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

On Thu, May 26, 2022 at 11:47 AM David Rowley <dgrowleyml@gmail.com> wrote:

The problem is that the qual pushdown stuff all happens in
set_subquery_pathlist() before we call subquery_planner() for the
subquery.  We don't yet have a PlannerInfo made for the subquery when
we call check_and_push_window_quals().  We don't really have any other
means to communicate to subquery_planner() what the run conditions are
for the given Query object. Plus, we *do* really need to know what the
runConditions are before we call subquery_planner() so that those
conditions can be properly tagged onto WindowAggPaths. I don't really
think it would be right to pluck those from the PlannerInfo when we
later call create_plan(). That wouldn't leave us any opportunity to do
any costing related stuff with run conditions if we decide to do that
later.

The remove_unused_subquery_outputs() also happens before we call
subquery_planner() for the subquery. Cann't we just store the attnos
used in window quals that are pushed down to runConditions in the
PlannerInfo of the upper query?