| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Kevin Grittner <kgrittn(at)ymail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: autovacuum not prioritising for-wraparound tables |
| Date: | 2013-02-01 15:17:25 |
| Message-ID: | 20130201151725.GD4918@alvh.no-ip.org |
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| Lists: | pgsql-hackers |
Andres Freund wrote:
> If youre careful you can also notice that there is an interesting typo
> in the freeze table computation. Namely it uses freeze_min_age instead
> of freeze_table_age. Which probably explains why I had so bad
> performance results with lowering vacuum_freeze_min_age, it basically
> radically increases the amount of full-table-scans, far more than it
> should.
>
> I can't imagine that anybody with a large database ran pg successfully
> with a small freeze_min_age due to this.
>
> It seems to be broken since the initial introduction of freeze_table_age
> in 6587818542e79012276dcfedb2f97e3522ee5e9b. I guess it wasn't noticed
> because the behaviour is only visible via autovacuum because a
> user-issued VACUUM passes -1 as freeze_min_age.
Backpatched all the way back to 8.4
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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