Fix LATERAL join test in test memoize.sql

The test in question was meant to be testing Memoize to ensure it worked
correctly when the inner side of the join contained lateral vars, however,
nothing in the lateral subquery stopped it from being pulled up into the
main query, so the planner did that, and that meant no more lateral vars.

Here we add a simple ORDER BY to stop the planner from being able to
pullup the lateral subquery.

Author: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4_LHJaN4L-tXpKMiPFnsCJWU1P8Xh59o0W7AA6UN99=cQ@mail.gmail.com
Backpatch-through: 14, where Memoize was added.

src/test/regress/expected/memoize.out

@@ -63,7 +63,8 @@ WHERE t2.unique1 < 1000;
 -- Try with LATERAL joins
 SELECT explain_memoize('
 SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
-LATERAL (SELECT t2.unique1 FROM tenk1 t2 WHERE t1.twenty = t2.unique1) t2
+LATERAL (SELECT t2.unique1 FROM tenk1 t2
+         WHERE t1.twenty = t2.unique1 ORDER BY 1) t2
 WHERE t1.unique1 < 1000;', false);
                                       explain_memoize                                      
 -------------------------------------------------------------------------------------------
@@ -74,7 +75,7 @@ WHERE t1.unique1 < 1000;', false);
                Rows Removed by Filter: 9000
          ->  Memoize (actual rows=1 loops=N)
                Cache Key: t1.twenty
-               Cache Mode: logical
+               Cache Mode: binary
                Hits: 980  Misses: 20  Evictions: Zero  Overflows: 0  Memory Usage: NkB
                ->  Index Only Scan using tenk1_unique1 on tenk1 t2 (actual rows=1 loops=N)
                      Index Cond: (unique1 = t1.twenty)
@@ -83,7 +84,8 @@ WHERE t1.unique1 < 1000;', false);
 
 -- And check we get the expected results.
 SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
-LATERAL (SELECT t2.unique1 FROM tenk1 t2 WHERE t1.twenty = t2.unique1) t2
+LATERAL (SELECT t2.unique1 FROM tenk1 t2
+         WHERE t1.twenty = t2.unique1 ORDER BY 1) t2
 WHERE t1.unique1 < 1000;
  count |        avg         
 -------+--------------------

src/test/regress/sql/memoize.sql

@@ -47,12 +47,14 @@ WHERE t2.unique1 < 1000;
 -- Try with LATERAL joins
 SELECT explain_memoize('
 SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
-LATERAL (SELECT t2.unique1 FROM tenk1 t2 WHERE t1.twenty = t2.unique1) t2
+LATERAL (SELECT t2.unique1 FROM tenk1 t2
+         WHERE t1.twenty = t2.unique1 ORDER BY 1) t2
 WHERE t1.unique1 < 1000;', false);
 
 -- And check we get the expected results.
 SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
-LATERAL (SELECT t2.unique1 FROM tenk1 t2 WHERE t1.twenty = t2.unique1) t2
+LATERAL (SELECT t2.unique1 FROM tenk1 t2
+         WHERE t1.twenty = t2.unique1 ORDER BY 1) t2
 WHERE t1.unique1 < 1000;
 
 -- Reduce work_mem and hash_mem_multiplier so that we see some cache evictions