postgresql date_trunc to arbitrary precision? - postgresql

Question

postgresql has date_trunc that can truncate the time stamp value to a specific unit, like hour or minute. I want to know if there's any build-in function that would allow me to truncate to 10 minutes?
I know one trick is to convert the time stamp to epoch, do some math, then convert back. But I don't like it.

Answer 1

There is no function you want, but as said in postgresql wiki you can define function for youself:
CREATE OR REPLACE FUNCTION round_time_10m(TIMESTAMP WITH TIME ZONE)
RETURNS TIMESTAMP WITH TIME ZONE AS $$
SELECT date_trunc('hour', $1) + INTERVAL '10 min' * ROUND(date_part('minute', $1) / 10.0)
$$ LANGUAGE SQL;
Generally rounding up to $2 minutes:
CREATE OR REPLACE FUNCTION round_time_nm(TIMESTAMP WITH TIME ZONE, INTEGER)
RETURNS TIMESTAMP WITH TIME ZONE AS $$
SELECT date_trunc('hour', $1) + ($2 || ' min')::INTERVAL * ROUND(date_part('minute', $1) / $2)
$$ LANGUAGE SQL;

Answer 2

here's an improved version of date_trunc
create cast (bigint as timestamptz) WITHOUT FUNCTION;
create cast (timestamptz as bigint) WITHOUT FUNCTION;
CREATE OR REPLACE FUNCTION date_trunc_by_interval( interval, timestamptz )
RETURNS timestamptz
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT
AS $$
select
case when $2::bigint >= 0::bigint then
$2::bigint - $2::bigint % (extract (epoch from $1)*1000000 ) ::bigint
else
$2::bigint - $2::bigint % (extract (epoch from $1)*1000000 ) ::bigint
- (extract (epoch from $1)*1000000 ) ::bigint
end ::timestamptz
$$;
this allows rounding to any fixed-length interval eg: '864 seconds' (divinding days into 100 parts) or '14 days' dividing the calendar into fortnights. the basis is '2000-01-01 00:00:00.0 +00' which is the epoch used to compute postgres
timestamp values.
it works by coercing the timestamptz value and the interval into bigints and doing integer arithmetic on them then coercing them back to timestamps
negative inputs need special handling (the case statement) as % causes rounding towards zero.

Answer 3

Postgres 14 date_bin.
Example use
SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01');
Result: 2020-02-11 15:30:00
The timescaleDb extension has a time_bucket function that supports day, minutes and lower intervals.
Note: it does currently not support months, years: see #414