From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Peter Geoghegan <pg(at)heroku(dot)com> |
Cc: | Rod Taylor <rod(dot)taylor(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: A worst case for qsort |
Date: | 2014-08-08 12:54:31 |
Message-ID: | CA+TgmobewrKKHG6wPovAmS3EZH+3kvD7Wv2uBWyiyyVbuzhidw@mail.gmail.com |
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Lists: | pgsql-hackers |
On Thu, Aug 7, 2014 at 5:52 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> 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, ...
Well, I'm not sure why you're having a hard time imagining it.
Presorted input is a common case in general; that's why we have a
check for it. That check adds overhead in the non-pre-sorted case to
improve the pre-sorted case, and nobody's ever argued for removing it
that I can recall.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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