Fix test case for 'outer pathkeys do not match mergeclauses' fix.

Commit 4bbf6edf added a test case,
but it turns out that the test case doesn't reliably test for the
bug, and in the context of the regression test suite did not because
ANALYZE had not been run.

Report and patch by Etsuro Fujita.  I added a comment along lines
previously suggested by Tom Lane.

Discussion: http://postgr.es/m/5A6195D8.8060206@lab.ntt.co.jp

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -560,11 +560,16 @@ SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5
 SELECT ft5, ft5.c1, ft5.c2, ft5.c3, ft4.c1, ft4.c2 FROM ft5 left join ft4 on ft5.c1 = ft4.c1 WHERE ft4.c1 BETWEEN 10 and 30 ORDER BY ft5.c1, ft4.c1;
 
 -- multi-way join involving multiple merge joins
+-- (this case used to have EPQ-related planning problems)
+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.c1 = ft4.c1
-    AND ft1.c1 = ft5.c1 FOR UPDATE;
-SELECT * FROM ft1, ft2, ft4, ft5 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = ft4.c1
-    AND ft1.c1 = ft5.c1 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 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;
+RESET enable_nestloop;
+RESET enable_hashjoin;
 
 -- check join pushdown in situations where multiple userids are involved
 CREATE ROLE regress_view_owner SUPERUSER;