Fix Memoize to work with partitionwise joining.

A couple of places weren't up to speed for this.  By sheer good
luck, we didn't fail but just selected a non-memoized join plan,
at least in the test case we have.  Nonetheless, it's a bug,
and I'm not quite sure that it couldn't have worse consequences
in other examples.  So back-patch to v14 where Memoize came in.

Richard Guo

Discussion: https://postgr.es/m/CAMbWs48GkNom272sfp0-WeD6_0HSR19BJ4H1c9ZKSfbVnJsvRg@mail.gmail.com

5 files changed, 63 insertions, 3 deletions

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 2a3f0ab7bfc..4d09881259c 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -597,7 +597,8 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
 	/* Check if we have hash ops for each parameter to the path */
 	if (paraminfo_get_equal_hashops(root,
 									inner_path->param_info,
-									outerrel,
+									outerrel->top_parent ?
+									outerrel->top_parent : outerrel,
 									innerrel,
 									&param_exprs,
 									&hash_operators,
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 5379c087a1f..55deee555ae 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -4246,6 +4246,7 @@ do { \
 
 				FLAT_COPY_PATH(mpath, path, MemoizePath);
 				REPARAMETERIZE_CHILD_PATH(mpath->subpath);
+				ADJUST_CHILD_ATTRS(mpath->param_exprs);
 				new_path = (Path *) mpath;
 			}
 			break;
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index dbaa9bb54dc..12624e6adb1 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1865,8 +1865,8 @@ typedef struct MemoizePath
 {
 	Path		path;
 	Path	   *subpath;		/* outerpath to cache tuples from */
-	List	   *hash_operators; /* hash operators for each key */
-	List	   *param_exprs;	/* cache keys */
+	List	   *hash_operators; /* OIDs of hash equality ops for cache keys */
+	List	   *param_exprs;	/* expressions that are cache keys */
 	bool		singlerow;		/* true if the cache entry is to be marked as
 								 * complete after caching the first record. */
 	bool		binary_mode;	/* true when cache key should be compared bit
diff --git a/src/test/regress/expected/memoize.out b/src/test/regress/expected/memoize.out
index 00438eb1ea0..de43afa76ed 100644
--- a/src/test/regress/expected/memoize.out
+++ b/src/test/regress/expected/memoize.out
@@ -197,6 +197,45 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
 (8 rows)
 
 DROP TABLE strtest;
+-- Ensure memoize works with partitionwise join
+SET enable_partitionwise_join TO on;
+CREATE TABLE prt (a int) PARTITION BY RANGE(a);
+CREATE TABLE prt_p1 PARTITION OF prt FOR VALUES FROM (0) TO (10);
+CREATE TABLE prt_p2 PARTITION OF prt FOR VALUES FROM (10) TO (20);
+INSERT INTO prt VALUES (0), (0), (0), (0);
+INSERT INTO prt VALUES (10), (10), (10), (10);
+CREATE INDEX iprt_p1_a ON prt_p1 (a);
+CREATE INDEX iprt_p2_a ON prt_p2 (a);
+ANALYZE prt;
+SELECT explain_memoize('
+SELECT * FROM prt t1 INNER JOIN prt t2 ON t1.a = t2.a;', false);
+                                     explain_memoize                                      
+------------------------------------------------------------------------------------------
+ Append (actual rows=32 loops=N)
+   ->  Nested Loop (actual rows=16 loops=N)
+         ->  Index Only Scan using iprt_p1_a on prt_p1 t1_1 (actual rows=4 loops=N)
+               Heap Fetches: N
+         ->  Memoize (actual rows=4 loops=N)
+               Cache Key: t1_1.a
+               Cache Mode: logical
+               Hits: 3  Misses: 1  Evictions: Zero  Overflows: 0  Memory Usage: NkB
+               ->  Index Only Scan using iprt_p1_a on prt_p1 t2_1 (actual rows=4 loops=N)
+                     Index Cond: (a = t1_1.a)
+                     Heap Fetches: N
+   ->  Nested Loop (actual rows=16 loops=N)
+         ->  Index Only Scan using iprt_p2_a on prt_p2 t1_2 (actual rows=4 loops=N)
+               Heap Fetches: N
+         ->  Memoize (actual rows=4 loops=N)
+               Cache Key: t1_2.a
+               Cache Mode: logical
+               Hits: 3  Misses: 1  Evictions: Zero  Overflows: 0  Memory Usage: NkB
+               ->  Index Only Scan using iprt_p2_a on prt_p2 t2_2 (actual rows=4 loops=N)
+                     Index Cond: (a = t1_2.a)
+                     Heap Fetches: N
+(21 rows)
+
+DROP TABLE prt;
+RESET enable_partitionwise_join;
 -- Exercise Memoize code that flushes the cache when a parameter changes which
 -- is not part of the cache key.
 -- Ensure we get a Memoize plan
diff --git a/src/test/regress/sql/memoize.sql b/src/test/regress/sql/memoize.sql
index 0979bcdf768..17c5b4bfab5 100644
--- a/src/test/regress/sql/memoize.sql
+++ b/src/test/regress/sql/memoize.sql
@@ -104,6 +104,25 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
 
 DROP TABLE strtest;
 
+-- Ensure memoize works with partitionwise join
+SET enable_partitionwise_join TO on;
+
+CREATE TABLE prt (a int) PARTITION BY RANGE(a);
+CREATE TABLE prt_p1 PARTITION OF prt FOR VALUES FROM (0) TO (10);
+CREATE TABLE prt_p2 PARTITION OF prt FOR VALUES FROM (10) TO (20);
+INSERT INTO prt VALUES (0), (0), (0), (0);
+INSERT INTO prt VALUES (10), (10), (10), (10);
+CREATE INDEX iprt_p1_a ON prt_p1 (a);
+CREATE INDEX iprt_p2_a ON prt_p2 (a);
+ANALYZE prt;
+
+SELECT explain_memoize('
+SELECT * FROM prt t1 INNER JOIN prt t2 ON t1.a = t2.a;', false);
+
+DROP TABLE prt;
+
+RESET enable_partitionwise_join;
+
 -- Exercise Memoize code that flushes the cache when a parameter changes which
 -- is not part of the cache key.