| From: | Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu> |
|---|---|
| To: | Dann Corbit <DCorbit(at)connx(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Luke Lonergan <llonergan(at)greenplum(dot)com>, Neil Conway <neilc(at)samurai(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Re: Which qsort is used |
| Date: | 2005-12-17 06:13:07 |
| Message-ID: | Pine.LNX.4.58.0512170104330.3394@eon.cs |
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| Lists: | pgsql-hackers |
On Sat, 17 Dec 2005, Dann Corbit wrote:
>
> The benchmarks say that they (order checks) are a good idea on average
> for ordered data, random data, and partly ordered data.
>
I interpret that in linux, 5000000 seems a divide for qsortpdq. Before
that number, it wins, after that, bsd wins more. On SunOS, qsortpdq takes
the lead till the last second -- I suspect this is due to the rand()
function:
Linux - #define RAND_MAX 2147483647
SunOS - #define RAND_MAX 32767
So in SunOS, the data actually not that scattered - so more favourate for
sorted() or reversed() check?
Regards,
Qingqing
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