Re: Avoid extra Sort nodes between WindowAggs when sorting can be reused

> On 27 Jul 2018, at 21:12, Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru> wrote:

> Thanks for the update.

Thank you for reviewing and hacking!

> On 07/25/2018 01:37 AM, Daniel Gustafsson wrote:
>> 
>>> Hmm, this is missing the eqop fields of SortGroupClause. I haven't
>>> tested yet but does the similar degradation happen if two
>>> SortGroupCaluses have different eqop and the same other values?
>> I wasn’t able to construct a case showing this, but I also think you’re right.
>> Do you have an idea of a query that can trigger a regression?  The attached
>> patch adds a stab at this, but I’m not sure if it’s the right approach.
> 
> To trigger that, in your test example you could order by empno::int8 for one window, and by empno::int2 for another. But don't I think you have to compare eqop here, because if eqop differs, sortop will differ too. I removed the comparison from the patch.

Right, that makes sense.

> I also clarified (I hope) the comments, and did the optimization I mentioned earlier: using array instead of list for active clauses. Please see the attached v6.

Thanks, looks good.

> Otherwise I think the patch is good.

Cool, thanks for reviewing!

cheers ./daniel