Re: proposal: tuplestore, tuplesort aggregate functions

On Thu, Aug 19, 2010 at 06:03:57PM -0400, Robert Haas wrote:
> On Thu, Aug 19, 2010 at 5:53 PM, David Fetter <david(at)fetter(dot)org> wrote:
> > On Thu, Aug 19, 2010 at 05:40:46PM -0400, Tom Lane wrote:
> >> "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> >> > Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> >> >> I suppose there could also be a bit of an ambiguity if you're working
> >> >> with a type like int4 where the values are discrete steps.  Like, what
> >> >> do you do with {1, 2}?
> >>
> >> Hmm, good point.
> >>
> >> > The same thing you do with the avg function?
> >>
> >> avg's approach is not at all datatype-independent though.  If
> >> you're willing to give up the idea of a polymorphic median()
> >> function, that would probably be the thing to do.  If not, you
> >> need to take the left or right one of the two central elements.
> >
> > Whether the median needs to be in the sample is one question that
> > doesn't really have a universal right answer.  A separate
> > question, also without a universal right answer, is whether the
> > median needs to be in the same domain as the sample, int4 being
> > the case above.
> >
> > We could just go with "whatever Oracle, DB2 and MS-SQL Server
> > have," assuming it's the same thing, until something appears in
> > the SQL standard.
>
> That's usually a sensible default, when in doubt. If nothing else,
> it improves compatibility.

That's assuming we find such a thing, which I haven't yet.

Trying to stay cheery,
David.
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