Re: proposal: tuplestore, tuplesort aggregate functions

2010/8/18 Tom Lane <tgl@sss.pgh.pa.us>:
> Pavel Stehule <pavel.stehule@gmail.com> writes:
>> I still thinking about a "median" type functions. My idea is to
>> introduce a new syntax for stype definition - like
>
>> stype = type, or
>> stype = ARRAY OF type [ ORDER [ DESC | ASC ]], or
>> stype = TUPLESTORE OF type, or
>> stype = TUPLESORT OF type [ DESC | ASC ]
>
> This seems like a fairly enormous amount of conceptual (and code)
> infrastructure just to make it possible to build median() out of spare
> parts.  It's also exposing some implementation details that I'd just as
> soon not expose in SQL.  I'd rather just implement median as a
> special-purpose aggregate.

yes, it is little bit strange - but when we talked last time about
this topic, I understand, so you dislike any special solution for this
functionality. So I searched different more general way. On the other
hand, I agree so special purpose aggregate (with a few changes in
nodeAgg) can be enough. The median (and additional forms) is really
special and there are not wide used use case.

Regards

Pavel


>
>                        regards, tom lane
>