| From: | "Dann Corbit" <DCorbit(at)connx(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu>, "Luke Lonergan" <llonergan(at)greenplum(dot)com>, "Neil Conway" <neilc(at)samurai(dot)com>, "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Which qsort is used |
| Date: | 2005-12-14 03:46:36 |
| Message-ID: | D425483C2C5C9F49B5B7A41F8944154757D36C@postal.corporate.connx.com |
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| Lists: | pgsql-hackers |
> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Tuesday, December 13, 2005 7:38 PM
> To: Dann Corbit
> Cc: Qingqing Zhou; Luke Lonergan; Neil Conway; Bruce Momjian; pgsql-
> hackers(at)postgresql(dot)org
> Subject: Re: [HACKERS] Which qsort is used
>
> "Dann Corbit" <DCorbit(at)connx(dot)com> writes:
> > The in-order check happens only once
>
> Hm? What about that call inside qloop's loop?
You're right. Once per partition of size 50 or greater.
In my tests, it was a clear win. We'll see in the Qingqing Zhou test
setup if it helps or not. If there is some order to the data, it will
be of benefit. For purely random samples, there will be a small fixed
cost.
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