On Thu, Aug 19, 2010 at 12:49:45PM -0400, Robert Haas wrote: > On Thu, Aug 19, 2010 at 11:33 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > Greg Stark <gsst...@mit.edu> writes: > >> On Thu, Aug 19, 2010 at 11:59 AM, Pavel Stehule <pavel.steh...@gmail.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. > > +1. I think the functions are useful, but the perfect is the enemy of the > good.
Percentile is already there as NTILE, a windowing function. Median may be useful, but we pretty much can't just call it "median." Instead, we need to call it something like "left_median" or "arithmetic_median." Cheers, David. -- David Fetter <da...@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fet...@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
