From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Josh Berkus <josh(at)agliodbs(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Rick <richard(dot)branton(at)ca(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: autovacuum strategy / parameters |
Date: | 2010-05-01 03:08:20 |
Message-ID: | 20100501030820.GI3151@alvh.no-ip.org |
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Thread: | |
Lists: | pgsql-performance |
Josh Berkus escribió:
> #autovacuum_vacuum_scale_factor = 0.2
>
> This is set because in my experience, 20% bloat is about the level at
> which bloat starts affecting performance; thus, we want to vacuum at
> that level but not sooner. This does mean that very large tables which
> never have more than 10% updates/deletes don't get vacuumed at all until
> freeze_age; this is a *good thing*. VACUUM on large tables is expensive;
> you don't *want* to vacuum a billion-row table which has only 100,000
> updates.
Hmm, now that we have partial vacuum, perhaps we should revisit this.
> It would be worth doing a DBT2/DBT5 test run with different autovac
> settings post-8.4 so see if we should specifically change the vacuum
> threshold.
Right.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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