time_bucket_ng() (next generation) experimental function is an updated
version of the original
time_bucket() function. While
time_bucket works only with small units of time,
supports years and months in addition to small units of time.
|Buckets by seconds, minutes, hours, days and weeks||YES||YES|
|Buckets by months and years||NO||YES|
time_bucket_ng() functions are similar, but not completely compatible. There are two main differences.
time_bucket_ng() doesn't work with timestamps prior to
Secondly, the default
origin values differ.
time_bucket() uses an origin
date of 3 Jan 2000, because that date is a Monday. This works better with
time_bucket_ng() uses an origin date of 1 Jan 2000, because
it is the first day of the month and the year. This works better with monthly
or annual aggregates.
|INTERVAL||A PostgreSQL time interval for how long each bucket is|
|DATE, TIMESTAMP or TIMESTAMPTZ||The timestamp to bucket|
|Should be the same as ||Buckets are aligned relative to this timestamp|
|TEXT||The name of the timezone. The argument can be specified only if the type of |
For backward compatibility with
timezone argument is
optional. Note that if you call the TIMESTAMPTZ-version of the function
timezone argument, the timezone defaults to the session's
timezone and so the function can't be used with continuous aggregates.
The function returns the bucket's start time. The return value type is the
In this example,
time_bucket_ng() is used to create bucket data in three month
SELECT timescaledb_experimental.time_bucket_ng('3 month', date '2021-08-01'); time_bucket_ng ---------------- 2021-07-01 (1 row)
This example uses
time_bucket_ng() to bucket data in one year intervals:
SELECT timescaledb_experimental.time_bucket_ng('1 year', date '2021-08-01'); time_bucket_ng ---------------- 2021-01-01 (1 row)
To split time into buckets,
time_bucket_ng() uses a starting point in time
origin. The default origin is
time_bucket_ng cannot use
timestamps earlier than
SELECT timescaledb_experimental.time_bucket_ng('100 years', timestamp '1988-05-08'); ERROR: origin must be before the given date
Going back in time from
origin isn't usually possible, especially when you
consider timezones and daylight savings time (DST). Note also that there is no
reasonable way to split time in variable-sized buckets (such as months) from an
origin defaults to the first day of the month.
To bypass named limitations, you can override the default
-- working with timestamps before 2000-01-01 SELECT timescaledb_experimental.time_bucket_ng('100 years', timestamp '1988-05-08', origin => '1900-01-01'); time_bucket_ng --------------------- 1900-01-01 00:00:00 -- unlike the default origin, which is Saturday, 2000-01-03 is Monday SELECT timescaledb_experimental.time_bucket_ng('1 week', timestamp '2021-08-26', origin => '2000-01-03'); time_bucket_ng --------------------- 2021-08-23 00:00:00
This example shows how
time_bucket_ng() is used to bucket data
by months in a specified timezone:
-- note that timestamptz is displayed differently depending on the session parameters SET TIME ZONE 'Europe/Moscow'; SET SELECT timescaledb_experimental.time_bucket_ng('1 month', timestamptz '2001-02-03 12:34:56 MSK', timezone => 'Europe/Moscow'); time_bucket_ng ------------------------ 2001-02-01 00:00:00+03
You can use
time_bucket_ng() with continuous aggregates. This example tracks
the temperature in Moscow over seven day intervals:
CREATE TABLE conditions( day DATE NOT NULL, city text NOT NULL, temperature INT NOT NULL); SELECT create_hypertable( 'conditions', 'day', chunk_time_interval => INTERVAL '1 day' ); INSERT INTO conditions (day, city, temperature) VALUES ('2021-06-14', 'Moscow', 26), ('2021-06-15', 'Moscow', 22), ('2021-06-16', 'Moscow', 24), ('2021-06-17', 'Moscow', 24), ('2021-06-18', 'Moscow', 27), ('2021-06-19', 'Moscow', 28), ('2021-06-20', 'Moscow', 30), ('2021-06-21', 'Moscow', 31), ('2021-06-22', 'Moscow', 34), ('2021-06-23', 'Moscow', 34), ('2021-06-24', 'Moscow', 34), ('2021-06-25', 'Moscow', 32), ('2021-06-26', 'Moscow', 32), ('2021-06-27', 'Moscow', 31); CREATE MATERIALIZED VIEW conditions_summary_weekly WITH (timescaledb.continuous) AS SELECT city, timescaledb_experimental.time_bucket_ng('7 days', day) AS bucket, MIN(temperature), MAX(temperature) FROM conditions GROUP BY city, bucket; SELECT to_char(bucket, 'YYYY-MM-DD'), city, min, max FROM conditions_summary_weekly ORDER BY bucket; to_char | city | min | max ------------+--------+-----+----- 2021-06-12 | Moscow | 22 | 27 2021-06-19 | Moscow | 28 | 34 2021-06-26 | Moscow | 31 | 32 (3 rows)
For more information, see the continuous aggregates documentation.
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