Re: BUG #19037: Planner fails on estimating array length with "no relation entry" error

On Mon, Sep 1, 2025 at 11:57 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm slightly tempted to do the dirty work in cost_subplan() itself,
> ie pass a NULL down to cost_qual_eval from there. Right now it
> doesn't matter, but maybe in future there would be some other
> safer use for the parent root in cost_subplan()?

Fair point.

> This approach
> would force the same behavior for the third caller of cost_subplan,
> SS_make_initplan_from_plan. But I don't think it matters there,
> since an initplan will by definition not be consulting anything from
> the parent plan.

Yeah, it should be safe to use a NULL root for initplans. Besides, in
the case of SS_make_initplan_from_plan, testexpr will be NULL, and
cost_qual_eval() becomes a no-op.

Here is the patch that passes root as NULL to cost_qual_eval() in
cost_subplan(), along with some commentary about why.

- Richard