| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | "Dann Corbit" <DCorbit(at)connx(dot)com>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, "Jerry Sievers" <jerry(at)jerrysievers(dot)com> |
| Subject: | Re: qsort, once again |
| Date: | 2006-03-21 20:37:35 |
| Message-ID: | 19857.1142973455@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Greg Stark <gsstark(at)mit(dot)edu> writes:
> That looks better both on average and in the worst case. Are the time
> constants that much worse that the merge sort still takes longer?
Keep in mind that this is only counting the number of
comparison-function calls; it's not accounting for any other effects.
In particular, for a large sort operation quicksort might win because of
its more cache-friendly memory access patterns.
The whole question of our qsort vs the system library's qsort probably
needs to be revisited, however, now that we've identified and fixed this
particular performance issue.
regards, tom lane
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