Re: [BUGS] BUG #14890: Error grouping by same column twice using FDW

+            /*
+             * Pushable, add to tlist. We need to create a tle for this
+             * expression and need to transfer the sortgroupref too. We cannot
+             * use add_to_flat_tlist() here as it avoids the duplicate entries
+             * in the targetlist but here we want those duplicate entries as
+             * there can be multiple GROUP BY expressions pointing to the same
+             * column at different positions.
+             */
+            tle = makeTargetEntry((Expr *) expr, list_length(tlist) + 1, NULL,
+                                  false);
+            tle->ressortgroupref = sgref;
+            tlist = lappend(tlist, tle);

May be we want to use add_flat_to_tlist() when sgref is not present to avoid
duplicate entries.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company