\timing on

create table if not exists random_tbl (random bigint);

do $$
begin
for i in 1..1000000 loop
TRUNCATE random_tbl;

INSERT INTO RANDOM_TBL (random)
  SELECT count(*) AS random
  FROM onek WHERE random() < 1.0/10;

-- select again, the count should be different
INSERT INTO RANDOM_TBL (random)
  SELECT count(*)
  FROM onek WHERE random() < 1.0/10;

-- select again, the count should be different
INSERT INTO RANDOM_TBL (random)
  SELECT count(*)
  FROM onek WHERE random() < 1.0/10;

-- select again, the count should be different
INSERT INTO RANDOM_TBL (random)
  SELECT count(*)
  FROM onek WHERE random() < 1.0/10;

-- now test that they are different counts
if (select true FROM RANDOM_TBL
  GROUP BY random HAVING count(random) > 3) then
raise notice 'duplicates at iteration %', i;
exit;
end if;

-- approximately check expected distribution
if (select true FROM RANDOM_TBL
  HAVING AVG(random) NOT BETWEEN 80 AND 120) then
raise notice 'range at iteration %', i;
exit;
end if;

end loop;
end $$;