From: | Peter Geoghegan <pg(at)heroku(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
Subject: | Re: Using quicksort for every external sort run |
Date: | 2015-11-22 23:40:40 |
Message-ID: | CAM3SWZS71RR0RLUYD5PEc-R4rC=mpwQpXGSqxgfd2xoRq3mP9g@mail.gmail.com |
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On Fri, Nov 20, 2015 at 2:58 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> The numbers speak for themselves here. I just want to be clear about
> the disadvantages of what I propose, even if it's well worth it
> overall in most (all?) cases.
There is a paper called "Critical Evaluation of Existing External
Sorting Methods in the Perspective of Modern Hardware":
http://ceur-ws.org/Vol-1343/paper8.pdf
This paper was not especially influential, and I don't agree with
every detail, or I at least don't think that every recommendation
should be adopted to Postgres. Even still, the paper is the best
summary I have seen so far. It clearly explains why there is plenty to
recommend a simple hybrid sort-merge strategy over replacement
selection, despite the fact that replacement selection is faster when
using 1970s hardware.
--
Peter Geoghegan
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