Horton

Re: [HACKERS] Autovacuum Improvements

Heikki Linnakangas <heikki@enterprisedb.com>

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From: Heikki Linnakangas <heikki@enterprisedb.com>
To: Russell Smith <mr-russ@pws.com.au>
Cc: Darcy Buskermolen <darcyb@commandprompt.com>, Simon Riggs <simon@2ndquadrant.com>, Alvaro Herrera <alvherre@commandprompt.com>, "Matthew T. O'Connor" <matthew@zeut.net>, Pavan Deolasee <pavan@enterprisedb.com>, Christopher Browne <cbbrowne@acm.org>, pgsql-general@postgresql.org, pgsql-hackers@postgresql.org
Date: 2007-01-22T11:21:41Z
Lists: 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