Re: autovacuum strategy / parameters

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От Robert Haas
Тема Re: autovacuum strategy / parameters
Дата
Msg-id y2g603c8f071004221155h3874a3c0ybbe2c790e3c1bf80@mail.gmail.com
обсуждение исходный текст
Ответ на autovacuum strategy / parameters  (Rick <richard.branton@ca.com>)
Список pgsql-performance
On Wed, Apr 21, 2010 at 11:06 AM, Rick <richard.branton@ca.com> wrote:
> I have a DB with small and large tables that can go up to 15G.
> For performance benefits, it appears that analyze has much less cost
> than vacuum, but the same benefits?

Err, no.  ANALYZE gathers statistics for the query planner; VACUUM
clears out old, dead tuples so that space can be reused by the
database system.

> I can’t find any clear recommendations for frequencies and am
> considering these parameters:
>
> Autovacuum_vacuum_threshold = 50000
> Autovacuum_analyze_threshold = 10000
> Autovacuum_vacuum_scale_factor = 0.01
> Autovacuum_analyze_scale_factor = 0.005
>
> This appears it will result in table analyzes occurring around 10,000
> to 85,000 dead tuples and vacuum occuring around 50,000 to 200,000,
> depending on the table sizes.
>
> Can anyone comment on whether this is the right strategy and targets
> to use?

I'm not that familiar with tuning these parameters but increasing the
default thesholds by a thousand-fold doesn't seem like a good idea.
Small tables will never get vacuumed or analyzed at all.

...Robert

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