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commit    37bbe3d3acd62bad24493356a98579bd92c8f563
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Fri Feb 23 20:21:53 2024 +0000
First released in: 17.0, 12.19, 13.15, 14.12, 15.7, 16.3

    Avoid dangling-pointer problem with partitionwise joins under GEQO.
    
    build_child_join_sjinfo creates a derived SpecialJoinInfo in
    the short-lived GEQO context, but afterwards the semi_rhs_exprs
    from that may be used in a UniquePath for a child base relation.
    This breaks the expectation that all base-relation-level structures
    are in the planning-lifespan context, leading to use of a dangling
    pointer with probable ensuing crash later on in create_unique_plan.
    To fix, copy the expression trees when making a UniquePath.
    
    Per bug #18360 from Alexander Lakhin.  This has been broken since
    partitionwise joins were added, so back-patch to all supported
    branches.
    
    Discussion: https://postgr.es/m/18360-a23caf3157f34e62@postgresql.org


 src/backend/optimizer/util/pathnode.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 46fd29be832..e5c82bf6878 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1696,8 +1696,13 @@ create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
 	pathnode->path.pathkeys = NIL;
 
 	pathnode->subpath = subpath;
-	pathnode->in_operators = sjinfo->semi_operators;
-	pathnode->uniq_exprs = sjinfo->semi_rhs_exprs;
+
+	/*
+	 * Under GEQO, the sjinfo might be short-lived, so we'd better make copies
+	 * of data structures we extract from it.
+	 */
+	pathnode->in_operators = copyObject(sjinfo->semi_operators);
+	pathnode->uniq_exprs = copyObject(sjinfo->semi_rhs_exprs);
 
 	/*
 	 * If the input is a relation and it has a unique index that proves the


[parent: 90ad85db6a4e]