave very little impact with today&#39;s disk performance(Logical replicatio=
n of this feature wal log is also increased a lot, logical replication is a=
 milestone new feature, and the community has been improving the logical re=
plication of functions),I believe removing troubled postgresql Transaction =
ID Wraparound was also a milestone=C2=A0=C2=A0new feature=C2=A0=C2=A0adding=
 a few bytes is worth it!<br><br>Best regards<br></div><br><div class=3D"gm=
ail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, 23 Apr 2024 at 17:=
37, Heikki Linnakangas &lt;<a href=3D"mailto:hlinnaka@iki.fi">hlinnaka@iki.=
fi</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margi=
n:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex=
">On 23/04/2024 11:23, Maxim Orlov wrote:<br>
&gt; PROPOSAL<br>
&gt; Make multixact offsets 64 bit.<br>
<br>
+1, this is a good next step and useful regardless of 64-bit XIDs.<br>
<br>
&gt; @@ -156,7 +148,7 @@<br>
&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0((uint32) ((0xFF=
FFFFFF % MULTIXACT_MEMBERS_PER_PAGE) + 1))<br>
&gt;=C2=A0 <br>
&gt;=C2=A0 /* page in which a member is to be found */<br>
&gt; -#define MXOffsetToMemberPage(xid) ((xid) / (TransactionId) MULTIXACT_=
MEMBERS_PER_PAGE)<br>
&gt; +#define MXOffsetToMemberPage(xid) ((xid) / (MultiXactOffset) MULTIXAC=
T_MEMBERS_PER_PAGE)<br>
&gt;=C2=A0 #define MXOffsetToMemberSegment(xid) (MXOffsetToMemberPage(xid) =
/ SLRU_PAGES_PER_SEGMENT)<br>
&gt;=C2=A0 <br>
&gt;=C2=A0 /* Location (byte offset within page) of flag word for a given m=
ember */<br>
<br>
This is really a bug fix. It didn&#39;t matter when TransactionId and <br>
MultiXactOffset were both typedefs of uint32, but it was always wrong. <br>
The argument name &#39;xid&#39; is also misleading.<br>
<br>
I think there are some more like that, MXOffsetToFlagsBitShift for example.=
<br>
<br>
-- <br>
Heikki Linnakangas<br>
Neon (<a href=3D"https://neon.tech" rel=3D"noreferrer" target=3D"_blank">ht=
tps://neon.tech</a>)<br>
<br>
<br>
<br>
</blockquote></div>

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