Horton

Re: On disable_cost

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Alexander Lakhin <exclusion@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-09-06T09:27:22Z
Lists: pgsql-hackers 
On Fri, Sep 6, 2024 at 5:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
> static void
> label_sort_with_costsize(PlannerInfo *root, Sort *plan, double limit_tuples)
> {
> ...
>      cost_sort(&sort_path, root, NIL,
>                lefttree->total_cost,
>                plan->plan.disabled_nodes,
>                lefttree->plan_rows,
>                lefttree->plan_width,
>                0.0,
>                work_mem,
>                limit_tuples);
>
> Given the cost_sort() declaration:
> void
> cost_sort(Path *path, PlannerInfo *root,
>            List *pathkeys, int input_disabled_nodes,
>            Cost input_cost, double tuples, int width,
>            Cost comparison_cost, int sort_mem,
>            double limit_tuples)
>
> Aren't the input_disabled_nodes and input_cost arguments swapped in the
> above call?

Nice catch!  I checked other callers to cost_sort, and they are all
good.

(I'm a little surprised that this does not cause any plan diffs in the
regression tests.)

Thanks
Richard

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.