Re: POC: GROUP BY optimization

On 22/1/2022 01:34, Tomas Vondra wrote:
> The other thing we could do is reduce the coefficient gradually - so 
> it'd be 1.5 for the first pathkey, then 1.25 for the next one, and so 
> on. But it seems somewhat arbitrary (I certainly don't have some sound 
> theoretical justification ...).

I think, it hasn't a reason to increase complexity without any theory at 
the bottom. Simple solution allows to realize problems much faster, if 
they arise.

> ... I've skipped the path_save 
> removal in planner.c, because that seems incorrect - if there are 
> multiple pathkeys, we must start with the original path, not the 
> modified one we built in the last iteration. Or am I missing something
You are right, I misunderstood the idea of path_save variable.

-- 
regards,
Andrey Lepikhov
Postgres Professional