| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Noah Misch <noah(at)leadboat(dot)com> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Marti Raudsepp <marti(at)juffo(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thom Brown <thom(at)linux(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: B-Tree support function number 3 (strxfrm() optimization) |
| Date: | 2014-08-07 08:09:22 |
| Message-ID: | CAM3SWZQiGvGhMB4TMbEWoNjO17=ySB5b5Y5MGqJsaNq4uWTryA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Aug 6, 2014 at 10:36 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> This *almost* applies to patched Postgres if you pick a benchmark that
> is very sympathetic to my patch. To my surprise, work_mem = '10MB'
> (which results in an external tape sort) is sometimes snapping at the
> heels of a work_mem = '5GB' setting (which results in an in-memory
> quicksort).
Note that this was with a default temp_tablespaces setting that wrote
temp files on my home partition/SSD. With a /dev/shm/ temp tablespace,
tape sort edges ahead, and has a couple of hundred milliseconds on
quicksort for this test case. It's actually faster.
--
Peter Geoghegan
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