Fix crash with ORCA for partition tables with rewritten rules

Earlier, the check for identifying if a table is randomly distributed relied
on the policy to be not null, however if we have rewritten rules on child
partition table, the table storage is marked as RELSTORAGE_VIRTUAL which can
lead to null policy.

Should the table be marked with virtual storage, that's a different issue though.

src/backend/utils/cache/lsyscache.c

@@ -4084,7 +4084,7 @@ child_distribution_mismatch(Relation rel)
 	GpPolicy *rootPolicy = rel->rd_cdbpolicy;
 	Assert(NULL != rootPolicy && "Partitioned tables cannot be master-only");
 
-	if (POLICYTYPE_PARTITIONED == rootPolicy->ptype && 0 == rootPolicy->nattrs)
+	if (GpPolicyIsRandomly(rootPolicy))
 	{
 		/* root partition policy already marked as Random, no mismatch possible as
 		 * all children must be random as well */
@@ -4101,7 +4101,8 @@ child_distribution_mismatch(Relation rel)
 		Assert(NULL != relChild);
 
 		GpPolicy *childPolicy = relChild->rd_cdbpolicy;
-		if (POLICYTYPE_PARTITIONED == childPolicy->ptype && 0 == childPolicy->nattrs)
+
+		if (GpPolicyIsRandomly(childPolicy))
 		{
 			/* child partition is Random, and parent is not */
 			RelationClose(relChild);

src/test/regress/expected/gporca.out

@@ -10588,3 +10588,17 @@ WITH abc AS (SELECT onetimefilter1.a, onetimefilter1.b FROM onetimefilter1, onet
         1 |        0 |        2
 (10 rows)
 
+-- queries on partition table with rewritten rule should not crash
+-- github issue #5913
+create table rewrite_rules (id int, stamp date, amount int)
+with (appendonly=false) distributed by (id)
+partition by range (stamp) (
+  start ('2018-01-01') end ('2019-01-01') every(interval '1 year'),
+  default partition extra
+);
+NOTICE:  CREATE TABLE will create partition "rewrite_rules_1_prt_extra" for table "rewrite_rules"
+NOTICE:  CREATE TABLE will create partition "rewrite_rules_1_prt_2" for table "rewrite_rules"
+create rule "_RETURN" as on select to rewrite_rules_1_prt_2 do instead 
+select 1 as id, current_date as stamp, 1 as amount;
+select * from rewrite_rules;
+ERROR:  plan contains range table with relstorage='v' (allpaths.c:346)

src/test/regress/expected/gporca_optimizer.out

@@ -10655,3 +10655,17 @@ WITH abc AS (SELECT onetimefilter1.a, onetimefilter1.b FROM onetimefilter1, onet
         1 |        0 |        2
 (10 rows)
 
+-- queries on partition table with rewritten rule should not crash
+-- github issue #5913
+create table rewrite_rules (id int, stamp date, amount int)
+with (appendonly=false) distributed by (id)
+partition by range (stamp) (
+  start ('2018-01-01') end ('2019-01-01') every(interval '1 year'),
+  default partition extra
+);
+NOTICE:  CREATE TABLE will create partition "rewrite_rules_1_prt_extra" for table "rewrite_rules"
+NOTICE:  CREATE TABLE will create partition "rewrite_rules_1_prt_2" for table "rewrite_rules"
+create rule "_RETURN" as on select to rewrite_rules_1_prt_2 do instead 
+select 1 as id, current_date as stamp, 1 as amount;
+select * from rewrite_rules;
+ERROR:  undefined table type for storage format: v (execScan.c:414)

src/test/regress/sql/gporca.sql

@@ -1623,6 +1623,18 @@ ANALYZE onetimefilter2;
 EXPLAIN WITH abc AS (SELECT onetimefilter1.a, onetimefilter1.b FROM onetimefilter1, onetimefilter2 WHERE onetimefilter1.a=onetimefilter2.a) SELECT (SELECT 1 FROM abc WHERE f1.b = f2.b LIMIT 1), COALESCE((SELECT 2 FROM abc WHERE f1.a=random() AND f1.a=2), 0), (SELECT b FROM abc WHERE b=f1.b) FROM onetimefilter1 f1, onetimefilter2 f2 WHERE f1.b = f2.b;
 WITH abc AS (SELECT onetimefilter1.a, onetimefilter1.b FROM onetimefilter1, onetimefilter2 WHERE onetimefilter1.a=onetimefilter2.a) SELECT (SELECT 1 FROM abc WHERE f1.b = f2.b LIMIT 1), COALESCE((SELECT 2 FROM abc WHERE f1.a=random() AND f1.a=2), 0), (SELECT b FROM abc WHERE b=f1.b) FROM onetimefilter1 f1, onetimefilter2 f2 WHERE f1.b = f2.b;
 
+-- queries on partition table with rewritten rule should not crash
+-- github issue #5913
+create table rewrite_rules (id int, stamp date, amount int)
+with (appendonly=false) distributed by (id)
+partition by range (stamp) (
+  start ('2018-01-01') end ('2019-01-01') every(interval '1 year'),
+  default partition extra
+);
+create rule "_RETURN" as on select to rewrite_rules_1_prt_2 do instead 
+select 1 as id, current_date as stamp, 1 as amount;
+select * from rewrite_rules;
+
 -- start_ignore
 DROP SCHEMA orca CASCADE;
 -- end_ignore