Re: On disable_cost

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>, Tom Lane <tgl@sss.pgh.pa.us>, Heikki Linnakangas <hlinnaka@iki.fi>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-10-07T15:14:30Z
Lists: pgsql-hackers
On Sat, Oct 5, 2024 at 1:37 AM David Rowley <dgrowleyml@gmail.com> wrote:
> Thanks for explaining your point of view. I've not shifted my opinion
> any, so I guess we just disagree. I feel a strong enough dislike for
> the current EXPLAIN output to feel it's worth working harder to have a
> better output.
>
> I won't push my point any further unless someone else appears
> supporting Laurenz and I. Thank you for working on getting rid of the
> disabled_cost. I think what we have is now much better than before.
> The EXPLAIN output is the only part I dislike about this work.
>
> I'd encourage anyone else on the sidelines who has an opinion on how
> to display the disabled-ness of a plan node in EXPLAIN to speak up
> now, even if it's just a +1 to something someone has already written.
> It would be nice to see what more people think.

I think you have adequate consensus to proceed with this. I'd just ask
that you don't disappear completely if it turns out that there are
problems. I accept that my commit created this problem and I'm
certainly willing to be involved too if we need to sort out more
things.

-- 
Robert Haas
EDB: http://www.enterprisedb.com



Commits

  1. Doc: add detail about EXPLAIN's "Disabled" property

  2. Adjust EXPLAIN's output for disabled nodes

  3. Fix order of parameters in a cost_sort call

  4. Show number of disabled nodes in EXPLAIN ANALYZE output.

  5. Treat number of disabled nodes in a path as a separate cost metric.

  6. Remove grotty use of disable_cost for TID scan plans.