Question

Is it possible to rewrite the following plpgsql function as a sql function?
I’m using it to aggregate my data by most recent timestamp, but wish to deploy on heroku which doesn’t support plpgsql.
I could totally rewrite my original query that uses this function, but I’d like to keep the flexibility for being able to drop in other aggregate functions.

CREATE OR REPLACE FUNCTION recent_accum(anyelement, anyelement)
  RETURNS anyelement AS $$
     BEGIN
        IF $1.tstamp IS NULL and $2.tstamp IS NOT NULL
           THEN RETURN $2;
        ELSEIF $1.tstamp IS NOT NULL and $2.tstamp IS NULL
           THEN RETURN $1;
        ELSEIF $2.tstamp > $1.tstamp
           THEN RETURN $2;
        ELSE RETURN $1;
        END IF;
     END;
  $$ LANGUAGE plpgsql;

Answer 1

Does it work to rewrite the IF/ELSEIF chain using CASE?

CASE
WHEN $1.tstamp IS NULL AND $2.tstamp IS NOT NULL
     THEN $2
-- ...
ELSE $1
END