Re: Skipping logical replication transactions on subscriber side

From: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Euler Taveira <euler(at)eulerto(dot)com>, "osumi(dot)takamichi(at)fujitsu(dot)com" <osumi(dot)takamichi(at)fujitsu(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, "tanghy(dot)fnst(at)fujitsu(dot)com" <tanghy(dot)fnst(at)fujitsu(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Greg Nancarrow <gregn4422(at)gmail(dot)com>, "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com>, Alexey Lesovsky <lesovsky(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Skipping logical replication transactions on subscriber side
Date: 2022-04-04 01:28:30
Message-ID: CAD21AoAGXsn0XaKNybjurc7D9h=0hBibSLLixCLwB1EyWarR=w@mail.gmail.com
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On Sun, Apr 3, 2022 at 9:45 AM Noah Misch <noah(at)leadboat(dot)com> wrote:
>
> On Sat, Apr 02, 2022 at 08:44:45PM +0900, Masahiko Sawada wrote:
> > On Sat, Apr 2, 2022 at 7:04 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > On Sat, Apr 2, 2022 at 1:43 PM Noah Misch <noah(at)leadboat(dot)com> wrote:
> > > > Some options:
> > > > - Move subskiplsn after subdbid, so it's always aligned anyway. I've
> > > > confirmed that this lets the test pass, in 44s.
> > > > - Move subskiplsn to the CATALOG_VARLEN section, despite its fixed length.
> > >
> > > +1 to any one of the above. I mildly prefer the first option as that
> > > will allow us to access the value directly instead of going via
> > > SysCacheGetAttr but I am fine either way.
> >
> > +1. I also prefer the first option.
>
> Sounds good to me.

I've attached the patch for the first option.

> - Introduce a new typalign value suitable for uint64. This is more intrusive,
> but it's more future-proof. Looking beyond catalog columns, it might
> improve performance by avoiding unaligned reads.

The third option would be a good item for PG16 or later.

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/

Attachment Content-Type Size
make_subskiplsn_aligned.patch application/octet-stream 1.3 KB

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