Re: median and percentile function implementation

Hello

very nice! I tested it and works very well.

And I looking for implementation in core.

Two notes:

* should to support string_agg and array_agg

Regards

Pavel

2013/8/26 Vik Fearing <vik(dot)fearing(at)dalibo(dot)com>

> On 08/26/2013 02:39 PM, Pavel Stehule wrote:
> > Hello
> >
> > Three years ago we worked on implementation of median function.
> >
> >
> http://www.postgresql.org/message-id/AANLkTimRksUOgGsK7-gTXnvJJGL-1QvuqxidusZQwep6@mail.gmail.com
> >
> >
> > Can we implement this function now?
> >
> > There are a few opened questions:
> >
> > * immutable parameters of aggregate functions
> >
> > * effective implementation when data are in memory
> >
> > * effective implementation when data are out of memory
> >
> > * effective implementation for usage as window function - running median.
> >
> > Better than before, we can choose between hashing and sorting based
> > aggregation. But tuplesort implementation is not right for using as
> > window function. Second issue can be a not possible reusing of
> > tuplesort for more final functions - median, percentile in one query.
> >
> > Ideas how to solve this task? Can we move forward in some points?
>
> Take a look at the standard-compliant WITHIN GROUP that is currently in
> development for 9.4.
>
> http://www.postgresql.org/message-id/2b8b55b8ba82f83ef4e6070b95fb0cd0@news-out.riddles.org.uk
>
> --
> Vik
>
>