| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com> |
| Cc: | 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 14:40:27 |
| Message-ID: | 19876.1306680027@sss.pgh.pa.us |
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=?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.
regards, tom lane
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