| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PATCH] Incremental sort |
| Date: | 2017-04-26 17:20:29 |
| Message-ID: | CAH2-WznmEo2OsBqRb37e9rYFUWk05AQjUNUFL6-UMm4AD=E=sg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Apr 26, 2017 at 10:10 AM, Alexander Korotkov
<a(dot)korotkov(at)postgrespro(dot)ru> wrote:
> OK, I get it. Our qsort is so fast not only on 100% presorted case.
> However, that doesn't change many things in context of incremental sort.
The important point is to make any presorted test case only ~99%
presorted, so as to not give too much credit to the "high risk"
presort check optimization.
The switch to insertion sort that we left in (not the bad one removed
by a3f0b3d -- the insertion sort that actually comes from the B&M
paper) does "legitimately" make sorting faster with presorted cases.
--
Peter Geoghegan
VMware vCenter Server
https://www.vmware.com/
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