Re: proposal: tuplestore, tuplesort aggregate functions

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.

Cheers,
David.
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