diff -U3 /tmp/cirrus-ci-build/src/test/regress/expected/join.out /tmp/cirrus-ci-build/src/bin/pg_upgrade/tmp_check/results/join.out
--- /tmp/cirrus-ci-build/src/test/regress/expected/join.out	2025-01-31 05:03:32.924467657 +0000
+++ /tmp/cirrus-ci-build/src/bin/pg_upgrade/tmp_check/results/join.out	2025-01-31 05:11:23.613900541 +0000
@@ -5969,6 +5969,8 @@
          ->  Seq Scan on c
 (7 rows)
 
+-- check the case when placeholder relates on an outer join and its inner in the
+-- phrels field but actually uses only outer side of the join.
 explain (costs off)
 SELECT q.val FROM b LEFT JOIN (
   SELECT (q1.z IS NOT NULL) AS val