Re: On disable_cost

On Sun, 6 Oct 2024 at 06:29, Alena Rybakina <a.rybakina@postgrespro.ru> wrote:
> > On 04.10.2024 00:52, David Rowley wrote:
> >  Append
> >    ->  Index Only Scan using lp1_a_idx on lp1 lp_1
> >    ->  Sort
> >          Disabled: true
> >          Sort Key: lp_2.a
> >          ->  Seq Scan on lp2 lp_2

> To be honest, I don’t understand at all why we don’t count disabled nodes for append here? As I understand it, this
isdue to the fact that the partitioned table can also be scanned by an index. Besides mergeappend, in general it’s
difficultfor me to generalize for which nodes this rule applies, can you explain here? 

There are no special rules here of what to display based on the node
type. Maybe you think there are some special rules because of the
special cases for Append and MergeAppend in the patch? Those are
handled specially as they don't use the Plan's lefttree and righttree
fields.

Are you saying that the "Disabled: true" should propagate to the root
of the plan tree?  That fact that master does that is what Laurenz and
I are complaining about. I'm not sure if I follow what you're asking.

David