CURRENT_TIME

hi

i need to know the execution time of a part of my pl/pgsql code

so, i tried to use CURRENT_TIME :

t_time_d TIME;
t_time_f TIME;
t_diff TIME;

select CURRENT_TIME into t_time_d;

//the traitment

select CURRENT_TIME into t_time_f;
t_diff=t_time_f-t_time_d;
raise notice 'DEBUT : % | FIN : % | DIFF : % | POUR :
%',t_time_d,t_time_f,t_diff;

my function is recursive and the problem is that i always get the same
result for each iteration
t_time_d is set at the first iteration and doesn't change

thanks