Allow SYSTEM_TIME columns to be date, timestamp, and timestamptz.

The SQL standard provides rules for these types, so let's implement them.
xocolatl · Jul 17, 2019 · 939fccf · 939fccf
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diff --git a/README.md b/README.md
@@ -152,11 +152,17 @@ here. You can use the range type operators instead.
 ## `SYSTEM_TIME`
 
 If the period is named `SYSTEM_TIME`, then special rules apply. The type
-of the columns must be `timestamp with time zone` and they are not
-modifyable by the user. In the SQL standard, the start column is
-`GENERATED ALWAYS AS ROW START` and the end column is `GENERATED ALWAYS
-AS ROW END`. This extension uses triggers to set the start column to
-`transaction_timestamp()` and the end column is always `'infinity'`.
+of the columns must be `date`, `timestamp without time zone`, or
+`timestamp with time zone`; and they are not modifiable by the user. In
+the SQL standard, the start column is `GENERATED ALWAYS AS ROW START`
+and the end column is `GENERATED ALWAYS AS ROW END`. This extension uses
+triggers to set the start column to `transaction_timestamp()` and the
+end column is always `'infinity'`.
+
+***Note:*** It is generally unwise to use anything but `timestamp with
+time zone` because changes in the `TimeZone` configuration paramater or
+even just Daylight Savings Time changes can distort the history. Even
+when only using UTC, we recommend the `timestamp with time zone` type.
 
 ``` sql
 CREATE TABLE example (

diff --git a/expected/periods.out b/expected/periods.out
@@ -287,6 +287,78 @@ TABLE periods.for_portion_views;
 (0 rows)
 
 DROP TABLE pricing;
+/* SYSTEM_TIME with date */
+BEGIN;
+SELECT transaction_timestamp()::date AS xd,
+       transaction_timestamp()::timestamp AS xts,
+       transaction_timestamp() AS xtstz
+\gset
+CREATE TABLE sysver_date (val text, start_date date, end_date date);
+SELECT periods.add_system_time_period('sysver_date', 'start_date', 'end_date');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_date | system_time | start_date        | end_date        | daterange  | sysver_date_system_time_check
+(1 row)
+
+INSERT INTO sysver_date DEFAULT VALUES;
+SELECT val, start_date = :'xd' AS start_date_eq, end_date FROM sysver_date;
+ val | start_date_eq | end_date 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_date;
+/* SYSTEM_TIME with timestamp without time zone */
+CREATE TABLE sysver_ts (val text, start_ts timestamp without time zone, end_ts timestamp without time zone);
+SELECT periods.add_system_time_period('sysver_ts', 'start_ts', 'end_ts');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name | period_name | start_column_name | end_column_name | range_type |   bounds_check_constraint   
+------------+-------------+-------------------+-----------------+------------+-----------------------------
+ sysver_ts  | system_time | start_ts          | end_ts          | tsrange    | sysver_ts_system_time_check
+(1 row)
+
+INSERT INTO sysver_ts DEFAULT VALUES;
+SELECT val, start_ts = :'xts' AS start_ts_eq, end_ts FROM sysver_ts;
+ val | start_ts_eq |  end_ts  
+-----+-------------+----------
+     | t           | infinity
+(1 row)
+
+DROP TABLE sysver_ts;
+/* SYSTEM_TIME with timestamp with time zone */
+CREATE TABLE sysver_tstz (val text, start_tstz timestamp with time zone, end_tstz timestamp with time zone);
+SELECT periods.add_system_time_period('sysver_tstz', 'start_tstz', 'end_tstz');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_tstz | system_time | start_tstz        | end_tstz        | tstzrange  | sysver_tstz_system_time_check
+(1 row)
+
+INSERT INTO sysver_tstz DEFAULT VALUES;
+SELECT val, start_tstz = :'xtstz' AS start_tstz_eq, end_tstz FROM sysver_tstz;
+ val | start_tstz_eq | end_tstz 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_tstz;
+COMMIT;
 /* Basic SYSTEM_TIME periods with CASCADE/purge */
 CREATE TABLE sysver (val text);
 SELECT periods.add_system_time_period('sysver', 'startname');

diff --git a/expected/periods_1.out b/expected/periods_1.out
@@ -289,6 +289,78 @@ TABLE periods.for_portion_views;
 (0 rows)
 
 DROP TABLE pricing;
+/* SYSTEM_TIME with date */
+BEGIN;
+SELECT transaction_timestamp()::date AS xd,
+       transaction_timestamp()::timestamp AS xts,
+       transaction_timestamp() AS xtstz
+\gset
+CREATE TABLE sysver_date (val text, start_date date, end_date date);
+SELECT periods.add_system_time_period('sysver_date', 'start_date', 'end_date');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_date | system_time | start_date        | end_date        | daterange  | sysver_date_system_time_check
+(1 row)
+
+INSERT INTO sysver_date DEFAULT VALUES;
+SELECT val, start_date = :'xd' AS start_date_eq, end_date FROM sysver_date;
+ val | start_date_eq | end_date 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_date;
+/* SYSTEM_TIME with timestamp without time zone */
+CREATE TABLE sysver_ts (val text, start_ts timestamp without time zone, end_ts timestamp without time zone);
+SELECT periods.add_system_time_period('sysver_ts', 'start_ts', 'end_ts');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name | period_name | start_column_name | end_column_name | range_type |   bounds_check_constraint   
+------------+-------------+-------------------+-----------------+------------+-----------------------------
+ sysver_ts  | system_time | start_ts          | end_ts          | tsrange    | sysver_ts_system_time_check
+(1 row)
+
+INSERT INTO sysver_ts DEFAULT VALUES;
+SELECT val, start_ts = :'xts' AS start_ts_eq, end_ts FROM sysver_ts;
+ val | start_ts_eq |  end_ts  
+-----+-------------+----------
+     | t           | infinity
+(1 row)
+
+DROP TABLE sysver_ts;
+/* SYSTEM_TIME with timestamp with time zone */
+CREATE TABLE sysver_tstz (val text, start_tstz timestamp with time zone, end_tstz timestamp with time zone);
+SELECT periods.add_system_time_period('sysver_tstz', 'start_tstz', 'end_tstz');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_tstz | system_time | start_tstz        | end_tstz        | tstzrange  | sysver_tstz_system_time_check
+(1 row)
+
+INSERT INTO sysver_tstz DEFAULT VALUES;
+SELECT val, start_tstz = :'xtstz' AS start_tstz_eq, end_tstz FROM sysver_tstz;
+ val | start_tstz_eq | end_tstz 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_tstz;
+COMMIT;
 /* Basic SYSTEM_TIME periods with CASCADE/purge */
 CREATE TABLE sysver (val text);
 SELECT periods.add_system_time_period('sysver', 'startname');

diff --git a/expected/periods_2.out b/expected/periods_2.out
@@ -291,6 +291,78 @@ TABLE periods.for_portion_views;
 (0 rows)
 
 DROP TABLE pricing;
+/* SYSTEM_TIME with date */
+BEGIN;
+SELECT transaction_timestamp()::date AS xd,
+       transaction_timestamp()::timestamp AS xts,
+       transaction_timestamp() AS xtstz
+\gset
+CREATE TABLE sysver_date (val text, start_date date, end_date date);
+SELECT periods.add_system_time_period('sysver_date', 'start_date', 'end_date');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_date | system_time | start_date        | end_date        | daterange  | sysver_date_system_time_check
+(1 row)
+
+INSERT INTO sysver_date DEFAULT VALUES;
+SELECT val, start_date = :'xd' AS start_date_eq, end_date FROM sysver_date;
+ val | start_date_eq | end_date 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_date;
+/* SYSTEM_TIME with timestamp without time zone */
+CREATE TABLE sysver_ts (val text, start_ts timestamp without time zone, end_ts timestamp without time zone);
+SELECT periods.add_system_time_period('sysver_ts', 'start_ts', 'end_ts');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name | period_name | start_column_name | end_column_name | range_type |   bounds_check_constraint   
+------------+-------------+-------------------+-----------------+------------+-----------------------------
+ sysver_ts  | system_time | start_ts          | end_ts          | tsrange    | sysver_ts_system_time_check
+(1 row)
+
+INSERT INTO sysver_ts DEFAULT VALUES;
+SELECT val, start_ts = :'xts' AS start_ts_eq, end_ts FROM sysver_ts;
+ val | start_ts_eq |  end_ts  
+-----+-------------+----------
+     | t           | infinity
+(1 row)
+
+DROP TABLE sysver_ts;
+/* SYSTEM_TIME with timestamp with time zone */
+CREATE TABLE sysver_tstz (val text, start_tstz timestamp with time zone, end_tstz timestamp with time zone);
+SELECT periods.add_system_time_period('sysver_tstz', 'start_tstz', 'end_tstz');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_tstz | system_time | start_tstz        | end_tstz        | tstzrange  | sysver_tstz_system_time_check
+(1 row)
+
+INSERT INTO sysver_tstz DEFAULT VALUES;
+SELECT val, start_tstz = :'xtstz' AS start_tstz_eq, end_tstz FROM sysver_tstz;
+ val | start_tstz_eq | end_tstz 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_tstz;
+COMMIT;
 /* Basic SYSTEM_TIME periods with CASCADE/purge */
 CREATE TABLE sysver (val text);
 SELECT periods.add_system_time_period('sysver', 'startname');

diff --git a/expected/periods_3.out b/expected/periods_3.out
@@ -285,6 +285,78 @@ TABLE periods.for_portion_views;
 (0 rows)
 
 DROP TABLE pricing;
+/* SYSTEM_TIME with date */
+BEGIN;
+SELECT transaction_timestamp()::date AS xd,
+       transaction_timestamp()::timestamp AS xts,
+       transaction_timestamp() AS xtstz
+\gset
+CREATE TABLE sysver_date (val text, start_date date, end_date date);
+SELECT periods.add_system_time_period('sysver_date', 'start_date', 'end_date');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_date | system_time | start_date        | end_date        | daterange  | sysver_date_system_time_check
+(1 row)
+
+INSERT INTO sysver_date DEFAULT VALUES;
+SELECT val, start_date = :'xd' AS start_date_eq, end_date FROM sysver_date;
+ val | start_date_eq | end_date 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_date;
+/* SYSTEM_TIME with timestamp without time zone */
+CREATE TABLE sysver_ts (val text, start_ts timestamp without time zone, end_ts timestamp without time zone);
+SELECT periods.add_system_time_period('sysver_ts', 'start_ts', 'end_ts');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name | period_name | start_column_name | end_column_name | range_type |   bounds_check_constraint   
+------------+-------------+-------------------+-----------------+------------+-----------------------------
+ sysver_ts  | system_time | start_ts          | end_ts          | tsrange    | sysver_ts_system_time_check
+(1 row)
+
+INSERT INTO sysver_ts DEFAULT VALUES;
+SELECT val, start_ts = :'xts' AS start_ts_eq, end_ts FROM sysver_ts;
+ val | start_ts_eq |  end_ts  
+-----+-------------+----------
+     | t           | infinity
+(1 row)
+
+DROP TABLE sysver_ts;
+/* SYSTEM_TIME with timestamp with time zone */
+CREATE TABLE sysver_tstz (val text, start_tstz timestamp with time zone, end_tstz timestamp with time zone);
+SELECT periods.add_system_time_period('sysver_tstz', 'start_tstz', 'end_tstz');
+ add_system_time_period 
+------------------------
+ t
+(1 row)
+
+TABLE periods.periods;
+ table_name  | period_name | start_column_name | end_column_name | range_type |    bounds_check_constraint    
+-------------+-------------+-------------------+-----------------+------------+-------------------------------
+ sysver_tstz | system_time | start_tstz        | end_tstz        | tstzrange  | sysver_tstz_system_time_check
+(1 row)
+
+INSERT INTO sysver_tstz DEFAULT VALUES;
+SELECT val, start_tstz = :'xtstz' AS start_tstz_eq, end_tstz FROM sysver_tstz;
+ val | start_tstz_eq | end_tstz 
+-----+---------------+----------
+     | t             | infinity
+(1 row)
+
+DROP TABLE sysver_tstz;
+COMMIT;
 /* Basic SYSTEM_TIME periods with CASCADE/purge */
 CREATE TABLE sysver (val text);
 SELECT periods.add_system_time_period('sysver', 'startname');

diff --git a/periods--0.03.sql b/periods--0.03.sql
@@ -567,6 +567,11 @@ DECLARE
     end_type oid;
     end_collation oid;
     end_notnull boolean;
+
+    DATE_OID CONSTANT integer := 1082;
+    TIMESTAMP_OID CONSTANT integer := 1114;
+    TIMESTAMPTZ_OID CONSTANT integer := 1184;
+    range_type regtype;
 BEGIN
     IF table_class IS NULL THEN
         RAISE EXCEPTION 'no table name specified';
@@ -679,10 +684,22 @@ BEGIN
     END IF;
 
     /* Verify compatibility of start/end columns */
-    IF start_type <> 'timestamp with time zone'::regtype OR end_type <> 'timestamp with time zone'::regtype THEN
-        RAISE EXCEPTION 'start and end columns must be of type "timestamp with time zone"';
+    IF start_type::regtype NOT IN ('date', 'timestamp without time zone', 'timestamp with time zone') THEN
+        RAISE EXCEPTION 'SYSTEM_TIME periods must be of type "date", "timestamp without time zone", or "timestamp with time zone"';
+    END IF;
+    IF start_type <> end_type THEN
+        RAISE EXCEPTION 'start and end columns must be of same type';
     END IF;
 
+    /* Get appropriate range type */
+    CASE start_type
+        WHEN DATE_OID THEN range_type := 'daterange';
+        WHEN TIMESTAMP_OID THEN range_type := 'tsrange';
+        WHEN TIMESTAMPTZ_OID THEN range_type := 'tstzrange';
+    ELSE
+        RAISE EXCEPTION 'unexpected data type: "%"', start_type::regtype;
+    END CASE;
+
     /* can't be part of a foreign key */
     IF EXISTS (
         SELECT FROM periods.foreign_keys AS fk
@@ -767,7 +784,7 @@ BEGIN
     EXECUTE format('CREATE TRIGGER %I AFTER TRUNCATE ON %s FOR EACH STATEMENT EXECUTE PROCEDURE periods.truncate_system_versioning()', truncate_trigger, table_class);
 
     INSERT INTO periods.periods (table_name, period_name, start_column_name, end_column_name, range_type, bounds_check_constraint)
-    VALUES (table_class, period_name, start_column_name, end_column_name, 'tstzrange', bounds_check_constraint);
+    VALUES (table_class, period_name, start_column_name, end_column_name, range_type, bounds_check_constraint);
 
     INSERT INTO periods.system_time_periods (table_name, period_name, infinity_check_constraint, generated_always_trigger, write_history_trigger, truncate_trigger)
     VALUES (table_class, period_name, infinity_check_constraint, generated_always_trigger, write_history_trigger, truncate_trigger);