| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | Russell Smith <mr-russ(at)pws(dot)com(dot)au> |
| Cc: | 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 11:21:41 |
| Message-ID: | 45B49E45.9000504@enterprisedb.com |
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| Thread: | |
| Lists: | pgsql-general pgsql-hackers |
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.
I believe the heap scans are the biggest issue at the moment.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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