| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, David Fetter <david(at)fetter(dot)org> |
| Subject: | Re: wip: functions median and percentile |
| Date: | 2010-08-19 15:33:13 |
| Message-ID: | 4308.1282231993@sss.pgh.pa.us |
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| Lists: | pgsql-hackers pgsql-rrreviewers |
Greg Stark <gsstark(at)mit(dot)edu> writes:
> On Thu, Aug 19, 2010 at 11:59 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>> I am sending a prototype implementation of functions median and
>> percentile. This implementation is very simple and I moved it to
>> contrib for this moment - it is more easy maintainable. Later I'll
>> move it to core.
> So if the entire result set fits in memory it would be nice to use the
> O(n) Quickselect algorithm -- which would only be a small change to
> the existing Quicksort code -- instead of sorting the entire set.
That seems like rather a lot of added infrastructure for functions whose
popularity is at best unknown. I think we should KISS for the first
implementation.
regards, tom lane
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