| From: | Neil Conway <neilc(at)samurai(dot)com> |
|---|---|
| To: | "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: qsort again (was Re: [PERFORM] Strange Create Index |
| Date: | 2006-02-16 19:14:03 |
| Message-ID: | 1140117243.31672.54.camel@localhost.localdomain |
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| Lists: | pgsql-hackers pgsql-performance |
On Thu, 2006-02-16 at 12:35 +0100, Steinar H. Gunderson wrote:
> glibc-2.3.5/stdlib/qsort.c:
>
> /* Order size using quicksort. This implementation incorporates
> four optimizations discussed in Sedgewick:
>
> I can't see any references to merge sort in there at all.
stdlib/qsort.c defines _quicksort(), not qsort(), which is defined by
msort.c. On looking closer, it seems glibc actually tries to determine
the physical memory in the machine -- if it is sorting a single array
that exceeds 1/4 of the machine's physical memory, it uses quick sort,
otherwise it uses merge sort.
-Neil
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