postgres_fdw: Modify regression tests for EPQ-related planning problems.

This prevents the tests added by commit 4bbf6edf and adjusted by
commit 99f6a17d from being useless by plan changes created by an
upcoming commit.

Author: Etsuro Fujita
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -559,15 +559,19 @@ SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5
 
 -- multi-way join involving multiple merge joins
 -- (this case used to have EPQ-related planning problems)
+CREATE TABLE local_tbl (c1 int NOT NULL, c2 int NOT NULL, c3 text, CONSTRAINT local_tbl_pkey PRIMARY KEY (c1));
+INSERT INTO local_tbl SELECT id, id % 10, to_char(id, 'FM0000') FROM generate_series(1, 1000) id;
+ANALYZE local_tbl;
 SET enable_nestloop TO false;
 SET enable_hashjoin TO false;
 EXPLAIN (VERBOSE, COSTS OFF)
-SELECT * FROM ft1, ft2, ft4, ft5 WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1
-    AND ft1.c2 = ft5.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
-SELECT * FROM ft1, ft2, ft4, ft5 WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1
-    AND ft1.c2 = ft5.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
+SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1
+    AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
+SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1
+    AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 < 100 FOR UPDATE;
 RESET enable_nestloop;
 RESET enable_hashjoin;
+DROP TABLE local_tbl;
 
 -- check join pushdown in situations where multiple userids are involved
 CREATE ROLE regress_view_owner SUPERUSER;