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List:       postgresql-general
Subject:    Re: [HACKERS] New 9.6 external sort guidance around temp_tablespaces and maintenance_work_mem
From:       Bruce Momjian <bruce () momjian ! us>
Date:       2016-04-30 23:41:33
Message-ID: 20160430234133.GH556 () momjian ! us
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On Sat, Apr 30, 2016 at 04:39:22PM -0700, Peter Geoghegan wrote:
> On Sat, Apr 30, 2016 at 4:26 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > On Sat, Apr 30, 2016 at 04:23:00PM -0700, Peter Geoghegan wrote:
> >> Maybe there is a place to emphasize this change in the release notes.
> >> I don't really want to make it about the external sort feature,
> >> though, because enabling higher work_mem settings by making sure that
> >> does not disadvantage external sorts is as much about enabling
> >> HashAggregates as it is about enabling internal sorts.
> >
> > We do often mention in the release notes areas that will need retuning.
> 
> How do you feel about it in this instance?
> 
> As you may have gathered, my perspective is that the external sorting
> patches were more about fixing a problem with tuplesort than about
> improving its performance. The performance characteristics of the old
> approach to sorting runs were all over the place, which made
> increasing work_mem like taking one step forward, then two steps
> backwards.

Yes, we should mention something.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I. As I am, so you will be. +
+                     Ancient Roman grave inscription +


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