Revert b6002a796

This removes "Add Result Cache executor node".  It seems that something
weird is going on with the tracking of cache hits and misses as
highlighted by many buildfarm animals.  It's not yet clear what the
problem is as other parts of the plan indicate that the cache did work
correctly, it's just the hits and misses that were being reported as 0.

This is especially a bad time to have the buildfarm so broken, so
reverting before too many more animals go red.

Discussion: https://postgr.es/m/CAApHDvq_hydhfovm4=izgWs+C5HqEeRScjMbOgbpC-jRAeK3Yw@mail.gmail.com

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -1602,7 +1602,6 @@ SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1) FULL
  20 |  0 | AAA020
 (10 rows)
 
-SET enable_resultcache TO off;
 -- right outer join + left outer join
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 RIGHT JOIN ft2 t2 ON (t1.c1 = t2.c1) LEFT JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
@@ -1629,7 +1628,6 @@ SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 RIGHT JOIN ft2 t2 ON (t1.c1 = t2.c1) LEFT
  20 |  0 | AAA020
 (10 rows)
 
-RESET enable_resultcache;
 -- left outer join + right outer join
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1) RIGHT JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
@@ -2141,25 +2139,22 @@ SELECT t1c1, avg(t1c1 + t2c1) FROM (SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2
 -- join with lateral reference
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM ft1 t2, ft2 t3 WHERE t2.c1 = t3.c1 AND t2.c2 = t1.c2) q ORDER BY t1."C 1" OFFSET 10 LIMIT 10;
-                                                                                   QUERY PLAN                                                                                   
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+                                                                             QUERY PLAN                                                                             
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Limit
    Output: t1."C 1"
    ->  Nested Loop
          Output: t1."C 1"
          ->  Index Scan using t1_pkey on "S 1"."T 1" t1
                Output: t1."C 1", t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7, t1.c8
-         ->  Result Cache
-               Cache Key: t1.c2
-               ->  Subquery Scan on q
-                     ->  HashAggregate
-                           Output: t2.c1, t3.c1
-                           Group Key: t2.c1, t3.c1
-                           ->  Foreign Scan
-                                 Output: t2.c1, t3.c1
-                                 Relations: (public.ft1 t2) INNER JOIN (public.ft2 t3)
-                                 Remote SQL: SELECT r1."C 1", r2."C 1" FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")) AND ((r1.c2 = $1::integer))))
-(16 rows)
+         ->  HashAggregate
+               Output: t2.c1, t3.c1
+               Group Key: t2.c1, t3.c1
+               ->  Foreign Scan
+                     Output: t2.c1, t3.c1
+                     Relations: (public.ft1 t2) INNER JOIN (public.ft2 t3)
+                     Remote SQL: SELECT r1."C 1", r2."C 1" FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")) AND ((r1.c2 = $1::integer))))
+(13 rows)
 
 SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM ft1 t2, ft2 t3 WHERE t2.c1 = t3.c1 AND t2.c2 = t1.c2) q ORDER BY t1."C 1" OFFSET 10 LIMIT 10;
  C 1 

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -502,12 +502,10 @@ SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 FULL JOIN ft2 t2 ON (t1.c1 = t2.c1) LEFT
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1) FULL JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1) FULL JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
-SET enable_resultcache TO off;
 -- right outer join + left outer join
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 RIGHT JOIN ft2 t2 ON (t1.c1 = t2.c1) LEFT JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 RIGHT JOIN ft2 t2 ON (t1.c1 = t2.c1) LEFT JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
-RESET enable_resultcache;
 -- left outer join + right outer join
 EXPLAIN (VERBOSE, COSTS OFF)
 SELECT t1.c1, t2.c2, t3.c3 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1) RIGHT JOIN ft4 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;