| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Jan Wieck <JanWieck(at)yahoo(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Russell Smith <mr-russ(at)pws(dot)com(dot)au>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Idea for getting rid of VACUUM FREEZE on cold pages |
| Date: | 2010-06-09 16:49:43 |
| Message-ID: | AANLkTilIKnm29dEoAEhWtt6kE1NxnWUVZ0bg-fqTRAbI@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jun 9, 2010 at 12:09 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> If you
>> freeze all tuples by the time the pages are marked all-visible,
>> perhaps via the xmin-preserving mechanism Simon suggested, then you
>> can use the visibility map to skip anti-wraparound vacuum as well as
>> regular vacuum. That sounds to me like it's accomplishing something.
>> Is it a complete solution? No. Is it better than what we have now?
>> Yes.
>
> I do like the idea of using a status bit rather than FrozenXid to mark a
> frozen tuple, because that eliminates the conflict between wanting to
> freeze aggressively for performance reasons and wanting to preserve Xids
> for forensic reasons. But it doesn't seem to do much for Josh's
> original problem.
OK, I see. So maybe we add a Todo to implement that, and then keep
thinking about how to fix Josh's problem.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company
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