2010/10/12 Hitoshi Harada <umi.tan...@gmail.com>: > 2010/10/12 Pavel Stehule <pavel.steh...@gmail.com>: >> Hello >> >> 2010/10/11 Greg Stark <gsst...@mit.edu>: >>> On Sun, Oct 10, 2010 at 2:16 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>>> It was pointed out upthread that while median isn't presently >>>> in the standard, Oracle defines it in terms of percentile_cont(0.5) >>>> which *is* in the standard. >>> >>> Uhmm, then why don't we implement that? We could provide median() as a >>> short-cut but percentile_cont() doesn't sound much harder to implement >>> than median() and more general. >> >> The problem is in interface. The original patch did it, but I removed >> it. We cannot to unsure immutability of some parameters now. Can we >> enhance a AGGREGATE to allow some mark like IMMUTABLE parameter and >> probably we should to support ANSI syntax: >> >> PERCENTILE_CONT ( expression1 ) >> WITHIN GROUP ( ORDER BY expression2 [ ASC | DESC ] ) >> >> This syntax allows to divide a muttable and immutable parameters. > > If this is only a syntax sugar for mutable/immutable parameter, then I > guess it's time to take it serious to implement in our syntax, > although I'm not sure if it affects more execution model than > interface.
I though about it, the question is an interface for PL languages. There are not problem for C. Regards Pavel Stehule > > Regards, > > > > -- > Hitoshi Harada > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
