| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Nathan Boley <npboley(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>, "jd(at)commandprompt(dot)com" <jd(at)commandprompt(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Vladimir Sitnikov <sitnikov(dot)vladimir(at)gmail(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: benchmarking the query planner |
| Date: | 2008-12-12 18:15:00 |
| Message-ID: | 200812121815.mBCIF0Z10383@momjian.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera wrote:
> Robert Haas escribi?:
> > > Which raises the issue, if we could get better statistics by passing
> > > the whole table, why not do that when VACUUM ANALYZE is run?
> >
> > I think the reason is "because the next autovacuum would undo it".
>
> Is there any way to "merge" the statistics? i.e. if a full table scan
> is done to compute precise statistics, and later a regular analyze scan
> is done, then perhaps instead of clobbering the previous stats, you
> merge them with the new ones, thus not completely losing those previous
> ones.
Crazy idea, but if a partial analyze finds that 5% of the table has
changed since the last full analyze, but 10% of the statistics are
different, we know something is wrong. ;-)
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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