On Mon, Oct 11, 2010 at 10:08 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Sun, Oct 10, 2010 at 5:16 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. What I read in SQL:2008 is that >>> percentile_cont is defined for all numeric types (returning >>> approximate numeric with implementation-defined precision), >>> and for interval (returning interval), and not for any other >>> input type. So it appears to me that what we ought to support >>> is >>> median(float8) returns float8 >>> median(interval) returns interval >>> and nothing else --- we can rely on implicit casting to convert >>> any other numeric input type to float8. > >> Isn't there a possibility of a precision loss if numeric gets cast to >> float8? > > So? The standard says "implementation-defined precision". We can > define it as giving results that are good to float8. I find it hard to > imagine an application for median() where that's not good enough; > and what's more, the difference in comparison speed between float8 and > numeric would render median() on numeric pretty useless anyway.
I suppose for most applications it won't matter; I just hate losing precision, and have a deep skepticism of floats, as we've discussed previously. :-) -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
