Re: introduction of WIP window function patch

2008/7/5 Martijn van Oosterhout <kleptog@svana.org>:
> On Sat, Jul 05, 2008 at 07:04:29PM +0900, H.Harada wrote:
>> Hi,
>>
>> As I proposed a month before, I am working on window function.
>
> Very nice!
>
>> http://umitanuki.net/pgsql/wfv01/design.html
>>
>> The problem is, as written in the "Things to discussed" section of the
>> document, how you define window functions (e.g. RANK()). My idea is to
>> treat them as specialized functions such as SET OF functions and mark
>> it in pg_proc. But this doesn't resolve RANK() boundary problem.
>
> Actually, I would make RANK() and ROW_NUMBER() act more like
> aggregates. ISTM you have two kinds of window functions:
>
> - aggregation: a result is calculated over a set and the result copied
>  across all the rows.
> - order depenadant: same as above, but the result is different for each
>  row.

So I agree the definition of these two types.

> I think you could make the latter work using the current aggregation
> setup, just by calling the final_func for each row rather than just
> once at the end.

How do you know which type of two above is used in the same SQL syntax?


-- 
Hitoshi Harada