Re: [HACKERS] [PATCH] Negative Transition Aggregate Functions (WIP)

[David Rowley]

On Tue, Jan 14, 2014 at 9:09 PM, David Rowley <dgrowle...@gmail.com> wrote:

> I think unless anyone has some objections I'm going to remove the inverse
> transition for SUM(numeric) and modify the documents to tell the user how
> to build their own FAST_SUM(numeric) using the built in functions to do it.
> I'm starting to think that playing around with resetting numeric scale will
> turn a possible 9.4 patch into a 9.5/10.0 patch. I see no reason why what's
> there so far, minus sum(numeric), can't go in...
>
>
Of course its only now that I discover that this is not possible to do this:

CREATE AGGREGATE fast_sum (numeric)
(
    stype = numeric,
    sfunc = numeric_avg_accum,
    invfunc = numeric_avg_accum_inv,
    finalfunc = numeric_sum
);

because SUM(numeric) uses an internal type to store the transition state.

hmmm, built-in fast_sum anyone?
Is there any simple way to limit these to only be used in the context of a
window? If so is it worth it?
Would we want fast_sum() for float too?

Regards

David Rowley