Returns a probability distribution of words

gistfile1.sql

CREATE OR REPLACE FUNCTION somefuncname() RETURNS int LANGUAGE plpgsql AS $$
DECLARE
  tmp int;
BEGIN
  CREATE TEMP TABLE res AS SELECT id, SUM(count) OVER (ORDER BY id DESC) AS cum_sum FROM chains WHERE wid=## GROUP BY id ORDER BY cum_sum DESC;
  tmp := FLOOR(random()*( SELECT max(cum_sum) FROM res LIMIT 1 ));
  RETURN (SELECT cum_sum FROM res WHERE cum_sum > tmp ORDER BY cum_sum ASC LIMIT 1 );
END