Re: A couple of p.tches for PostgreSQL 64bit support

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>
Cc: postgres(at)cybertec(dot)at, pgsql-patches(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Koichi Suzuki <koichi(at)intellilink(dot)co(dot)jp>, Satoshi Nagayasu <nagayasus(at)nttdata(dot)co(dot)jp>, ikubo(at)intellilink(dot)co(dot)jp, yasunaga <yasunaga(dot)hisato(at)soft(dot)fujitsu(dot)com>, Bruce Momjian <root(at)candle(dot)pha(dot)pa(dot)us>, Jan Wieck <JanWieck(at)Yahoo(dot)com>, sakata(dot)tetsuo(at)lab(dot)ntt(dot)co(dot)jp, "T(dot)Honishi" <honishi(dot)takashi(at)lab(dot)ntt(dot)co(dot)jp>
Subject: Re: A couple of p.tches for PostgreSQL 64bit support
Date: 2005-07-08 02:37:04
Message-ID: 20050708023704.GA29807@alvh.no-ip.org
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On Fri, Jul 08, 2005 at 09:38:07AM +0900, ITAGAKI Takahiro wrote:
> Hans-J|rgen Schvnig <postgres(at)cybertec(dot)at> wrote:
>
> > 64-bit XIDs seem to be an overkill - the only practical impact I can see
> > is an even larger tuple header (this can be an issue on large boxes too
> > - at least compared to Oracle).
>
> I agreed, too. The changes of XIDs cannot be ignored because the overhead
> will be 32bytes per tuple.
>
> Avoiding overheads, can XIDs/CIDs be different bit length? For example,
> can XIDs/CIDs be changed to 48/16-bit or 40/24-bit?

Not unless you change the definition of HeapTupleFields
(src/include/access/htup.h). Alignment concerns would probably bite you
if you changed it, anyway.

--
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"Ninguna manada de bestias tiene una voz tan horrible como la humana" (Orual)

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