Re: Avoid computing ORDER BY junk columns unnecessarily

Agreed.

I haven't looked into these patches, but it seems that there is an issue
with how the targetlist is handled for foreign rels.  The following test
case for postgres_fdw hits the Assert in apply_tlist_labeling().

contrib_regression=# SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1;
server closed the connection unexpectedly

When we create foreign final path in add_foreign_final_paths(), we use
root->upper_targets[UPPERREL_FINAL] as the PathTarget.  This PathTarget
is set in grouping_planner(), without removing the junk columns.  I
think this is why the above query hits the Assert.

Thanks
Richard