Debugging postgresql functions

in psql, i do the
set client_min_messages TO debug;

and then in the function you can do
raise debug 'foo message: %', _a value;
where % are replaced by the _a_value, variable, etc?

the raise debug is only shown if client_min_messages is debug
so you can leave them in there after, and turn on debug mode later
then
when you create
the function
to test i sometimes do
begin transaction;
select function();
and then when it fails, or after i poke at results,
rollback;
well, handy for some kinds of testing