Prevent excluding system and non-existent columns.

expected/excluded_columns.out

@@ -1,9 +1,22 @@
+SELECT setting::integer < 90600 AS pre_96
+FROM pg_settings WHERE name = 'server_version_num';
+ pre_96 
+--------
+ f
+(1 row)
+
 CREATE TABLE excl (
     value text NOT NULL,
     null_value integer,
     flap text NOT NULL
 );
-SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['flap']);
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['xmin']); -- fails
+ERROR:  cannot exclude system column "xmin"
+CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 316 at RAISE
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['none']); -- fails
+ERROR:  column "none" does not exist
+CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 306 at RAISE
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['flap']); -- passes
  add_system_time_period 
 ------------------------
  t

expected/excluded_columns_1.out

@@ -0,0 +1,97 @@
+SELECT setting::integer < 90600 AS pre_96
+FROM pg_settings WHERE name = 'server_version_num';
+ pre_96 
+--------
+ t
+(1 row)
+
+CREATE TABLE excl (
+    value text NOT NULL,
+    null_value integer,
+    flap text NOT NULL
+);
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['xmin']); -- fails
+ERROR:  cannot exclude system column "xmin"
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['none']); -- fails
+ERROR:  column "none" does not exist
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['flap']); -- passes
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+SELECT periods.add_system_versioning('excl');
+NOTICE:  history table "excl_history" created for "excl", be sure to index it properly
+ add_system_versioning 
+-----------------------
+
+(1 row)
+
+TABLE periods.periods;
+ table_name | period_name | start_column_name | end_column_name | range_type | bounds_check_constraint 
+------------+-------------+-------------------+-----------------+------------+-------------------------
+ excl       | system_time | system_time_start | system_time_end | tstzrange  | excl_system_time_check
+(1 row)
+
+TABLE periods.system_time_periods;
+ table_name | period_name |      infinity_check_constraint      |     generated_always_trigger      |     write_history_trigger      | truncate_trigger | excluded_column_names 
+------------+-------------+-------------------------------------+-----------------------------------+--------------------------------+------------------+-----------------------
+ excl       | system_time | excl_system_time_end_infinity_check | excl_system_time_generated_always | excl_system_time_write_history | excl_truncate    | {flap}
+(1 row)
+
+TABLE periods.system_versioning;
+ table_name | period_name | history_table_name |     view_name     |              func_as_of               |                           func_between                           |                           func_between_symmetric                           |                           func_from_to                           
+------------+-------------+--------------------+-------------------+---------------------------------------+------------------------------------------------------------------+----------------------------------------------------------------------------+------------------------------------------------------------------
+ excl       | system_time | excl_history       | excl_with_history | excl__as_of(timestamp with time zone) | excl__between(timestamp with time zone,timestamp with time zone) | excl__between_symmetric(timestamp with time zone,timestamp with time zone) | excl__from_to(timestamp with time zone,timestamp with time zone)
+(1 row)
+
+BEGIN;
+SELECT CURRENT_TIMESTAMP AS now \gset
+INSERT INTO excl (value, flap) VALUES ('hello world', 'off');
+COMMIT;
+SELECT value, null_value, flap, system_time_start <> :'now' AS changed FROM excl;
+    value    | null_value | flap | changed 
+-------------+------------+------+---------
+ hello world |            | off  | f
+(1 row)
+
+UPDATE excl SET flap = 'off';
+UPDATE excl SET flap = 'on';
+UPDATE excl SET flap = 'off';
+UPDATE excl SET flap = 'on';
+SELECT value, null_value, flap, system_time_start <> :'now' AS changed FROM excl;
+    value    | null_value | flap | changed 
+-------------+------------+------+---------
+ hello world |            | on   | f
+(1 row)
+
+BEGIN;
+SELECT CURRENT_TIMESTAMP AS now2 \gset
+UPDATE excl SET value = 'howdy folks!';
+COMMIT;
+SELECT value, null_value, flap, system_time_start <> :'now' AS changed FROM excl;
+    value     | null_value | flap | changed 
+--------------+------------+------+---------
+ howdy folks! |            | on   | t
+(1 row)
+
+UPDATE excl SET null_value = 0;
+SELECT value, null_value, flap, system_time_start <> :'now2' AS changed FROM excl;
+    value     | null_value | flap | changed 
+--------------+------------+------+---------
+ howdy folks! |          0 | on   | t
+(1 row)
+
+SELECT periods.drop_system_versioning('excl');
+ drop_system_versioning 
+------------------------
+ t
+(1 row)
+
+SELECT periods.drop_system_time_period('excl');
+ drop_system_time_period 
+-------------------------
+ t
+(1 row)
+
+DROP TABLE excl;

expected/health_checks.out

@@ -12,7 +12,7 @@ ERROR:  table "log" must be persistent
 CONTEXT:  PL/pgSQL function periods.add_period(regclass,name,name,name,regtype,name) line 72 at RAISE
 SELECT periods.add_system_time_period('log'); -- fails
 ERROR:  table "log" must be persistent
-CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 72 at RAISE
+CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 74 at RAISE
 ALTER TABLE log SET LOGGED;
 SELECT periods.add_period('log', 'p', 's', 'e'); -- passes
  add_period 

expected/system_time_periods.out

@@ -222,7 +222,7 @@ SELECT periods.add_unique_key('no_unique', ARRAY['system_time_end'], 'p'); -- pa
 
 SELECT periods.add_system_time_period('no_unique'); -- fails
 ERROR:  columns in period for SYSTEM_TIME are not allowed in UNIQUE keys
-CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 46 at RAISE
+CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 48 at RAISE
 SELECT periods.drop_unique_key('no_unique', 'no_unique_system_time_start_p');
  drop_unique_key 
 -----------------
@@ -278,5 +278,5 @@ SELECT periods.add_foreign_key('no_unique_ref', ARRAY['system_time_end'], 'q', '
 
 SELECT periods.add_system_time_period('no_unique_ref'); -- fails
 ERROR:  columns for SYSTEM_TIME must not be part of foreign keys
-CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 166 at RAISE
+CONTEXT:  PL/pgSQL function periods.add_system_time_period(regclass,name,name,name,name,name,name,name,name[]) line 168 at RAISE
 DROP TABLE no_unique, no_unique_ref;

periods--1.0--1.1.sql

@@ -37,6 +37,8 @@ DECLARE
     end_collation oid;
     end_notnull boolean;
 
+    excluded_column_name name;
+
     DATE_OID CONSTANT integer := 1082;
     TIMESTAMP_OID CONSTANT integer := 1114;
     TIMESTAMPTZ_OID CONSTANT integer := 1184;
@@ -311,6 +313,27 @@ BEGIN
         END IF;
     END IF;
 
+    /* Make sure all the excluded columns exist */
+    FOR excluded_column_name IN
+        SELECT u.name
+        FROM unnest(excluded_column_names) AS u (name)
+        WHERE NOT EXISTS (
+            SELECT FROM pg_catalog.pg_attribute AS a
+            WHERE (a.attrelid, a.attname) = (table_class, u.name))
+    LOOP
+        RAISE EXCEPTION 'column "%" does not exist', excluded_column_name;
+    END LOOP;
+
+    /* Don't allow system columns to be excluded either */
+    FOR excluded_column_name IN
+        SELECT u.name
+        FROM unnest(excluded_column_names) AS u (name)
+        JOIN pg_catalog.pg_attribute AS a ON (a.attrelid, a.attname) = (table_class, u.name)
+        WHERE a.attnum < 0
+    LOOP
+        RAISE EXCEPTION 'cannot exclude system column "%"', excluded_column_name;
+    END LOOP;
+
     generated_always_trigger := coalesce(
         generated_always_trigger,
         periods._choose_name(ARRAY[table_name], 'system_time_generated_always'));

sql/excluded_columns.sql

@@ -1,9 +1,14 @@
+SELECT setting::integer < 90600 AS pre_96
+FROM pg_settings WHERE name = 'server_version_num';
+
 CREATE TABLE excl (
     value text NOT NULL,
     null_value integer,
     flap text NOT NULL
 );
-SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['flap']);
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['xmin']); -- fails
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['none']); -- fails
+SELECT periods.add_system_time_period('excl', excluded_column_names => ARRAY['flap']); -- passes
 SELECT periods.add_system_versioning('excl');
 
 TABLE periods.periods;