From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Interesting glitch in autovacuum |
Date: | 2008-09-10 17:40:25 |
Message-ID: | 20080910174025.GI4399@alvh.no-ip.org |
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Thread: | |
Lists: | pgsql-hackers |
Tom Lane wrote:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Tom Lane wrote:
> >> Lastly, now that we have the PROC_IN_VACUUM test in GetSnapshotData,
> >> is it actually necessary for lazy vacuum to avoid setting a snapshot?
> >> It seems like it might be a good idea for it to do so in order to
> >> keep its RecentGlobalXmin reasonably current.
>
> > Hmm, I think I'd rather be inclined to get a snapshot just when it's
> > going to finish.
>
> I'm worried about keeping RecentGlobalXmin up to date during the
> vacuums, not only at the end, because it will be used for HOT page
> pruning during the vacuums.
Oh, I see. I didn't know we were doing HOT pruning during vacuum; does
it make sense?
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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