Fix bug with alter table add/drop column if exists

Previously, an ALTER TABLE ADD COLUMN IF NOT EXISTS on a hypertable
caused an error if the column already did exist. The reversed problem
with DROP COLUMN is also fixed. Resolves issue #42.

Makefile

@@ -35,7 +35,8 @@ SRCS = \
 	src/process_utility.c \
 	src/sort_transform.c \
 	src/insert_chunk_state.c \
-	src/insert_statement_state.c
+	src/insert_statement_state.c \
+	src/ddl_utils.c
 
 OBJS = $(SRCS:.c=.o)
 DEPS = $(SRCS:.c=.d)

sql/common/ddl_utils.sql

@@ -0,0 +1,9 @@
+
+CREATE OR REPLACE FUNCTION ddl_is_add_column(pg_ddl_command)
+  RETURNS bool IMMUTABLE STRICT
+  AS '$libdir/timescaledb' LANGUAGE C;
+
+CREATE OR REPLACE FUNCTION ddl_is_drop_column(pg_ddl_command)
+  RETURNS bool IMMUTABLE STRICT
+  AS '$libdir/timescaledb' LANGUAGE C;
+

sql/load_order.txt

@@ -47,3 +47,4 @@ sql/main/ddl.sql
 sql/main/ddl_triggers.sql
 sql/main/setup_main.sql
 sql/common/permissions.sql
+sql/common/ddl_utils.sql

sql/main/ddl_triggers.sql

@@ -158,28 +158,34 @@ BEGIN
             found_action = FALSE;
 
             --was a column added?
-            FOR att_row IN
-            SELECT *
-            FROM pg_attribute att
-            WHERE attrelid = info.objid AND
+
+            IF ddl_is_add_column(info.command) THEN
+               FOR att_row IN
+               SELECT *
+               FROM pg_attribute att
+               WHERE attrelid = info.objid AND
                   attnum > 0 AND
                   NOT attisdropped AND
                   att.attnum NOT IN (SELECT c.attnum FROM _timescaledb_catalog.hypertable_column c WHERE hypertable_id = hypertable_row.id)
                 LOOP
                     PERFORM  _timescaledb_internal.create_column_from_attribute(hypertable_row.id, att_row);
-                    found_action = TRUE;
                 END LOOP;
 
+            found_action = TRUE;
+            END IF;
+
             --was a column deleted
-            FOR rec IN
-            SELECT name
-            FROM _timescaledb_catalog.hypertable_column c
-            INNER JOIN pg_attribute att ON (attrelid = info.objid AND att.attnum = c.attnum AND attisdropped) --do not match on att.attname here. it gets mangled
-            WHERE hypertable_id = hypertable_row.id
-                LOOP
-                    PERFORM _timescaledb_meta_api.drop_column(hypertable_row.id, rec.name);
-                    found_action = TRUE;
-                END LOOP;
+            IF ddl_is_drop_column(info.command) THEN
+               FOR rec IN
+               SELECT name
+               FROM _timescaledb_catalog.hypertable_column c
+               INNER JOIN pg_attribute att ON (attrelid = info.objid AND att.attnum = c.attnum AND attisdropped) --do not match on att.attname here. it gets mangled
+               WHERE hypertable_id = hypertable_row.id
+                     LOOP
+                         PERFORM _timescaledb_meta_api.drop_column(hypertable_row.id, rec.name);
+                     END LOOP;
+               found_action = TRUE;
+            END IF;
 
             --was a column renamed
             FOR rec IN

src/ddl_utils.c

@@ -0,0 +1,62 @@
+#include <postgres.h>
+#include <tcop/deparse_utility.h>
+
+enum ddl_cmd_type
+{
+	DDL_DROP_COLUMN, DDL_ADD_COLUMN, DDL_OTHER
+};
+
+static enum ddl_cmd_type
+ddl_type_from_cmd(CollectedCommand *cmd)
+{
+	ListCell   *cell;
+
+	if (cmd->type == SCT_AlterTable)
+	{
+		foreach(cell, cmd->d.alterTable.subcmds)
+		{
+			CollectedATSubcmd *sub = lfirst(cell);
+			AlterTableCmd *subcmd = (AlterTableCmd *) sub->parsetree;
+
+			Assert(IsA(subcmd, AlterTableCmd));
+
+			switch (subcmd->subtype)
+			{
+				case AT_AddColumn:
+				case AT_AddColumnRecurse:
+					return DDL_ADD_COLUMN;
+				case AT_DropColumn:
+				case AT_DropColumnRecurse:
+					return DDL_DROP_COLUMN;
+				default:
+					break;
+			}
+		}
+	}
+
+	return DDL_OTHER;
+}
+
+/*
+ * Test if ddl command is an alter table add column
+ */
+PG_FUNCTION_INFO_V1(ddl_is_add_column);
+Datum
+ddl_is_add_column(PG_FUNCTION_ARGS)
+{
+	bool		is_add_column = DDL_ADD_COLUMN == ddl_type_from_cmd((CollectedCommand *) PG_GETARG_POINTER(0));
+
+	PG_RETURN_BOOL(is_add_column);
+}
+
+/*
+ * Test if ddl command is an alter table drop column
+ */
+PG_FUNCTION_INFO_V1(ddl_is_drop_column);
+Datum
+ddl_is_drop_column(PG_FUNCTION_ARGS)
+{
+	bool		is_drop_column = DDL_DROP_COLUMN == ddl_type_from_cmd((CollectedCommand *) PG_GETARG_POINTER(0));
+
+	PG_RETURN_BOOL(is_drop_column);
+}

test/expected/alternate_users.out

@@ -185,6 +185,91 @@ psql:include/ddl_ops_1.sql:61: ERROR:  UPDATE ONLY not supported on hypertables
 DELETE FROM ONLY PUBLIC."Hypertable_1" WHERE "Device_id" = 'dev1';
 psql:include/ddl_ops_1.sql:62: ERROR:  DELETE ONLY not currently supported on hypertables
 \set ON_ERROR_STOP 1
+CREATE TABLE my_ht (time bigint, val integer);
+SELECT * FROM create_hypertable('my_ht', 'time');
+ create_hypertable 
+-------------------
+ 
+(1 row)
+
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should error when adding again
+\set ON_ERROR_STOP 0
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+psql:include/ddl_ops_1.sql:73: ERROR:  column "val2" of relation "my_ht" already exists
+\set ON_ERROR_STOP 1
+-- Should create 
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+psql:include/ddl_ops_1.sql:81: NOTICE:  column "val3" of relation "my_ht" already exists, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should drop
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+psql:include/ddl_ops_1.sql:89: NOTICE:  column "val3" of relation "my_ht" does not exist, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
 \ir include/ddl_ops_2.sql
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN temp_f INTEGER NOT NULL DEFAULT 31;
 ALTER TABLE PUBLIC."Hypertable_1" DROP COLUMN temp_c;
@@ -217,3 +302,4 @@ psql:include/ddl_ops_2.sql:26: ERROR:  CREATE TRIGGER not supported on hypertabl
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_3 BIGINT NOT NULL DEFAULT 131;
 --create column with same name as previously dropped one
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_4 BIGINT NOT NULL DEFAULT 131;
+ 

test/expected/ddl.out

@@ -100,6 +100,91 @@ psql:include/ddl_ops_1.sql:61: ERROR:  UPDATE ONLY not supported on hypertables
 DELETE FROM ONLY PUBLIC."Hypertable_1" WHERE "Device_id" = 'dev1';
 psql:include/ddl_ops_1.sql:62: ERROR:  DELETE ONLY not currently supported on hypertables
 \set ON_ERROR_STOP 1
+CREATE TABLE my_ht (time bigint, val integer);
+SELECT * FROM create_hypertable('my_ht', 'time');
+ create_hypertable 
+-------------------
+ 
+(1 row)
+
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should error when adding again
+\set ON_ERROR_STOP 0
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+psql:include/ddl_ops_1.sql:73: ERROR:  column "val2" of relation "my_ht" already exists
+\set ON_ERROR_STOP 1
+-- Should create 
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+psql:include/ddl_ops_1.sql:81: NOTICE:  column "val3" of relation "my_ht" already exists, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should drop
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+psql:include/ddl_ops_1.sql:89: NOTICE:  column "val3" of relation "my_ht" does not exist, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
 SELECT * FROM PUBLIC."Hypertable_1";
         time         | Device_id | temp_c | humidity | sensor_1 | sensor_2 | sensor_3 | sensor_4 
 ---------------------+-----------+--------+----------+----------+----------+----------+----------
@@ -191,7 +276,8 @@ SELECT * FROM _timescaledb_catalog.default_replica_node;
 ---------------+---------------+------------
  single        |             1 |          0
  single        |             2 |          0
-(2 rows)
+ single        |             3 |          0
+(3 rows)
 
 \ir include/ddl_ops_2.sql
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN temp_f INTEGER NOT NULL DEFAULT 31;
@@ -225,6 +311,7 @@ psql:include/ddl_ops_2.sql:26: ERROR:  CREATE TRIGGER not supported on hypertabl
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_3 BIGINT NOT NULL DEFAULT 131;
 --create column with same name as previously dropped one
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_4 BIGINT NOT NULL DEFAULT 131;
+ 
 \d+ PUBLIC."Hypertable_1"
                                 Table "public.Hypertable_1"
       Column      |  Type   |      Modifiers       | Storage  | Stats target | Description 

test/expected/ddl_single.out

@@ -100,6 +100,91 @@ psql:include/ddl_ops_1.sql:61: ERROR:  UPDATE ONLY not supported on hypertables
 DELETE FROM ONLY PUBLIC."Hypertable_1" WHERE "Device_id" = 'dev1';
 psql:include/ddl_ops_1.sql:62: ERROR:  DELETE ONLY not currently supported on hypertables
 \set ON_ERROR_STOP 1
+CREATE TABLE my_ht (time bigint, val integer);
+SELECT * FROM create_hypertable('my_ht', 'time');
+ create_hypertable 
+-------------------
+ 
+(1 row)
+
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should error when adding again
+\set ON_ERROR_STOP 0
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+psql:include/ddl_ops_1.sql:73: ERROR:  column "val2" of relation "my_ht" already exists
+\set ON_ERROR_STOP 1
+-- Should create 
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+psql:include/ddl_ops_1.sql:81: NOTICE:  column "val3" of relation "my_ht" already exists, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+ val3   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should drop
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
+-- Should skip and not error
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+psql:include/ddl_ops_1.sql:89: NOTICE:  column "val3" of relation "my_ht" does not exist, skipping
+\d my_ht
+     Table "public.my_ht"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ time   | bigint  | 
+ val    | integer | 
+ val2   | integer | 
+Triggers:
+    _timescaledb_main_after_insert_trigger AFTER INSERT ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.main_table_after_insert_trigger()
+    _timescaledb_main_insert_trigger BEFORE INSERT ON my_ht FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.main_table_insert_trigger()
+    _timescaledb_modify_trigger BEFORE DELETE OR UPDATE ON my_ht FOR EACH STATEMENT EXECUTE PROCEDURE _timescaledb_internal.on_unsupported_main_table()
+
 SELECT * FROM PUBLIC."Hypertable_1";
         time         | Device_id | temp_c | humidity | sensor_1 | sensor_2 | sensor_3 | sensor_4 
 ---------------------+-----------+--------+----------+----------+----------+----------+----------
@@ -120,7 +205,8 @@ SELECT * FROM _timescaledb_catalog.default_replica_node;
 ---------------+---------------+------------
  single        |             1 |          0
  single        |             2 |          0
-(2 rows)
+ single        |             3 |          0
+(3 rows)
 
 \ir include/ddl_ops_2.sql
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN temp_f INTEGER NOT NULL DEFAULT 31;
@@ -154,6 +240,7 @@ psql:include/ddl_ops_2.sql:26: ERROR:  CREATE TRIGGER not supported on hypertabl
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_3 BIGINT NOT NULL DEFAULT 131;
 --create column with same name as previously dropped one
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_4 BIGINT NOT NULL DEFAULT 131;
+ 
 \d+ PUBLIC."Hypertable_1"
                                 Table "public.Hypertable_1"
       Column      |  Type   |      Modifiers       | Storage  | Stats target | Description 

test/sql/include/ddl_ops_1.sql

@@ -61,3 +61,30 @@ CREATE UNIQUE INDEX "Unique2" ON PUBLIC."Hypertable_1" (sensor_1);
 UPDATE ONLY PUBLIC."Hypertable_1" SET time = 0 WHERE TRUE;
 DELETE FROM ONLY PUBLIC."Hypertable_1" WHERE "Device_id" = 'dev1';
 \set ON_ERROR_STOP 1
+
+
+CREATE TABLE my_ht (time bigint, val integer);
+SELECT * FROM create_hypertable('my_ht', 'time');
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+\d my_ht
+
+-- Should error when adding again
+\set ON_ERROR_STOP 0
+ALTER TABLE my_ht ADD COLUMN val2 integer;
+\set ON_ERROR_STOP 1
+
+-- Should create 
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+\d my_ht
+
+-- Should skip and not error
+ALTER TABLE my_ht ADD COLUMN IF NOT EXISTS val3 integer;
+\d my_ht
+
+-- Should drop
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+\d my_ht
+
+-- Should skip and not error
+ALTER TABLE my_ht DROP COLUMN IF EXISTS val3;
+\d my_ht

test/sql/include/ddl_ops_2.sql

@@ -30,5 +30,4 @@ FOR EACH STATEMENT EXECUTE PROCEDURE empty_trigger_func();
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_3 BIGINT NOT NULL DEFAULT 131;
 --create column with same name as previously dropped one
 ALTER TABLE PUBLIC."Hypertable_1" ADD COLUMN sensor_4 BIGINT NOT NULL DEFAULT 131;
-
-
+