| From: | Matheus de Oliveira <matioli(dot)matheus(at)gmail(dot)com> |
|---|---|
| To: | bkrug <bkrug(at)usatech(dot)com> |
| Cc: | pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Avoiding Refreezing XIDs Repeatedly |
| Date: | 2015-02-09 16:48:17 |
| Message-ID: | CAJghg4KAFiFnH6inJ+K7Bfef9bgGYt7E6MM3rkevqiT=Q245HQ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Mon, Feb 9, 2015 at 1:58 PM, bkrug <bkrug(at)usatech(dot)com> wrote:
> Couldn't postgres reserve a special XID that is never available for normal
> transactions but that indicates that any transaction can see it because it
> is so old? Then instead of constantly having to freeze old XIDs each time
> the XID is going to wrap, vacuum can just set it to the special XID and
> never touch it again unless something really changes.
>
It changed in recent versions (9.3 or 9.4, I don't recall exactly which)
and moved to tuple header, but what you described is exactly what was done,
the xid was 2.
Anyway, an already frozen tuple won't be "re-frozen" again.
Regards,
--
Matheus de Oliveira
Analista de Banco de Dados
Dextra Sistemas - MPS.Br nível F!
www.dextra.com.br/postgres
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