Fix broken MemoizePath support in reparameterize_path().

It neglected to recurse to the subpath, meaning you'd get back
a path identical to the input.  This could produce wrong query
results if the omission meant that the subpath fails to enforce
some join clause it should be enforcing.  We don't have a test
case for this at the moment, but the code is obviously broken
and the fix is equally obvious.  Back-patch to v14 where
Memoize was introduced.

Richard Guo

Discussion: https://postgr.es/m/CAMbWs4_R=ORpz=Lkn2q3ebPC5EuWyfZF+tmfCPVLBVK5W39mHA@mail.gmail.com

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index ea2e158f6d428d458c10a612d12e5e53b7979317..5379c087a1f0173383b1a0a8c70fc7f163e6fe99 100644 (file)
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3994,9 +3994,15 @@ reparameterize_path(PlannerInfo *root, Path *path,
        case T_Memoize:
            {
                MemoizePath *mpath = (MemoizePath *) path;
+               Path       *spath = mpath->subpath;
 
+               spath = reparameterize_path(root, spath,
+                                           required_outer,
+                                           loop_count);
+               if (spath == NULL)
+                   return NULL;
                return (Path *) create_memoize_path(root, rel,
-                                                   mpath->subpath,
+                                                   spath,
                                                    mpath->param_exprs,
                                                    mpath->hash_operators,
                                                    mpath->singlerow,