From: | Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com> |
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To: | John Naylor <johncnaylorls(at)gmail(dot)com> |
Cc: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru> |
Subject: | Re: [PoC] Improve dead tuple storage for lazy vacuum |
Date: | 2024-04-08 12:42:01 |
Message-ID: | CALT9ZEH11NYV8AOzKb1bWhCf6J0H=H31f0MgT9xX+HdqvcA1rw@mail.gmail.com |
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On Mon, 8 Apr 2024 at 16:27, John Naylor <johncnaylorls(at)gmail(dot)com> wrote:
> On Sun, Apr 7, 2024 at 9:08 AM John Naylor <johncnaylorls(at)gmail(dot)com>
> wrote:
> >
> > I've attached a mostly-polished update on runtime embeddable values,
> > storing up to 3 offsets in the child pointer (1 on 32-bit platforms).
> > As discussed, this includes a macro to cap max possible offset that
> > can be stored in the bitmap, which I believe only reduces the valid
> > offset range for 32kB pages on 32-bit platforms. Even there, it allows
> > for more line pointers than can possibly be useful. It also splits
> > into two parts for readability. It would be committed in two pieces as
> > well, since they are independently useful.
>
> I pushed both of these and see that mylodon complains that anonymous
> unions are a C11 feature. I'm not actually sure that the union with
> uintptr_t is actually needed, though, since that's not accessed as
> such here. The simplest thing seems to get rid if the union and name
> the inner struct "header", as in the attached.
>
Provided uintptr_t is not accessed it might be good to get rid of it.
Maybe this patch also need correction in this:
+#define NUM_FULL_OFFSETS ((sizeof(uintptr_t) - sizeof(uint8) -
sizeof(int8)) / sizeof(OffsetNumber))
Regards,
Pavel
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