Интервал выполнения и sleep

do $$
DECLARE
t NUMERIC;
BEGIN
select EXTRACT(EPOCH FROM timeofday()::TIMESTAMP) into t;
raise notice 't=%',t;

perform pg_sleep(2);

select EXTRACT(EPOCH FROM timeofday()::TIMESTAMP) into t;
raise notice 't=%',t;


select EXTRACT(EPOCH FROM timeofday()::TIMESTAMP) into t;
raise notice 't=%',t;

end $$

----------------- 

00000: t=1512065827.6849

00000: t=1512065829.6977

00000: t=1512065829.69793