Re: BUG #17495: Regression in 15beta1 when filtering subquery including row_number window function

On Thu, May 26, 2022 at 6:33 AM David Rowley <dgrowleyml@gmail.com> wrote:

> I think the correct fix is to change remove_unused_subquery_outputs()
> so it also checks the WindowClause runConditions in addition to the
> rel targetlist and baserestrictinfo.
>

Yes, concur with that. Yesterday I played around with a similar patch
which leverages find_window_functions() to locate all the WindowFunc
nodes in runCondition expressions and then check if each WindowFunc
target entry of the subquery is contained there.


> Maybe a better fix is to add a new Bitmapset field to WindowClause and
> have find_window_run_conditions() record the attno in that field when
> it appends the new runCondition to the runCondition field.
> remove_unused_subquery_outputs() can just bms_add_members that field
> to attrs_used.  This just means having to add a field to WindowClause
> post-beta.  Is that going to be a problem?
>

This is even better if we can keep the attnos somewhere for the window
quals that are pushed down to runConditions. Like Tom proposed, maybe
PlannerInfo is a more proper place.

Thanks
Richard