Horton

Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum

Pavan Deolasee <pavan.deolasee@gmail.com>

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From: Pavan Deolasee <pavan.deolasee@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Cédric Villemain <cedric.villemain.debian@gmail.com>, Greg Stark <gsstark@mit.edu>, Robert Haas <robertmhaas@gmail.com>, Kevin Grittner <Kevin.Grittner@wicourts.gov>, Florian Helmberger <fh@25th-floor.com>, Alvaro Herrera <alvherre@commandprompt.com>, pgsql-hackers@postgresql.org
Date: 2011-05-29T15:48:42Z
Lists: pgsql-hackers 
On Sun, May 29, 2011 at 8:10 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> =?ISO-8859-1?Q?C=E9dric_Villemain?= <cedric.villemain.debian@gmail.com> writes:
>> 2011/5/29 Tom Lane <tgl@sss.pgh.pa.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