Horton

Re: On disable_cost

Robert Haas <robertmhaas@gmail.com>

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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: 2024-10-02T14:04:15Z
Lists: pgsql-hackers 
On Wed, Oct 2, 2024 at 4:55 AM David Rowley <dgrowleyml@gmail.com> wrote:
> On Tue, 1 Oct 2024 at 06:17, Laurenz Albe <laurenz.albe@cybertec.at> wrote:
> > Why did you change "Disabled" from an integer to a boolean?
>
> I just don't think "Disabled Nodes" is all that self-documenting and
> I'm also unsure why the full integer value of disabled_nodes is
> required over just displaying the boolean value of if the node is
> disabled or not. Won't readers look at the remainder of the plan to
> determine information about which other nodes are disabled? Do we need
> to give them a running total?

I don't think this will produce the right answer in all cases because
disabled node counts don't propagate across subquery levels.

-- 
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.