| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: Turning off HOT/Cleanup sometimes |
| Date: | 2015-04-20 21:49:18 |
| Message-ID: | 20150420214918.GU11720@momjian.us |
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| Lists: | pgsql-hackers |
On Mon, Apr 20, 2015 at 09:56:20PM +0100, Simon Riggs wrote:
> On 20 April 2015 at 20:28, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>
>
> But why should 1 SELECT or 20 SELECTs or 200 SELECTs have to do a job,
> while the user waits, which is fundamentally VACUUM's duty to do in the
> background?
>
>
> Agreed. I don't see a % as giving us anything at all.
>
> The idea is that we want to turn an O(N) problem for one query into an O(1)
> task.
>
>
> The use case I see for this is when there is a mixed workload. There is
> one select which reads the entire table, and hundreds of thousands of
> selects/updates/insert that don't, and of course vacuum comes along every
> now and then and does it thing. Why should the one massive SELECT have
> horrible performance just because it was run right before autovacuum would
> have kicked in instead of right after if finished?
>
>
> +1
You can +1 all you want, but if you ignore the specific workloads I
mentioned, you are not going to get much traction.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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