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Re: a heavy duty operation on an "unused" table kills my server

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Eduardo Piombino <drakorg(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org
Subject: Re: a heavy duty operation on an "unused" table kills my server
Date: 2010-01-17 23:00:21
Message-ID: 4B539685.40703@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-performance
Eduardo Piombino wrote:
> In the case where priority inversion is not to be used, I would 
> however still greatly benefit from the slow jobs/fast jobs mechanism, 
> just being extra-careful that the slow jobs, obviously, did not 
> acquire any locks that a fast job would ever require. This alone would 
> be, still, a *huge* feature if it was ever to be introduced, 
> reinforcing the real-time awareness/requirements, that many 
> applications look for  today.

In this context, "priority inversion" is not a generic term related to 
running things with lower priorities.  It means something very 
specific:  that you're allowing low-priority jobs to acquire locks on 
resources needed by high-priority ones, and therefore blocking the 
high-priority ones from running effectively.  Unfortunately, much like 
deadlock, it's impossible to avoid the problem in a generic way just by 
being careful.  It's one of the harder issues that needs to be 
considered in order to make progress on implementing this feature one day.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com  www.2ndQuadrant.com


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Next:From: Tom LaneDate: 2010-01-17 23:14:38
Subject: Re: a heavy duty operation on an "unused" table kills my server
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