Disable MERGE when using hypertables

Fixes timescale#4930

Co-authored-by: Lakshmi Narayanan Sreethar <lakshmi@timescale.com>

src/planner/planner.c

@@ -1423,6 +1423,14 @@ replace_hypertable_modify_paths(PlannerInfo *root, List *pathlist, RelOptInfo *i
 		if (IsA(path, ModifyTablePath))
 		{
 			ModifyTablePath *mt = castNode(ModifyTablePath, path);
+#if PG15_GE
+			if (mt->operation == CMD_MERGE)
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("The MERGE command does not support hypertables in this version"),
+						 errhint("Check https://github.com/timescale/timescaledb/issues/4929 for"
+								 "more information and current status")));
+#endif
 
 #if PG14_GE
 			/* We only route UPDATE/DELETE through our CustomNode for PG 14+ because

test/expected/merge.out

@@ -0,0 +1,137 @@
+-- This file and its contents are licensed under the Apache License 2.0.
+-- Please see the included NOTICE for copyright information and
+-- LICENSE-APACHE for a copy of the license.
+-- Create conditions table with location and temperature
+DROP TABLE IF EXISTS conditions;
+NOTICE:  table "conditions" does not exist, skipping
+CREATE TABLE conditions (
+   time        TIMESTAMPTZ       NOT NULL,
+   location    SMALLINT          NOT NULL,
+   temperature DOUBLE PRECISION  NULL
+);
+SELECT create_hypertable(
+  'conditions',
+  'time',
+  chunk_time_interval => INTERVAL '5 seconds');
+    create_hypertable    
+-------------------------
+ (1,public,conditions,t)
+(1 row)
+
+
+INSERT INTO conditions
+SELECT time, location, 14 as temperature
+FROM generate_series(
+	'2021-01-01 00:00:00',
+    '2021-01-01 00:00:09',
+    INTERVAL '5 seconds'
+  ) as time,
+generate_series(1,4) as location;
+-- Create conditions_updated table with location and temperature
+DROP TABLE IF EXISTS conditions_updated;
+NOTICE:  table "conditions_updated" does not exist, skipping
+CREATE TABLE conditions_updated (
+   time        TIMESTAMPTZ       NOT NULL,
+   location    SMALLINT          NOT NULL,
+   temperature DOUBLE PRECISION  NULL
+);
+SELECT create_hypertable(
+  'conditions_updated',
+  'time',
+  chunk_time_interval => INTERVAL '5 seconds');
+        create_hypertable        
+---------------------------------
+ (2,public,conditions_updated,t)
+(1 row)
+
+-- Generate data that overlaps with conditions table
+INSERT INTO conditions_updated
+SELECT time, location, 80 as temperature
+FROM generate_series(
+	'2021-01-01 00:00:05',
+    '2021-01-01 00:00:14',
+    INTERVAL '5 seconds'
+  ) as time,
+generate_series(1,4) as location;
+-- Print table/rows/num of chunks
+select * from conditions order by time, location asc;
+             time             | location | temperature 
+------------------------------+----------+-------------
+ Fri Jan 01 00:00:00 2021 PST |        1 |          14
+ Fri Jan 01 00:00:00 2021 PST |        2 |          14
+ Fri Jan 01 00:00:00 2021 PST |        3 |          14
+ Fri Jan 01 00:00:00 2021 PST |        4 |          14
+ Fri Jan 01 00:00:05 2021 PST |        1 |          14
+ Fri Jan 01 00:00:05 2021 PST |        2 |          14
+ Fri Jan 01 00:00:05 2021 PST |        3 |          14
+ Fri Jan 01 00:00:05 2021 PST |        4 |          14
+(8 rows)
+
+select * from conditions_updated order by time, location asc;
+             time             | location | temperature 
+------------------------------+----------+-------------
+ Fri Jan 01 00:00:05 2021 PST |        1 |          80
+ Fri Jan 01 00:00:05 2021 PST |        2 |          80
+ Fri Jan 01 00:00:05 2021 PST |        3 |          80
+ Fri Jan 01 00:00:05 2021 PST |        4 |          80
+ Fri Jan 01 00:00:10 2021 PST |        1 |          80
+ Fri Jan 01 00:00:10 2021 PST |        2 |          80
+ Fri Jan 01 00:00:10 2021 PST |        3 |          80
+ Fri Jan 01 00:00:10 2021 PST |        4 |          80
+(8 rows)
+
+select hypertable_name, count(*) as num_of_chunks from timescaledb_information.chunks group by hypertable_name;
+  hypertable_name   | num_of_chunks 
+--------------------+---------------
+ conditions         |             2
+ conditions_updated |             2
+(2 rows)
+
+-- Print expected values in the conditions table once conditions_updated is merged into it
+-- If a key exists in both tables, we take average of the temperature measured
+-- average logic here is a mess but it works
+SELECT COALESCE(c.time, cu.time) as time,
+       COALESCE(c.location, cu.location) as location,
+       (COALESCE(c.temperature, cu.temperature) + COALESCE(cu.temperature, c.temperature))/2 as temperature 
+FROM conditions AS c FULL JOIN conditions_updated AS cu
+ON c.time = cu.time AND c.location = cu.location;
+             time             | location | temperature 
+------------------------------+----------+-------------
+ Fri Jan 01 00:00:00 2021 PST |        1 |          14
+ Fri Jan 01 00:00:00 2021 PST |        2 |          14
+ Fri Jan 01 00:00:00 2021 PST |        3 |          14
+ Fri Jan 01 00:00:00 2021 PST |        4 |          14
+ Fri Jan 01 00:00:05 2021 PST |        1 |          47
+ Fri Jan 01 00:00:05 2021 PST |        2 |          47
+ Fri Jan 01 00:00:05 2021 PST |        3 |          47
+ Fri Jan 01 00:00:05 2021 PST |        4 |          47
+ Fri Jan 01 00:00:10 2021 PST |        1 |          80
+ Fri Jan 01 00:00:10 2021 PST |        2 |          80
+ Fri Jan 01 00:00:10 2021 PST |        3 |          80
+ Fri Jan 01 00:00:10 2021 PST |        4 |          80
+(12 rows)
+
+-- Merge conditions_updated into conditions
+\set ON_ERROR_STOP 0
+MERGE INTO conditions c
+USING conditions_updated cu
+ON c.time = cu.time AND c.location = cu.location
+WHEN MATCHED THEN
+UPDATE SET temperature = (c.temperature + cu.temperature)/2
+WHEN NOT MATCHED THEN
+INSERT (time, location, temperature) VALUES (cu.time, cu.location, cu.temperature);
+ERROR:  The MERGE command does not support hypertables in this version
+SELECT * FROM conditions ORDER BY time, location ASC;
+             time             | location | temperature 
+------------------------------+----------+-------------
+ Fri Jan 01 00:00:00 2021 PST |        1 |          14
+ Fri Jan 01 00:00:00 2021 PST |        2 |          14
+ Fri Jan 01 00:00:00 2021 PST |        3 |          14
+ Fri Jan 01 00:00:00 2021 PST |        4 |          14
+ Fri Jan 01 00:00:05 2021 PST |        1 |          14
+ Fri Jan 01 00:00:05 2021 PST |        2 |          14
+ Fri Jan 01 00:00:05 2021 PST |        3 |          14
+ Fri Jan 01 00:00:05 2021 PST |        4 |          14
+(8 rows)
+
+\set ON_ERROR_STOP 1

test/sql/CMakeLists.txt

@@ -113,6 +113,10 @@ if((${PG_VERSION_MAJOR} GREATER_EQUAL "14"))
   list(APPEND TEST_FILES ddl_extra.sql)
 endif()
 
+if((${PG_VERSION_MAJOR} GREATER_EQUAL "15"))
+  list(APPEND TEST_FILES merge.sql)
+endif()
+
 # only test custom type if we are in 64-bit architecture
 if("${CMAKE_SIZEOF_VOID_P}" STREQUAL "8")
   list(APPEND TEST_FILES custom_type.sql)

test/sql/merge.sql

@@ -0,0 +1,76 @@
+-- This file and its contents are licensed under the Apache License 2.0.
+-- Please see the included NOTICE for copyright information and
+-- LICENSE-APACHE for a copy of the license.
+
+-- Create conditions table with location and temperature
+DROP TABLE IF EXISTS conditions;
+CREATE TABLE conditions (
+   time        TIMESTAMPTZ       NOT NULL,
+   location    SMALLINT          NOT NULL,
+   temperature DOUBLE PRECISION  NULL
+);
+
+SELECT create_hypertable(
+  'conditions',
+  'time',
+  chunk_time_interval => INTERVAL '5 seconds');
+
+
+INSERT INTO conditions
+SELECT time, location, 14 as temperature
+FROM generate_series(
+	'2021-01-01 00:00:00',
+    '2021-01-01 00:00:09',
+    INTERVAL '5 seconds'
+  ) as time,
+generate_series(1,4) as location;
+
+-- Create conditions_updated table with location and temperature
+DROP TABLE IF EXISTS conditions_updated;
+CREATE TABLE conditions_updated (
+   time        TIMESTAMPTZ       NOT NULL,
+   location    SMALLINT          NOT NULL,
+   temperature DOUBLE PRECISION  NULL
+);
+
+SELECT create_hypertable(
+  'conditions_updated',
+  'time',
+  chunk_time_interval => INTERVAL '5 seconds');
+
+-- Generate data that overlaps with conditions table
+INSERT INTO conditions_updated
+SELECT time, location, 80 as temperature
+FROM generate_series(
+	'2021-01-01 00:00:05',
+    '2021-01-01 00:00:14',
+    INTERVAL '5 seconds'
+  ) as time,
+generate_series(1,4) as location;
+
+-- Print table/rows/num of chunks
+select * from conditions order by time, location asc;
+select * from conditions_updated order by time, location asc;
+select hypertable_name, count(*) as num_of_chunks from timescaledb_information.chunks group by hypertable_name;
+
+-- Print expected values in the conditions table once conditions_updated is merged into it
+-- If a key exists in both tables, we take average of the temperature measured
+-- average logic here is a mess but it works
+SELECT COALESCE(c.time, cu.time) as time,
+       COALESCE(c.location, cu.location) as location,
+       (COALESCE(c.temperature, cu.temperature) + COALESCE(cu.temperature, c.temperature))/2 as temperature 
+FROM conditions AS c FULL JOIN conditions_updated AS cu
+ON c.time = cu.time AND c.location = cu.location;
+
+-- Merge conditions_updated into conditions
+\set ON_ERROR_STOP 0
+MERGE INTO conditions c
+USING conditions_updated cu
+ON c.time = cu.time AND c.location = cu.location
+WHEN MATCHED THEN
+UPDATE SET temperature = (c.temperature + cu.temperature)/2
+WHEN NOT MATCHED THEN
+INSERT (time, location, temperature) VALUES (cu.time, cu.location, cu.temperature);
+
+SELECT * FROM conditions ORDER BY time, location ASC;
+\set ON_ERROR_STOP 1