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,
3) to reduce the unnecessary work of rebasing and resolving
conflicts 4) to make the work easier to the reviewers

sql/CMakeLists.txt

@@ -37,6 +37,7 @@ 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 at
+-- your own risk.
+CREATE OR REPLACE FUNCTION timescaledb_experimental.time_bucket_ng(bucket_width INTERVAL, ts DATE) RETURNS DATE
+	AS '@MODULE_PATHNAME@', 'ts_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@', 'ts_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@', 'ts_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@', 'ts_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@', 'ts_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@', 'ts_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 +1,152 @@
+/*
+ * 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(ts_time_bucket_ng);
+TS_FUNCTION_INFO_V1(ts_time_bucket_ng_timestamp);
+TS_FUNCTION_INFO_V1(ts_time_bucket_ng_timestamptz);
+
+TSDLLEXPORT Datum
+ts_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(ts_time_bucket_ng,
+													 interval,
+													 DateADTGetDatum(ts_date),
+													 DateADTGetDatum(origin)));
+	}
+	else
+	{
+		result = DatumGetDateADT(
+			DirectFunctionCall2(ts_time_bucket_ng, interval, DateADTGetDatum(ts_date)));
+	}
+
+	return DirectFunctionCall1(date_timestamp, DateADTGetDatum(result));
+}
+
+TSDLLEXPORT Datum
+ts_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(ts_time_bucket_ng,
+													 interval,
+													 DateADTGetDatum(ts_date),
+													 DateADTGetDatum(origin)));
+	}
+	else
+	{
+		result = DatumGetDateADT(
+			DirectFunctionCall2(ts_time_bucket_ng, interval, DateADTGetDatum(ts_date)));
+	}
+
+	return DirectFunctionCall1(date_timestamptz, DateADTGetDatum(result));
+}
+
+TSDLLEXPORT Datum
+ts_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_INVALID_PARAMETER_VALUE),
+				 errmsg("interval must be either days and weeks, or months and years")));
+	}
+
+	if ((interval->month == 0) && (interval->day == 0))
+	{
+		/*
+		 * This will be fixed in future versions of ts_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_INVALID_PARAMETER_VALUE),
+				 errmsg("interval must be at least one day")));
+	}
+
+	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_INVALID_PARAMETER_VALUE),
+				 errmsg("origin must be the first day of the month")));
+	}
+
+	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_INVALID_PARAMETER_VALUE),
+					 errmsg("origin must be before the given date")));
+		}
+
+		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_INVALID_PARAMETER_VALUE),
+					 errmsg("origin must be before the given date")));
+		}
+
+		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 ts_time_bucket_ng(PG_FUNCTION_ARGS);
+extern TSDLLEXPORT Datum ts_time_bucket_ng_timestamp(PG_FUNCTION_ARGS);
+extern TSDLLEXPORT Datum ts_time_bucket_ng_timestamptz(PG_FUNCTION_ARGS);
+
+#endif /* TIMESCALEDB_DATE_TRUNC_H */