Re: On disable_cost

On Thu, 2024-10-03 at 11:44 +1300, David Rowley wrote:
> 2) Laurenz is misunderstanding what "Disabled Nodes" means. It has
> nothing to do with other Paths which were considered and rejected. It
> might be better named as "Disabled Degree". It tracks how many plan
> nodes below and including this node are disabled.
>
> Because of #2, I think I now understand why Laurenz was interested in
> only showing this with VERBOSE. If it worked the way Laurenz thought,
> I'd probably agree with him.

Ah, thanks, now I see the light.
You only see a "disabled node" if the optimizer chose a node you explicitly
disabled, like a sequential scan, a nested loop join or a sort.

I completely agree with you: it should always be displayed, and a boolean is
the appropriate way.  The display just shouldn't be propagated up the tree
to nodes that were not actually disabled.

Perhaps a line of documentation on the EXPLAIN reference page or on the
"Using EXPLAIN" page would be in order.

Yours,
Laurenz Albe