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

On Mon, Jan 20, 2014 at 8:42 PM, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> On Mon, Jan 20, 2014 at 2:45 PM, Florian Pflug <fgp(at)phlo(dot)org> wrote:
>
>> * EXPLAIN VERBOSE ANALYZE now shows the max. number of forward aggregate
>> transitions per row and aggregate. It's a bit imprecise, because it
>> doesn't
>> track the count per aggregate, but it's still a good metric for how well
>> the inverse transition functions work. If the number is close to one,
>> you
>> know that very few rescans are happening.
>>
>>
> I've not looked at this yet and I don't think I'll have time tonight, but
> it sounds interesting. I guess it might be quite nice to have a way to see
> this especially with the way the numeric stuff works, it might be actually
> pretty hard to otherwise know how many inverse transition "failures" there
> had been. Do you think it's also worth tracking the inverse transition
> failures too?
>
>
I've merged this patch but I attempted to get it into a bit more of a ready
state by moving the code out into a helper function the same way as the
other explain stuff is done. I've not touched explain before so do let me
know if I've made it worse.

https://github.com/david-rowley/postgres/commits/invtrans

Regards

David Rowley