check query plan during physical planning for outer joins

src/backend/distributed/planner/multi_physical_planner.c

@@ -2302,6 +2302,18 @@ QueryPushdownSqlTaskList(Query *query, uint64 jobId,
 		}
 	}
 
+	/*
+	 * We might fail to find outer joins from the relationRestrictionContext
+	 * when the original query has CTEs. In order to ensure that we always mark
+	 * the outer joins correctly and compute additional quals when necessary,
+	 * check the task query as well.
+	 */
+	if (!updateQualsForOuterJoin && FindNodeMatchingCheckFunction((Node *) query,
+																  IsOuterJoinExpr))
+	{
+		updateQualsForOuterJoin = true;
+	}
+
 	/*
 	 * We keep track of minShardOffset to skip over a potentially big amount of pruned
 	 * shards. However, we need to start at minShardOffset - 1 to make sure we don't

src/test/regress/expected/recurring_join_pushdown.out

@@ -845,6 +845,14 @@ DEBUG:  assigned task to node localhost:xxxxx
 (1 row)
 
 SET client_min_messages TO ERROR;
+-- Ensure that even when CTEs are replaced, we insert push
+-- down conditions for outer joins when necessary.
+WITH  cte_0 AS ( SELECT table_0.a FROM d1 AS table_0 WHERE table_0.a IN ( SELECT table_1.a FROM d1 AS table_1 ORDER BY a LIMIT 2 )  ORDER BY a ) SELECT count(*), avg(avgsub.a) FROM ( SELECT table_2.a FROM cte_0 AS table_2 RIGHT JOIN r1 AS table_3 USING (a)) AS avgsub;
+ count |          avg
+---------------------------------------------------------------------
+    15 | 1.00000000000000000000
+(1 row)
+
 -- The following queries trigger recursive computing, recurring outer-join push down
 -- methods introduced in#7973 can be enhanced to cover these cases in the future.
 CREATE TABLE r1_local AS SELECT * FROM r1;

src/test/regress/sql/recurring_join_pushdown.sql

@@ -117,6 +117,11 @@ SELECT count(*) FROM (SELECT * FROM d1) AS t1 RIGHT JOIN r1 USING (a);
 
 SET client_min_messages TO ERROR;
 
+-- Ensure that even when CTEs are replaced, we insert push
+-- down conditions for outer joins when necessary.
+WITH  cte_0 AS ( SELECT table_0.a FROM d1 AS table_0 WHERE table_0.a IN ( SELECT table_1.a FROM d1 AS table_1 ORDER BY a LIMIT 2 )  ORDER BY a ) SELECT count(*), avg(avgsub.a) FROM ( SELECT table_2.a FROM cte_0 AS table_2 RIGHT JOIN r1 AS table_3 USING (a)) AS avgsub;
+
+
 -- The following queries trigger recursive computing, recurring outer-join push down
 -- methods introduced in#7973 can be enhanced to cover these cases in the future.
 CREATE TABLE r1_local AS SELECT * FROM r1;