| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
| Cc: | Russell Smith <mr-russ(at)pws(dot)com(dot)au>, Darcy Buskermolen <darcyb(at)commandprompt(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>, Pavan Deolasee <pavan(at)enterprisedb(dot)com>, Christopher Browne <cbbrowne(at)acm(dot)org>, pgsql-general(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] Autovacuum Improvements |
| Date: | 2007-01-22 15:30:09 |
| Message-ID: | 200701221530.l0MFU9019849@momjian.us |
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| Lists: | pgsql-general pgsql-hackers |
Heikki Linnakangas wrote:
> Russell Smith wrote:
> > 2. Index cleanup is the most expensive part of vacuum. So doing a
> > partial vacuum actually means more I/O as you have to do index cleanup
> > more often.
>
> I don't think that's usually the case. Index(es) are typically only a
> fraction of the size of the table, and since 8.2 we do index vacuums in
> a single scan in physical order. In fact, in many applications the index
> is be mostly cached and the index scan doesn't generate any I/O at all.
Are _all_ the indexes cached? I would doubt that. Also, for typical
table, what percentage is the size of all indexes combined?
--
Bruce Momjian bruce(at)momjian(dot)us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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