Introduce experimental time_bucket_ng() function

This patch adds time_bucket_ng() function to the experimental
schema. The "ng" part stands for "next generation". Unlike
current time_bucket() implementation the _ng version will support
months, years and timezones.

Current implementation doesn't claim to be complete. For instance,
it doesn't support timezones yet. The reasons to commit it in it's
current state are 1) to shorten the feedback loop 2) to start
experimenting with monthly buckets are soon as possible and
3) to reduce the unnecessary work of rebasing and resolving
conflicts.

sql/CMakeLists.txt

@@ -40,6 +40,7 @@ set(SOURCE_FILES
   ddl_triggers.sql
   bookend.sql
   time_bucket.sql
+  time_bucket_ng.sql
   version.sql
   size_utils.sql
   histogram.sql

sql/time_bucket_ng.sql

@@ -0,0 +1,29 @@
+-- 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.
+
+-- time_bucket_ng() is an _experimental_ new version of time_bucket().
+--
+-- Unlike time_bucket(), time_bucket_ng() supports variable-sized buckets,
+-- such as months and years, and also timezones. Note that the behavior
+-- and the interface of this function are subjects to change. There could
+-- be bugs, and the implementation doesn't claim to be complete. Use on
+-- your own risk.
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts DATE) RETURNS DATE
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng' LANGUAGE C STABLE PARALLEL SAFE STRICT;
+
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts DATE, origin DATE) RETURNS DATE
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng' LANGUAGE C STABLE PARALLEL SAFE STRICT;
+
+-- utility functions
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts TIMESTAMP) RETURNS TIMESTAMP
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng_timestamp' LANGUAGE C STABLE PARALLEL SAFE STRICT;
+
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts TIMESTAMP, origin TIMESTAMP) RETURNS TIMESTAMP
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng_timestamp' LANGUAGE C STABLE PARALLEL SAFE STRICT;
+
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts TIMESTAMPTZ) RETURNS TIMESTAMPTZ
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng_timestamptz' LANGUAGE C STABLE PARALLEL SAFE STRICT;
+
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts TIMESTAMPTZ, origin TIMESTAMPTZ) RETURNS TIMESTAMPTZ
+	AS '@MODULE_PATHNAME@', 'time_bucket_ng_timestamptz' LANGUAGE C STABLE PARALLEL SAFE STRICT;

src/CMakeLists.txt

@@ -48,6 +48,7 @@ set(SOURCES
   subspace_store.c
   tablespace.c
   time_bucket.c
+  time_bucket_ng.c
   time_utils.c
   custom_type_cache.c
   trigger.c

src/time_bucket_ng.c

@@ -0,0 +1,154 @@
+/*
+ * 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.
+ */
+#include <postgres.h>
+#include <utils/date.h>
+#include <utils/datetime.h>
+#include <utils/fmgrprotos.h>
+
+#include "time_bucket_ng.h"
+
+TS_FUNCTION_INFO_V1(time_bucket_ng);
+TS_FUNCTION_INFO_V1(time_bucket_ng_timestamp);
+TS_FUNCTION_INFO_V1(time_bucket_ng_timestamptz);
+
+TSDLLEXPORT Datum
+time_bucket_ng_timestamp(PG_FUNCTION_ARGS)
+{
+	DateADT result;
+	Datum interval = PG_GETARG_DATUM(0);
+	DateADT ts_date = DatumGetDateADT(DirectFunctionCall1(timestamp_date, PG_GETARG_DATUM(1)));
+
+	if (PG_NARGS() > 2)
+	{
+		DateADT origin = DatumGetDateADT(DirectFunctionCall1(timestamp_date, PG_GETARG_DATUM(2)));
+		result = DatumGetDateADT(DirectFunctionCall3(time_bucket_ng,
+													 interval,
+													 DateADTGetDatum(ts_date),
+													 DateADTGetDatum(origin)));
+	}
+	else
+	{
+		result = DatumGetDateADT(
+			DirectFunctionCall2(time_bucket_ng, interval, DateADTGetDatum(ts_date)));
+	}
+
+	return DirectFunctionCall1(date_timestamp, DateADTGetDatum(result));
+}
+
+TSDLLEXPORT Datum
+time_bucket_ng_timestamptz(PG_FUNCTION_ARGS)
+{
+	DateADT result;
+	Datum interval = PG_GETARG_DATUM(0);
+	DateADT ts_date = DatumGetDateADT(DirectFunctionCall1(timestamptz_date, PG_GETARG_DATUM(1)));
+
+	if (PG_NARGS() > 2)
+	{
+		DateADT origin = DatumGetDateADT(DirectFunctionCall1(timestamptz_date, PG_GETARG_DATUM(2)));
+		result = DatumGetDateADT(DirectFunctionCall3(time_bucket_ng,
+													 interval,
+													 DateADTGetDatum(ts_date),
+													 DateADTGetDatum(origin)));
+	}
+	else
+	{
+		result = DatumGetDateADT(
+			DirectFunctionCall2(time_bucket_ng, interval, DateADTGetDatum(ts_date)));
+	}
+
+	return DirectFunctionCall1(date_timestamptz, DateADTGetDatum(result));
+}
+
+TSDLLEXPORT Datum
+time_bucket_ng(PG_FUNCTION_ARGS)
+{
+	Interval *interval = PG_GETARG_INTERVAL_P(0);
+	DateADT date = PG_GETARG_DATEADT(1);
+	DateADT origin_date = 0; // 2000-01-01
+	int origin_year = 2000, origin_month = 1, origin_day = 1;
+	int year, month, day;
+	int delta, bucket_number;
+
+	if ((interval->time != 0) || ((interval->month != 0) && (interval->day != 0)))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("unsupported interval: use either days and weeks, or months and years")));
+	}
+
+	if ((interval->month == 0) && (interval->day == 0))
+	{
+		/*
+		 * This will be fixed in furhter versions of time_bucket_ng().
+		 * The reason why it's not yet implemented is that we want to start
+		 * experimenting with variable-sized buckets as soon as possible.
+		 * We know that fixed-sized buckets work OK and adding corresponding
+		 * logic will be trivial.
+		 */
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("unsupported interval: at least one day expected")));
+	}
+
+	if (PG_NARGS() > 2)
+	{
+		origin_date = PG_GETARG_DATUM(2);
+		j2date(origin_date + POSTGRES_EPOCH_JDATE, &origin_year, &origin_month, &origin_day);
+	}
+
+	if ((origin_day != 1) && (interval->month != 0))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("Invalid 'origin' day, 1st day of the month expected")));
+	}
+
+	if (DATE_NOT_FINITE(date))
+		PG_RETURN_DATEADT(date);
+
+	if (interval->month != 0)
+	{
+		/* Handle months and years */
+
+		j2date(date + POSTGRES_EPOCH_JDATE, &year, &month, &day);
+
+		if ((year < origin_year) || ((year == origin_year) && (month < origin_month)))
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("date is before origin, please choose an origin that is before all "
+							"dates")));
+		}
+
+		delta = (year * 12 + month) - (origin_year * 12 + origin_month);
+		bucket_number = delta / interval->month;
+		year = origin_year + (bucket_number * interval->month) / 12;
+		month =
+			(((origin_year * 12 + (origin_month - 1)) + (bucket_number * interval->month)) % 12) +
+			1;
+		day = 1;
+
+		date = date2j(year, month, day) - POSTGRES_EPOCH_JDATE;
+	}
+	else
+	{
+		/* Handle days and weeks */
+
+		if (date < origin_date)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("date is before origin, please choose an origin that is before all "
+							"dates")));
+		}
+
+		delta = date - origin_date;
+		bucket_number = delta / interval->day;
+		date = bucket_number * interval->day;
+	}
+
+	PG_RETURN_DATEADT(date);
+}

src/time_bucket_ng.h

@@ -0,0 +1,18 @@
+/*
+ * 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.
+ */
+#ifndef TIMESCALEDB_DATE_TRUNC_H
+#define TIMESCALEDB_DATE_TRUNC_H
+
+#include <postgres.h>
+#include <fmgr.h>
+
+#include "export.h"
+
+extern TSDLLEXPORT Datum time_bucket_ng(PG_FUNCTION_ARGS);
+extern TSDLLEXPORT Datum time_bucket_ng_timestamp(PG_FUNCTION_ARGS);
+extern TSDLLEXPORT Datum time_bucket_ng_timestamptz(PG_FUNCTION_ARGS);
+
+#endif /* TIMESCALEDB_DATE_TRUNC_H */