| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Rod Taylor <rod(dot)taylor(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: A worst case for qsort |
| Date: | 2014-08-07 21:52:17 |
| Message-ID: | CAM3SWZR2R-ypWzJ=YpdKPKmchFe4xxgFmCYqPi86L=D9D0=x2g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Aug 7, 2014 at 2:34 PM, Rod Taylor <rod(dot)taylor(at)gmail(dot)com> wrote:
> This one is frequently sorted as batch operations against the files are
> performed in alphabetical order to reduce conflict issues that a random
> ordering may cause between jobs.
Sure. There are cases out there. But, again, I have a hard time
imagining why you'd expect those to be pre-sorted in practice, and
particularly why you'd feel justified in expecting that to sort much
faster than equivalent though slightly imperfectly correlated data.
Without that, the fmgr-elision aspect of sort support appears to offer
enough for us to still win on balance [1], assuming 9.4 is our basis
of comparison.
[1] http://www.postgresql.org/message-id/CAM3SWZQHjxiyrsqBs5w3u-vTJ_jT2hp8o02big5wYb4m9Lp1jg@mail.gmail.com
--
Peter Geoghegan
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