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Re: More thoughts about planner's cost estimates

From: Jim Nasby <jnasby(at)pervasive(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, Hannu Krosing <hannu(at)skype(dot)net>, "Todd A(dot)Cook" <tcook(at)blackducksoftware(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: More thoughts about planner's cost estimates
Date: 2006-06-05 13:29:56
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Jun 4, 2006, at 5:09 PM, Tom Lane wrote:

> Greg Stark <gsstark(at)mit(dot)edu> writes:
>> Hannu Krosing <hannu(at)skype(dot)net> writes:
>>> Ühel kenal päeval, L, 2006-06-03 kell 10:43, kirjutas Jim Nasby:
>>>> Might also be worth adding analyze delay settings, ala
>>>> vacuum_cost_delay.
> ANALYZE already respects the vacuum delay settings.
>>> Actually we should have delay settings for all potential
>>> (almost-)full-scan service ops, - VACUUM, ANALYSE, CREATE INDEX, ADD
>>> CONSTRAINT, maybe more - so that there would be better chances of
>>> running those on busy databases without disastrous effects.
>> What about UPDATE and DELETE and for that matter SELECT?
> This seems pretty silly.  The point of the delay stuff is to prevent
> background maintenance operations from eating an unreasonable share
> of resources compared to foreground queries.  I don't see why you'd
> put delays into queries --- if your machine is loaded, it's loaded.

'maintenance operations' often also mean running large updates. Being  
able to run those at a reduced priority would certainly be helpful in  
many cases. Though, a better way to accomplish this would be to have  
the OS handle prioritized IO scheduling, but since pretty much none  
of them seem to do that...
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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