On Wed, Aug 18, 2010 at 04:46:57PM +0200, Pavel Stehule wrote: > 2010/8/18 Tom Lane <t...@sss.pgh.pa.us>: > > David Fetter <da...@fetter.org> writes: > >> Apart from the medians, which "median-like" aggregates do you > >> have in mind to start with? If you can provide examples of > >> "median-like" aggregates that people might need to implement as > >> user-defined aggregates, or other places where people would use > >> this machinery, it will make your case stronger for this > >> refactoring. > > > > There would be plenty of scope to re-use the machinery without any > > SQL-level extensions. All you need is a polymorphic aggregate > > transition function that maintains a tuplestore or whatever. I > > don't see that extra syntax in CREATE AGGREGATE is really buying > > much of anything. > > > > Have we to use a transisdent function? If we implement median as > special variant of aggregate - because we need to push an sort, then > we can skip a transident function function - and call directly final > function. This mechanism is used for aggregates with ORDER BY now. > So there can be a special path for direct call of final func. There > is useles to call transident function.
Just a wacky idea here. Could we make a special state transition function called IDENTITY or some such that would turn into a noop? 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