Whilst fooling with my outer-join-aware-Vars patch, I tripped
across a multi-way join query that failed with
ERROR: could not devise a query plan for the given query
when enable_partitionwise_join is on.
I traced that to the fact that reparameterize_path_by_child()
omits support for MaterialPath, so that if the only surviving
path(s) for a child join include materialization steps, we'll
fail outright to produce a plan for the parent join.
Unfortunately, I don't have an example that produces such a
failure against HEAD. It seems certain to me that such cases
exist, though, so I'd like to apply and back-patch the attached.
I'm suspicious now that reparameterize_path() should be
extended likewise, but I don't really have any hard
evidence for that.
regards, tom lane
commit f74ca5d8611af3306eb96719d5d1910c9b6a8db5
Author: Tom Lane <t...@sss.pgh.pa.us>
Date: Thu Dec 1 21:04:49 2022 -0500
Add missing MaterialPath case in reparameterize_path_by_child.
Surprised we hadn't noticed this already.
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index c77399ca92..224ba84107 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -4209,6 +4209,16 @@ do { \
}
break;
+ case T_MaterialPath:
+ {
+ MaterialPath *mpath;
+
+ FLAT_COPY_PATH(mpath, path, MaterialPath);
+ REPARAMETERIZE_CHILD_PATH(mpath->subpath);
+ new_path = (Path *) mpath;
+ }
+ break;
+
case T_MemoizePath:
{
MemoizePath *mpath;
