2009/8/14 Олег Царев <zabivator@gmail.com>:
> 2009/8/14 Hitoshi Harada <umi.tanuki@gmail.com>:
>> 2009/8/14 Pavel Stehule <pavel.stehule@gmail.com>:
>>> 2009/8/13 Hitoshi Harada <umi.tanuki@gmail.com>:
>>>> 2009/8/14 Pavel Stehule <pavel.stehule@gmail.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)
>
I thing, so you are afraid too much about memory. Look on current
postgres. Any hash grouping is faster than sort grouping. Try and see.
PostgreSQL isn't embeded database. So there are not main goal an using
less memory. The goal is has features with clean, readable and
maintainable source code.
