Add support for SET ACCESS METHOD in altering a distributed table (#6525)

Co-authored-by: TsinghuaLucky912 <postgres@localhost.localdomain>

src/backend/distributed/commands/table.c

@@ -2992,6 +2992,9 @@ ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement)
 				break;
 			}
 
+#if PG_VERSION_NUM >= PG_VERSION_15
+			case AT_SetAccessMethod:
+#endif
 			case AT_SetNotNull:
 			case AT_ReplicaIdentity:
 			case AT_ChangeOwner:
@@ -3007,6 +3010,7 @@ ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement)
 				{
 					/*
 					 * We will not perform any special check for:
+					 * ALTER TABLE .. SET ACCESS METHOD ..
 					 * ALTER TABLE .. ALTER COLUMN .. SET NOT NULL
 					 * ALTER TABLE .. REPLICA IDENTITY ..
 					 * ALTER TABLE .. VALIDATE CONSTRAINT ..

src/test/regress/expected/pg15.out

@@ -1456,6 +1456,36 @@ NOTICE:  drop cascades to 2 other objects
 CREATE DATABASE db_with_oid OID 987654;
 NOTICE:  Citus partially supports CREATE DATABASE for distributed databases
 DROP DATABASE db_with_oid;
+-- SET ACCESS METHOD
+-- Create a heap2 table am handler with heapam handler
+CREATE ACCESS METHOD heap2 TYPE TABLE HANDLER heap_tableam_handler;
+SELECT run_command_on_workers($$CREATE ACCESS METHOD heap2 TYPE TABLE HANDLER heap_tableam_handler$$);
+           run_command_on_workers
+---------------------------------------------------------------------
+ (localhost,57637,t,"CREATE ACCESS METHOD")
+ (localhost,57638,t,"CREATE ACCESS METHOD")
+(2 rows)
+
+CREATE TABLE mx_ddl_table2 (
+    key int primary key,
+    value int
+);
+SELECT create_distributed_table('mx_ddl_table2', 'key', 'hash', shard_count=> 4);
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+ALTER TABLE mx_ddl_table2 SET ACCESS METHOD heap2;
+DROP TABLE mx_ddl_table2;
+DROP ACCESS METHOD heap2;
+SELECT run_command_on_workers($$DROP ACCESS METHOD heap2$$);
+          run_command_on_workers
+---------------------------------------------------------------------
+ (localhost,57637,t,"DROP ACCESS METHOD")
+ (localhost,57638,t,"DROP ACCESS METHOD")
+(2 rows)
+
 -- Clean up
 \set VERBOSITY terse
 SET client_min_messages TO ERROR;

src/test/regress/sql/pg15.sql

@@ -924,6 +924,21 @@ DROP SERVER foreign_server CASCADE;
 CREATE DATABASE db_with_oid OID 987654;
 DROP DATABASE db_with_oid;
 
+-- SET ACCESS METHOD
+-- Create a heap2 table am handler with heapam handler
+CREATE ACCESS METHOD heap2 TYPE TABLE HANDLER heap_tableam_handler;
+SELECT run_command_on_workers($$CREATE ACCESS METHOD heap2 TYPE TABLE HANDLER heap_tableam_handler$$);
+CREATE TABLE mx_ddl_table2 (
+    key int primary key,
+    value int
+);
+SELECT create_distributed_table('mx_ddl_table2', 'key', 'hash', shard_count=> 4);
+ALTER TABLE mx_ddl_table2 SET ACCESS METHOD heap2;
+
+DROP TABLE mx_ddl_table2;
+DROP ACCESS METHOD heap2;
+SELECT run_command_on_workers($$DROP ACCESS METHOD heap2$$);
+
 -- Clean up
 \set VERBOSITY terse
 SET client_min_messages TO ERROR;