Re: foreign join error "variable not found in subplan target list"

On Mon, Aug 29, 2022 at 5:45 PM Richard Guo <guofenglinux@gmail.com> wrote:

>
> On Mon, Aug 29, 2022 at 2:17 PM Etsuro Fujita <etsuro.fujita@gmail.com>
> wrote:
>
>> One thing I noticed while re-reading the patch is that we should use
>> create_projection_path() here, to avoid modifying the epq_path in
>> place, as it is already used for an unsorted join-pushdown path before
>> we get here.  So I modified the patch as such.  Updated patch
>> attached.
>
>
> The new change looks reasonable to me as there is other ref to this
> epq_path.
>
> I'm looking again on how we adjust the PathTarget, and I think we may
> need to update the cost and width fields if there are any new columns
> added. Maybe we can leverage set_pathtarget_cost_width for that.
>

To be concrete, I mean something like this:

--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -5808,6 +5808,10 @@ add_paths_with_pathkeys_for_rel(PlannerInfo *root,
RelOptInfo *rel,

                                      PVC_RECURSE_PLACEHOLDERS));
                }

+               /* Update the cost and width fields if we have added any
new columns. */
+               if (!equal(epq_path->pathtarget->exprs, target->exprs))
+                       set_pathtarget_cost_width(root, target);
+
                /*
                 * The passed-in EPQ path is a join path, so it is
projection-capable,
                 * but we use create_projection_path() here, so as to avoid
modifying


Thanks
Richard