v5-0001-Disable-push-down-FETCH-FIRST-WITH-TIES-clause-efujita.patch

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 078b8a966f..ea566d5034 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -1047,6 +1047,27 @@ SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2 order by t1.c2 limit 1;
   1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1          | foo
 (1 row)
 
+-- Ensure we don't ship FETCH FIRST .. WITH TIES
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT t1.c2 FROM ft1 t1 WHERE t1.c1 > 960 ORDER BY t1.c2 FETCH FIRST 2 ROWS WITH TIES;
+                                           QUERY PLAN                                            
+-------------------------------------------------------------------------------------------------
+ Limit
+   Output: c2
+   ->  Foreign Scan on public.ft1 t1
+         Output: c2
+         Remote SQL: SELECT c2 FROM "S 1"."T 1" WHERE (("C 1" > 960)) ORDER BY c2 ASC NULLS LAST
+(5 rows)
+
+SELECT t1.c2 FROM ft1 t1 WHERE t1.c1 > 960 ORDER BY t1.c2 FETCH FIRST 2 ROWS WITH TIES;
+ c2 
+----
+  0
+  0
+  0
+  0
+(4 rows)
+
 -- Test CASE pushdown
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT c1,c2,c3 FROM ft2 WHERE CASE WHEN c1 > 990 THEN c1 END < 1000 ORDER BY c1;
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 4053cd641c..a343f4372d 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -7140,6 +7140,20 @@ add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
 	if (ifpinfo->local_conds)
 		return;
 
+	/*
+	 * If the query uses FETCH FIRST .. WITH TIES, 1) it must have ORDER BY as
+	 * well, which is used to determine which additional rows tie for the last
+	 * place in the result set, and 2) ORDER BY must already have been
+	 * determined to be safe to push down before we get here.  So in that case
+	 * the FETCH clause is safe to push down with ORDER BY if the remote
+	 * server is v13 or later, but if not, the remote query will fail entirely
+	 * for lack of support for it.  Since we do not currently have a way to do
+	 * a remote-version check (without accessing the remote server), disable
+	 * pushing the FETCH clause for now.
+	 */
+	if (parse->limitOption == LIMIT_OPTION_WITH_TIES)
+		return;
+
 	/*
 	 * Also, the LIMIT/OFFSET cannot be pushed down, if their expressions are
 	 * not safe to remote.
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 09ba234e43..b57f8cfda6 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -408,6 +408,11 @@ EXPLAIN (VERBOSE, COSTS OFF)
   SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2 order by t1.c2 limit 1;
 SELECT * FROM ft1 t1 WHERE t1.c1 === t1.c2 order by t1.c2 limit 1;
 
+-- Ensure we don't ship FETCH FIRST .. WITH TIES
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT t1.c2 FROM ft1 t1 WHERE t1.c1 > 960 ORDER BY t1.c2 FETCH FIRST 2 ROWS WITH TIES;
+SELECT t1.c2 FROM ft1 t1 WHERE t1.c1 > 960 ORDER BY t1.c2 FETCH FIRST 2 ROWS WITH TIES;
+
 -- Test CASE pushdown
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT c1,c2,c3 FROM ft2 WHERE CASE WHEN c1 > 990 THEN c1 END < 1000 ORDER BY c1;