Re: Implementation of GROUPING SETS (T431: Extended grouping capabilities)

2009/8/14 Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>:
> 2009/8/14 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:
>> 2009/8/13 Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>:
>>> 2009/8/14 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:
>>>> I prefered using CTE, because this way was the most short to small
>>>> bugs less prototype - with full functionality.
>>>
>>> You could make it by query rewriting, but as you say the best cleanest
>>> way is total refactoring of existing nodeAgg. How easy to implement is
>>> not convincing.
>>>
>>
>> I agree. Simply I am not have time and force do it. I would to
>> concentrate on finishing some plpgsql issues, and then I have to do
>> some other things than PostgreSQL. There are fully functional
>> prototype and everybody is welcome to continue in this work.
>>
>
> I see your situation. Actually your prototype is good shape to be
> discussed in both ways. But since you've been focusing on this feature
> it'd be better if you keep your eyes on this.
>
> So, Oleg, do you continue on this?
>
>
> Regards,
>
>
> --
> Hitoshi Harada
>

> I'd imagine such like:
>
> select a, b, count(*) from x group by rollup(a, b);
>
> PerGroup all = init_agg(), a = init_agg(), ab = init_agg();
> while(row = fetch()){
> if(group_is_changed(ab, row)){
> result_ab = finalize_agg(ab);
> ab = init_agg();
> }
> if(group_is_changed(a, row)){
> result_a = finalize_agg(a);
> a = init_agg();
> }
> advance_agg(all, row);
> advance_agg(a, row);
> advance_agg(ab, row);
> }
> result_all = finalize_agg(all);
Fun =) My implementation of rollup in DBMS qd work as your imagine there! =)
Also, multiply sort of source we take for CUBE implementation, but
this hard for support (sort in group by - it's bloat).
As result we have merge implementation of group by, rollup, and window
functions with some common code - it's way for grouping of source,
Hash implementation group xxx on different hash-tables (with different
keys) it's very expensive (require many memory for keys).
I hope continue my work, after end of time trouble on work =( (bad
TPC-H perfomance)