Move time_bucket epoch to a Monday

Since Monday is the ISO start of the week, it makes sense to move
the time_bucket epoch to start on a Monday. Before the epoch was the
same as the Postgres epoch (2000-01-01, a Saturday).

src/utils.c

@@ -283,10 +283,24 @@ ts_timestamp_bucket(PG_FUNCTION_ARGS)
 	Timestamp	timestamp = PG_GETARG_TIMESTAMP(1);
 	Timestamp	result;
 	int64		period = -1;
+	/* The offset moves the epoch to start on a monday the default postgres epoch starts on a saturday.
+	 * This makes time-buckets by a week more intuitive.
+	 */
+#ifdef HAVE_INT64_TIMESTAMP
+	int64 offset = 2*USECS_PER_DAY;
+#else
+	double offset = 2*SECS_PER_DAY;
+#endif
 
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 		PG_RETURN_TIMESTAMP(timestamp);
 
+	if(timestamp < DT_NOBEGIN + offset)
+		ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				errmsg("timestamp out of range")));
+	timestamp -= offset;
+
 	period = get_interval_period_timestamp_units(interval);
 	/* result = (timestamp / period) * period */
 	TMODULO(timestamp, result, period);
@@ -304,6 +318,7 @@ ts_timestamp_bucket(PG_FUNCTION_ARGS)
 	{
 		result *= period;
 	}
+	result += offset;
 	PG_RETURN_TIMESTAMP(result);
 }
 
@@ -315,10 +330,25 @@ ts_timestamptz_bucket(PG_FUNCTION_ARGS)
 	TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
 	TimestampTz result;
 	int64		period = -1;
+	/* The offset moves the epoch to start on a monday the default postgres epoch starts on a saturday.
+	 * This makes time-buckets by a week more intuitive.
+	 */
+	#ifdef HAVE_INT64_TIMESTAMP
+		int64 offset = 2*USECS_PER_DAY;
+	#else
+		double offset = 2*SECS_PER_DAY;
+	#endif
 
 	if (TIMESTAMP_NOT_FINITE(timestamp))
 		PG_RETURN_TIMESTAMPTZ(timestamp);
 
+	if(timestamp < DT_NOBEGIN + offset)
+		ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				errmsg("timestamp out of range")));
+
+	timestamp -= offset;
+
 	period = get_interval_period_timestamp_units(interval);
 	/* result = (timestamp / period) * period */
 	TMODULO(timestamp, result, period);
@@ -336,6 +366,7 @@ ts_timestamptz_bucket(PG_FUNCTION_ARGS)
 	{
 		result *= period;
 	}
+	result += offset;
 	PG_RETURN_TIMESTAMPTZ(result);
 }
 

test/expected/append.out

@@ -404,12 +404,12 @@ psql:include/append.sql:166: NOTICE:  Stable function now_s() called!
 psql:include/append.sql:166: NOTICE:  Stable function now_s() called!
             btime             | value 
 ------------------------------+-------
- Wed Mar 01 16:00:00 2017 PST |  22.5
+ Fri Mar 03 16:00:00 2017 PST |  22.5
- Fri Mar 31 17:00:00 2017 PDT |      
+ Sun Apr 02 17:00:00 2017 PDT |      
- Sun Apr 30 17:00:00 2017 PDT |  25.7
+ Tue May 02 17:00:00 2017 PDT |  25.7
- Tue May 30 17:00:00 2017 PDT |      
+ Thu Jun 01 17:00:00 2017 PDT |      
- Thu Jun 29 17:00:00 2017 PDT |      
+ Sat Jul 01 17:00:00 2017 PDT |      
- Sat Jul 29 17:00:00 2017 PDT |  34.1
+ Mon Jul 31 17:00:00 2017 PDT |  34.1
 (6 rows)
 
 -- Create another hypertable to join with

test/expected/append_unoptimized.out

@@ -434,12 +434,12 @@ psql:include/append.sql:166: NOTICE:  Stable function now_s() called!
 psql:include/append.sql:166: NOTICE:  Stable function now_s() called!
             btime             | value 
 ------------------------------+-------
- Wed Mar 01 16:00:00 2017 PST |  22.5
+ Fri Mar 03 16:00:00 2017 PST |  22.5
- Fri Mar 31 17:00:00 2017 PDT |      
+ Sun Apr 02 17:00:00 2017 PDT |      
- Sun Apr 30 17:00:00 2017 PDT |  25.7
+ Tue May 02 17:00:00 2017 PDT |  25.7
- Tue May 30 17:00:00 2017 PDT |      
+ Thu Jun 01 17:00:00 2017 PDT |      
- Thu Jun 29 17:00:00 2017 PDT |      
+ Sat Jul 01 17:00:00 2017 PDT |      
- Sat Jul 29 17:00:00 2017 PDT |  34.1
+ Mon Jul 31 17:00:00 2017 PDT |  34.1
 (6 rows)
 
 -- Create another hypertable to join with

test/expected/timestamp.out

@@ -677,21 +677,6 @@ FROM unnest(ARRAY[
 (2 rows)
 
 SELECT time, time_bucket(INTERVAL '4 day', time::date)
-FROM unnest(ARRAY[
-    date '2017-11-02',
-    date '2017-11-03',
-    date '2017-11-06',
-    date '2017-11-07'
-    ]) AS time;
-    time    | time_bucket 
-------------+-------------
- 11-02-2017 | 10-30-2017
- 11-03-2017 | 11-03-2017
- 11-06-2017 | 11-03-2017
- 11-07-2017 | 11-07-2017
-(4 rows)
-
-SELECT time, time_bucket(INTERVAL '4 day', time::date, INTERVAL '2 day')
 FROM unnest(ARRAY[
     date '2017-11-04',
     date '2017-11-05',
@@ -706,6 +691,100 @@ FROM unnest(ARRAY[
  11-09-2017 | 11-09-2017
 (4 rows)
 
+SELECT time, time_bucket(INTERVAL '4 day', time::date, INTERVAL '2 day')
+FROM unnest(ARRAY[
+    date '2017-11-06',
+    date '2017-11-07',
+    date '2017-11-10',
+    date '2017-11-11'
+    ]) AS time;
+    time    | time_bucket 
+------------+-------------
+ 11-06-2017 | 11-03-2017
+ 11-07-2017 | 11-07-2017
+ 11-10-2017 | 11-07-2017
+ 11-11-2017 | 11-11-2017
+(4 rows)
+
+-- 2019-09-24 is a Monday.
+SELECT time, time_bucket(INTERVAL '1 week', time::date)
+FROM unnest(ARRAY[
+    date '2018-09-16',
+    date '2018-09-17',
+    date '2018-09-23',
+    date '2018-09-24'
+    ]) AS time;
+    time    | time_bucket 
+------------+-------------
+ 09-16-2018 | 09-10-2018
+ 09-17-2018 | 09-17-2018
+ 09-23-2018 | 09-17-2018
+ 09-24-2018 | 09-24-2018
+(4 rows)
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '2018-09-16',
+    timestamp without time zone '2018-09-17',
+    timestamp without time zone '2018-09-23',
+    timestamp without time zone '2018-09-24'
+    ]) AS time;
+           time           |       time_bucket        
+--------------------------+--------------------------
+ Sun Sep 16 00:00:00 2018 | Mon Sep 10 00:00:00 2018
+ Mon Sep 17 00:00:00 2018 | Mon Sep 17 00:00:00 2018
+ Sun Sep 23 00:00:00 2018 | Mon Sep 17 00:00:00 2018
+ Mon Sep 24 00:00:00 2018 | Mon Sep 24 00:00:00 2018
+(4 rows)
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp with time zone '2018-09-16',
+    timestamp with time zone '2018-09-17',
+    timestamp with time zone '2018-09-23',
+    timestamp with time zone '2018-09-24'
+    ]) AS time;
+             time             |         time_bucket          
+------------------------------+------------------------------
+ Sun Sep 16 00:00:00 2018 EDT | Sun Sep 09 20:00:00 2018 EDT
+ Mon Sep 17 00:00:00 2018 EDT | Sun Sep 16 20:00:00 2018 EDT
+ Sun Sep 23 00:00:00 2018 EDT | Sun Sep 16 20:00:00 2018 EDT
+ Mon Sep 24 00:00:00 2018 EDT | Sun Sep 23 20:00:00 2018 EDT
+(4 rows)
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp with time zone '-Infinity',
+    timestamp with time zone 'Infinity'
+    ]) AS time;
+   time    | time_bucket 
+-----------+-------------
+ -infinity | -infinity
+ infinity  | infinity
+(2 rows)
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '-Infinity',
+    timestamp without time zone 'Infinity'
+    ]) AS time;
+   time    | time_bucket 
+-----------+-------------
+ -infinity | -infinity
+ infinity  | infinity
+(2 rows)
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '4714-11-24 01:01:01.0 BC',
+    timestamp without time zone '294276-12-31 23:59:59.9999'
+    ]) AS time;
+              time               |         time_bucket         
+---------------------------------+-----------------------------
+ Mon Nov 24 01:01:01 4714 BC     | Mon Nov 24 00:00:00 4714 BC
+ Sun Dec 31 23:59:59.9999 294276 | Mon Dec 25 00:00:00 294276
+(2 rows)
+
 -------------------------------------
 --- Test time input functions --
 -------------------------------------

test/sql/timestamp.sql

@@ -400,14 +400,6 @@ FROM unnest(ARRAY[
     ]) AS time;
 
 SELECT time, time_bucket(INTERVAL '4 day', time::date)
-FROM unnest(ARRAY[
-    date '2017-11-02',
-    date '2017-11-03',
-    date '2017-11-06',
-    date '2017-11-07'
-    ]) AS time;
-
-SELECT time, time_bucket(INTERVAL '4 day', time::date, INTERVAL '2 day')
 FROM unnest(ARRAY[
     date '2017-11-04',
     date '2017-11-05',
@@ -415,7 +407,57 @@ FROM unnest(ARRAY[
     date '2017-11-09'
     ]) AS time;
 
+SELECT time, time_bucket(INTERVAL '4 day', time::date, INTERVAL '2 day')
+FROM unnest(ARRAY[
+    date '2017-11-06',
+    date '2017-11-07',
+    date '2017-11-10',
+    date '2017-11-11'
+    ]) AS time;
 
+-- 2019-09-24 is a Monday.
+SELECT time, time_bucket(INTERVAL '1 week', time::date)
+FROM unnest(ARRAY[
+    date '2018-09-16',
+    date '2018-09-17',
+    date '2018-09-23',
+    date '2018-09-24'
+    ]) AS time;
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '2018-09-16',
+    timestamp without time zone '2018-09-17',
+    timestamp without time zone '2018-09-23',
+    timestamp without time zone '2018-09-24'
+    ]) AS time;
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp with time zone '2018-09-16',
+    timestamp with time zone '2018-09-17',
+    timestamp with time zone '2018-09-23',
+    timestamp with time zone '2018-09-24'
+    ]) AS time;
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp with time zone '-Infinity',
+    timestamp with time zone 'Infinity'
+    ]) AS time;
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '-Infinity',
+    timestamp without time zone 'Infinity'
+    ]) AS time;
+
+
+SELECT time, time_bucket(INTERVAL '1 week', time)
+FROM unnest(ARRAY[
+    timestamp without time zone '4714-11-24 01:01:01.0 BC',
+    timestamp without time zone '294276-12-31 23:59:59.9999'
+    ]) AS time;
 -------------------------------------
 --- Test time input functions --
 -------------------------------------