How to round to nearest X minutes with PL/pgSQL?

Question

How I can round to nearest X minutes?

Here\'s my attempt:

DECLARE
  _stamp ALIAS FOR $1; -- timestamp
  _nearest ALIAS FOR $2; -- minutes (integer)
         


        

Answer 1

You can do it as a simple SQL statement, substitute CURRENT_TIMESTAMP with your TIMESTAMP value.

SELECT date_trunc('minute', CURRENT_TIMESTAMP::timestamp without time zone)
    + (
    CASE WHEN extract(second from CURRENT_TIMESTAMP ) >= 30
        THEN 1::text
        ELSE 0::text
    END
    || ' minute'

    )::interval ;

An optimization, would be adding 30 seconds and then just doing date_trunc(), I knew this before but special thanks irc://irc.freenode.net/#postgresql's StuckMojo

SELECT date_trunc(
    'minute'
    , CURRENT_TIMESTAMP::timestamp without time zone
      + '30 seconds'::interval
);

update @stephen, sure it does -- even though technically speaking that isn't what the question called for.

CREATE OR REPLACE FUNCTION round_trunc ( in text, in timestamp ) RETURNS timestamp without time zone  AS $$
  SELECT pg_catalog.date_trunc(
      $1
      , $2::timestamp without time zone
        + ('0.5 ' || $1 )::interval
  )
$$ LANGUAGE sql VOLATILE;

Oh wait, I see what he is asking for, he wants to round to the nearest abstract sub-unit of time. Like a quarter hour, I'm way off here.