Give nicer error message when using alter_table_set_access_method on a view (#6553)

DESCRIPTION: Fixes alter_table_set_access_method error for views.

Fixes #6001

src/backend/distributed/commands/alter_table.c

@@ -477,6 +477,11 @@ AlterTableSetAccessMethod(TableConversionParameters *params)
 		ereport(ERROR, (errmsg("you cannot alter access method of a partitioned table")));
 	}
 
+	if (get_rel_relkind(params->relationId) == RELKIND_VIEW)
+	{
+		ereport(ERROR, (errmsg("you cannot alter access method of a view")));
+	}
+
 	if (PartitionTable(params->relationId) &&
 		IsCitusTableType(params->relationId, DISTRIBUTED_TABLE))
 	{

src/test/regress/expected/alter_table_set_access_method.out

@@ -299,7 +299,7 @@ CREATE INDEX idx1 ON index_table (a);
 -- also create an index with statistics
 CREATE INDEX idx2 ON index_table ((a+1));
 ALTER INDEX idx2 ALTER COLUMN 1 SET STATISTICS 300;
-SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table';
+SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table' order by indexname;
  indexname
 ---------------------------------------------------------------------
  idx1
@@ -322,7 +322,7 @@ NOTICE:  renaming the new table to alter_table_set_access_method.index_table
 
 (1 row)
 
-SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table';
+SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table' order by indexname;
  indexname
 ---------------------------------------------------------------------
  idx1
@@ -792,6 +792,19 @@ NOTICE:  renaming the new table to alter_table_set_access_method.events
 (1 row)
 
 COMMIT;
+--create the view to test alter table set access method on it
+CREATE TABLE view_test_table (id int, val int, flag bool, kind int);
+SELECT create_distributed_table('view_test_table','id');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO view_test_table VALUES (1, 1, true, 99), (2, 2, false, 99), (2, 3, true, 88);
+CREATE VIEW view_test_view AS SELECT * FROM view_test_table;
+-- error out when attempting to set access method of a view.
+select alter_table_set_access_method('view_test_view','columnar');
+ERROR:  you cannot alter access method of a view
 SET client_min_messages TO WARNING;
 DROP SCHEMA alter_table_set_access_method CASCADE;
 SELECT 1 FROM master_remove_node('localhost', :master_port);

src/test/regress/sql/alter_table_set_access_method.sql

@@ -99,10 +99,10 @@ CREATE INDEX idx1 ON index_table (a);
 -- also create an index with statistics
 CREATE INDEX idx2 ON index_table ((a+1));
 ALTER INDEX idx2 ALTER COLUMN 1 SET STATISTICS 300;
-SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table';
+SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table' order by indexname;
 SELECT a.amname FROM pg_class c, pg_am a where c.relname = 'index_table' AND c.relnamespace = 'alter_table_set_access_method'::regnamespace AND c.relam = a.oid;
 SELECT alter_table_set_access_method('index_table', 'columnar');
-SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table';
+SELECT indexname FROM pg_indexes WHERE schemaname = 'alter_table_set_access_method' AND tablename = 'index_table' order by indexname;
 SELECT a.amname FROM pg_class c, pg_am a where c.relname = 'index_table' AND c.relnamespace = 'alter_table_set_access_method'::regnamespace AND c.relam = a.oid;
 
 CREATE TABLE "heap_\'tbl" (
@@ -271,6 +271,15 @@ BEGIN;
   select alter_table_set_access_method('events', 'columnar');
 COMMIT;
 
+--create the view to test alter table set access method on it
+CREATE TABLE view_test_table (id int, val int, flag bool, kind int);
+SELECT create_distributed_table('view_test_table','id');
+INSERT INTO view_test_table VALUES (1, 1, true, 99), (2, 2, false, 99), (2, 3, true, 88);
+CREATE VIEW view_test_view AS SELECT * FROM view_test_table;
+
+-- error out when attempting to set access method of a view.
+select alter_table_set_access_method('view_test_view','columnar');
+
 SET client_min_messages TO WARNING;
 DROP SCHEMA alter_table_set_access_method CASCADE;
 SELECT 1 FROM master_remove_node('localhost', :master_port);