Fix possible crash in partition-wise join.

The previous code assumed that we'd always succeed in creating
child-joins for a joinrel for which partition-wise join was considered,
but that's not guaranteed, at least in the case where dummy rels
are involved.

Ashutosh Bapat, with some wordsmithing by me.

Discussion: http://postgr.es/m/CAFjFpRf8=uyMYYfeTBjWDMs1tR5t--FgOe2vKZPULxxdYQ4RNw@mail.gmail.com

2 files changed, 26 insertions, 19 deletions

diff --git a/src/test/regress/expected/partition_join.out b/src/test/regress/expected/partition_join.out
index 27ab8521f84..333f93889cf 100644
--- a/src/test/regress/expected/partition_join.out
+++ b/src/test/regress/expected/partition_join.out
@@ -1217,24 +1217,31 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1
 (2 rows)
 
 EXPLAIN (COSTS OFF)
-SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 RIGHT JOIN prt2 t2 ON t1.a = t2.b WHERE t2.a = 0 ORDER BY t1.a, t2.b;
-                 QUERY PLAN                 
---------------------------------------------
- Sort
-   Sort Key: a, t2.b
-   ->  Hash Left Join
-         Hash Cond: (t2.b = a)
-         ->  Append
-               ->  Seq Scan on prt2_p1 t2
-                     Filter: (a = 0)
-               ->  Seq Scan on prt2_p2 t2_1
-                     Filter: (a = 0)
-               ->  Seq Scan on prt2_p3 t2_2
-                     Filter: (a = 0)
-         ->  Hash
-               ->  Result
-                     One-Time Filter: false
-(14 rows)
+SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 RIGHT JOIN prt2 t2 ON t1.a = t2.b, prt1 t3 WHERE t2.b = t3.a;
+                    QUERY PLAN                    
+--------------------------------------------------
+ Hash Left Join
+   Hash Cond: (t2.b = a)
+   ->  Append
+         ->  Hash Join
+               Hash Cond: (t3.a = t2.b)
+               ->  Seq Scan on prt1_p1 t3
+               ->  Hash
+                     ->  Seq Scan on prt2_p1 t2
+         ->  Hash Join
+               Hash Cond: (t3_1.a = t2_1.b)
+               ->  Seq Scan on prt1_p2 t3_1
+               ->  Hash
+                     ->  Seq Scan on prt2_p2 t2_1
+         ->  Hash Join
+               Hash Cond: (t3_2.a = t2_2.b)
+               ->  Seq Scan on prt1_p3 t3_2
+               ->  Hash
+                     ->  Seq Scan on prt2_p3 t2_2
+   ->  Hash
+         ->  Result
+               One-Time Filter: false
+(21 rows)
 
 EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 FULL JOIN prt2 t2 ON t1.a = t2.b WHERE t2.a = 0 ORDER BY t1.a, t2.b;
diff --git a/src/test/regress/sql/partition_join.sql b/src/test/regress/sql/partition_join.sql
index 6efdf3c5175..55c5615d06c 100644
--- a/src/test/regress/sql/partition_join.sql
+++ b/src/test/regress/sql/partition_join.sql
@@ -224,7 +224,7 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 LEFT JOIN prt2 t2 ON t1.a = t2.b;
 
 EXPLAIN (COSTS OFF)
-SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 RIGHT JOIN prt2 t2 ON t1.a = t2.b WHERE t2.a = 0 ORDER BY t1.a, t2.b;
+SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 RIGHT JOIN prt2 t2 ON t1.a = t2.b, prt1 t3 WHERE t2.b = t3.a;
 
 EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM (SELECT * FROM prt1 WHERE a = 1 AND a = 2) t1 FULL JOIN prt2 t2 ON t1.a = t2.b WHERE t2.a = 0 ORDER BY t1.a, t2.b;