From: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>, Greg Stark <gsstark(at)mit(dot)edu>, Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Florian Helmberger <fh(at)25th-floor(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum |
Date: | 2011-05-29 15:48:42 |
Message-ID: | BANLkTi=ONrsOoMD3rOdPjRnKPrirKE+fpg@mail.gmail.com |
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On Sun, May 29, 2011 at 8:10 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> =?ISO-8859-1?Q?C=E9dric_Villemain?= <cedric(dot)villemain(dot)debian(at)gmail(dot)com> writes:
>> 2011/5/29 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>>> OK, do you like the attached version of that logic? (Other fragments
>>> of the patch as before.)
>
>> The idea was that remove only one page from the VACUUM will prevent
>> relfrozenxid update and reltuples (and relpages) update.
>> Now, I beleive that once we've skip at least one page thanks to
>> SKIP_PAGES_THRESHOLD, then we should be more agressive and remove as
>> many as possible pages from the VACUUM, tks to the VM.
>
> That would require proof, not just suggestion. Skipping pages will
> defeat the OS read-ahead algorithm, and so could easily cost more than
> reading them.
>
My worry is what we have right now is also based on just assumptions
and gut feelings rather than any numbers.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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