debugging functions

Hi,

I am aware of the edb-debugger that one can use with pgadmin for
debugging functions.  However, I am looking for a solution that doesn't
involve such additions to the server.  I'm using a function in a SELECT
query, but it's failing for some rows in a very large table.  By using
LIMIT and OFFSET I see that it runs fine for some parts of the table.
Is there some way to print the rows where it fails?  For now, I've
simply modified the function to return a value that I can use in the
SELECT query to filtering, but I'm wondering whether there's a parameter
or setting that would accomplish the same thing without modifying the
function.

Thanks,

--
Seb