Inherit parent's AM for partition MERGE/SPLIT operations

This commit makes new partitions created by ALTER TABLE ... SPLIT PARTITION
and ALTER TABLE ... MERGE PARTITIONS commands inherit the paret table access
method.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/84ada05b-be5c-473e-6d1c-ebe5dd21b190%40gmail.com
Reviewed-by: Pavel Borisov

src/backend/commands/tablecmds.c

@@ -21213,6 +21213,11 @@ moveSplitTableRows(Relation rel, Relation splitRel, List *partlist, List *newPar
  *
  * Emulates command: CREATE [TEMP] TABLE <newPartName> (LIKE <modelRel's name>
  * INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY)
+ *
+ * Also, this function sets the new partition access method same as parent
+ * table access methods (similarly to CREATE TABLE ... PARTITION OF).  It
+ * checks that parent and child tables have compatible persistence.
+ *
  * Function returns the created relation (locked in AccessExclusiveLock mode).
  */
 static Relation
@@ -21243,6 +21248,7 @@ createPartitionTable(RangeVar *newPartName, Relation modelRel,
 	createStmt->oncommit = ONCOMMIT_NOOP;
 	createStmt->tablespacename = NULL;
 	createStmt->if_not_exists = false;
+	createStmt->accessMethod = get_am_name(modelRel->rd_rel->relam);
 
 	tlc = makeNode(TableLikeClause);
 	tlc->relation = makeRangeVar(get_namespace_name(RelationGetNamespace(modelRel)),

src/test/regress/expected/partition_merge.out

@@ -862,6 +862,24 @@ SET search_path = partitions_merge_schema, pg_temp, public;
 -- Can't merge temporary partitions into a persistent partition
 ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
 ROLLBACK;
+-- Check the new partition inherits parent's table access method
+SET search_path = partitions_merge_schema, public;
+CREATE ACCESS METHOD partitions_merge_heap TYPE TABLE HANDLER heap_tableam_handler;
+CREATE TABLE t (i int) PARTITION BY RANGE (i) USING partitions_merge_heap;
+CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (0) TO (1);
+CREATE TABLE tp_1_2 PARTITION OF t FOR VALUES FROM (1) TO (2);
+ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
+SELECT c.relname, a.amname
+FROM pg_class c JOIN pg_am a ON c.relam = a.oid
+WHERE c.oid IN ('t'::regclass, 'tp_0_2'::regclass);
+ relname |        amname         
+---------+-----------------------
+ tp_0_2  | partitions_merge_heap
+ t       | partitions_merge_heap
+(2 rows)
+
+DROP TABLE t;
+DROP ACCESS METHOD partitions_merge_heap;
 RESET search_path;
 --
 DROP SCHEMA partitions_merge_schema;

src/test/regress/expected/partition_split.out

@@ -85,8 +85,8 @@ ALTER TABLE sales_range SPLIT PARTITION sales_feb_mar_apr2022 INTO
    PARTITION sales_mar2022 FOR VALUES FROM ('2022-03-01') TO ('2022-04-01'),
    PARTITION sales_apr2022 FOR VALUES FROM ('2022-04-01') TO ('2022-06-01'));
 ERROR:  upper bound of partition "sales_apr2022" is greater than upper bound of split partition
-LINE 4:    PARTITION sales_apr2022 FOR VALUES FROM ('2022-04-01') TO...
-                                                    ^
+LINE 4: ... sales_apr2022 FOR VALUES FROM ('2022-04-01') TO ('2022-06-0...
+                                                             ^
 -- ERROR:  lower bound of partition "sales_mar2022" conflicts with upper bound of previous partition "sales_feb2022"
 ALTER TABLE sales_range SPLIT PARTITION sales_feb_mar_apr2022 INTO
   (PARTITION sales_feb2022 FOR VALUES FROM ('2022-02-01') TO ('2022-03-01'),
@@ -1494,6 +1494,25 @@ SELECT c.oid::pg_catalog.regclass, pg_catalog.pg_get_expr(c.relpartbound, c.oid)
 (2 rows)
 
 DROP TABLE t;
+-- Check new partitions inherits parent's table access method
+CREATE ACCESS METHOD partition_split_heap TYPE TABLE HANDLER heap_tableam_handler;
+CREATE TABLE t (i int) PARTITION BY RANGE (i) USING partition_split_heap;
+CREATE TABLE tp_0_2 PARTITION OF t FOR VALUES FROM (0) TO (2);
+ALTER TABLE t SPLIT PARTITION tp_0_2 INTO
+  (PARTITION tp_0_1 FOR VALUES FROM (0) TO (1),
+   PARTITION tp_1_2 FOR VALUES FROM (1) TO (2));
+SELECT c.relname, a.amname
+FROM pg_class c JOIN pg_am a ON c.relam = a.oid
+WHERE c.oid IN ('t'::regclass, 'tp_0_1'::regclass, 'tp_1_2'::regclass);
+ relname |        amname        
+---------+----------------------
+ t       | partition_split_heap
+ tp_0_1  | partition_split_heap
+ tp_1_2  | partition_split_heap
+(3 rows)
+
+DROP TABLE t;
+DROP ACCESS METHOD partition_split_heap;
 --
 DROP SCHEMA partition_split_schema;
 DROP SCHEMA partition_split_schema2;

src/test/regress/sql/partition_merge.sql

@@ -535,6 +535,19 @@ SET search_path = partitions_merge_schema, pg_temp, public;
 ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
 ROLLBACK;
 
+-- Check the new partition inherits parent's table access method
+SET search_path = partitions_merge_schema, public;
+CREATE ACCESS METHOD partitions_merge_heap TYPE TABLE HANDLER heap_tableam_handler;
+CREATE TABLE t (i int) PARTITION BY RANGE (i) USING partitions_merge_heap;
+CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (0) TO (1);
+CREATE TABLE tp_1_2 PARTITION OF t FOR VALUES FROM (1) TO (2);
+ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
+SELECT c.relname, a.amname
+FROM pg_class c JOIN pg_am a ON c.relam = a.oid
+WHERE c.oid IN ('t'::regclass, 'tp_0_2'::regclass);
+DROP TABLE t;
+DROP ACCESS METHOD partitions_merge_heap;
+
 RESET search_path;
 
 --

src/test/regress/sql/partition_split.sql

@@ -880,6 +880,20 @@ SELECT c.oid::pg_catalog.regclass, pg_catalog.pg_get_expr(c.relpartbound, c.oid)
 
 DROP TABLE t;
 
+-- Check new partitions inherits parent's table access method
+CREATE ACCESS METHOD partition_split_heap TYPE TABLE HANDLER heap_tableam_handler;
+CREATE TABLE t (i int) PARTITION BY RANGE (i) USING partition_split_heap;
+CREATE TABLE tp_0_2 PARTITION OF t FOR VALUES FROM (0) TO (2);
+ALTER TABLE t SPLIT PARTITION tp_0_2 INTO
+  (PARTITION tp_0_1 FOR VALUES FROM (0) TO (1),
+   PARTITION tp_1_2 FOR VALUES FROM (1) TO (2));
+SELECT c.relname, a.amname
+FROM pg_class c JOIN pg_am a ON c.relam = a.oid
+WHERE c.oid IN ('t'::regclass, 'tp_0_1'::regclass, 'tp_1_2'::regclass);
+DROP TABLE t;
+DROP ACCESS METHOD partition_split_heap;
+
+
 --
 DROP SCHEMA partition_split_schema;
 DROP SCHEMA partition_split_schema2;