Support CREATE INDEX ONLY ON main table

This PR adds support for CREATE INDEX ONLY ON clause which allows to
create index only on the main table excluding chunks.

Fix #5908

.unreleased/bugfix_5909

@@ -0,0 +1 @@
+Implements: #5909 CREATE INDEX ONLY ON hypertable creates index on chunks

src/process_utility.c

@@ -2791,6 +2791,7 @@ process_index_start(ProcessUtilityArgs *args)
 		ts_cagg_permissions_check(ht->main_table_relid, GetUserId());
 		SWITCH_TO_TS_USER(NameStr(cagg->data.direct_view_schema), uid, saved_uid, sec_ctx);
 	}
+
 	/* CREATE INDEX on the root table of the hypertable */
 	root_table_index = ts_indexing_root_table_create_index(stmt,
 														   args->query_string,
@@ -2799,6 +2800,7 @@ process_index_start(ProcessUtilityArgs *args)
 
 	if (cagg)
 		RESTORE_USER(uid, saved_uid, sec_ctx);
+
 	/* root_table_index will have 0 objectId if the index already exists
 	 * and if_not_exists is true. In that case there is nothing else
 	 * to do here. */
@@ -2808,7 +2810,13 @@ process_index_start(ProcessUtilityArgs *args)
 		return DDL_DONE;
 	}
 	Assert(OidIsValid(root_table_index.objectId));
-	info.obj.objectId = root_table_index.objectId;
+
+	/* support ONLY ON clause, index on root table already created */
+	if (!stmt->relation->inh)
+	{
+		ts_cache_release(hcache);
+		return DDL_DONE;
+	}
 
 	/* CREATE INDEX on the chunks, unless this is a distributed hypertable */
 	if (hypertable_is_distributed(ht))
@@ -2817,6 +2825,7 @@ process_index_start(ProcessUtilityArgs *args)
 		return DDL_DONE;
 	}
 
+	info.obj.objectId = root_table_index.objectId;
 	/* collect information required for per chunk index creation */
 	main_table_relation = table_open(ht->main_table_relid, AccessShareLock);
 	main_table_desc = RelationGetDescr(main_table_relation);

test/expected/index.out

@@ -726,3 +726,58 @@ SELECT table_name FROM create_hypertable('i3056', 'date_created');
 
 ALTER TABLE i3056 DROP COLUMN c;
 INSERT INTO i3056(order_number,date_created) VALUES (1, '2000-01-01');
+-- #5908 test CREATE INDEX ON ONLY main table
+CREATE TABLE test(time timestamptz, temp float);
+SELECT create_hypertable('test', 'time');
+NOTICE:  adding not-null constraint to column "time"
+ create_hypertable  
+--------------------
+ (15,public,test,t)
+(1 row)
+
+INSERT INTO test (time,temp) VALUES
+       (generate_series(TIMESTAMP '2019-08-01', TIMESTAMP '2019-08-10', INTERVAL '10 minutes'), ROUND(RANDOM()*10)::float);
+SELECT * FROM show_chunks('test');
+               show_chunks                
+------------------------------------------
+ _timescaledb_internal._hyper_15_21_chunk
+ _timescaledb_internal._hyper_15_22_chunk
+(2 rows)
+
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');
+                         Index                          | Columns | Expr | Unique | Primary | Exclusion | Tablespace 
+--------------------------------------------------------+---------+------+--------+---------+-----------+------------
+ _timescaledb_internal._hyper_15_21_chunk_test_time_idx | {time}  |      | f      | f       | f         | 
+(1 row)
+
+-- create index per chunk
+CREATE INDEX _hyper_15_21_chunk_test_temp_idx ON  _timescaledb_internal._hyper_15_21_chunk(temp);
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');
+                         Index                          | Columns | Expr | Unique | Primary | Exclusion | Tablespace 
+--------------------------------------------------------+---------+------+--------+---------+-----------+------------
+ _timescaledb_internal._hyper_15_21_chunk_test_temp_idx | {temp}  |      | f      | f       | f         | 
+ _timescaledb_internal._hyper_15_21_chunk_test_time_idx | {time}  |      | f      | f       | f         | 
+(2 rows)
+
+SELECT * FROM test.show_indexes('test');
+     Index     | Columns | Expr | Unique | Primary | Exclusion | Tablespace 
+---------------+---------+------+--------+---------+-----------+------------
+ test_time_idx | {time}  |      | f      | f       | f         | 
+(1 row)
+
+-- create index only on main table
+CREATE INDEX test_temp_idx ON ONLY test (time);
+SELECT * FROM test.show_indexes('test');
+     Index     | Columns | Expr | Unique | Primary | Exclusion | Tablespace 
+---------------+---------+------+--------+---------+-----------+------------
+ test_temp_idx | {time}  |      | f      | f       | f         | 
+ test_time_idx | {time}  |      | f      | f       | f         | 
+(2 rows)
+
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');
+                         Index                          | Columns | Expr | Unique | Primary | Exclusion | Tablespace 
+--------------------------------------------------------+---------+------+--------+---------+-----------+------------
+ _timescaledb_internal._hyper_15_21_chunk_test_temp_idx | {temp}  |      | f      | f       | f         | 
+ _timescaledb_internal._hyper_15_21_chunk_test_time_idx | {time}  |      | f      | f       | f         | 
+(2 rows)
+

test/sql/index.sql

@@ -342,4 +342,22 @@ SELECT table_name FROM create_hypertable('i3056', 'date_created');
 ALTER TABLE i3056 DROP COLUMN c;
 INSERT INTO i3056(order_number,date_created) VALUES (1, '2000-01-01');
 
+-- #5908 test CREATE INDEX ON ONLY main table
+CREATE TABLE test(time timestamptz, temp float);
+SELECT create_hypertable('test', 'time');
 
+INSERT INTO test (time,temp) VALUES
+       (generate_series(TIMESTAMP '2019-08-01', TIMESTAMP '2019-08-10', INTERVAL '10 minutes'), ROUND(RANDOM()*10)::float);
+SELECT * FROM show_chunks('test');
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');
+
+-- create index per chunk
+CREATE INDEX _hyper_15_21_chunk_test_temp_idx ON  _timescaledb_internal._hyper_15_21_chunk(temp);
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');
+SELECT * FROM test.show_indexes('test');
+
+-- create index only on main table
+CREATE INDEX test_temp_idx ON ONLY test (time);
+
+SELECT * FROM test.show_indexes('test');
+SELECT * FROM test.show_indexes('_timescaledb_internal._hyper_15_21_chunk');