On Fri, 9 Jul 2004, Dmitry Karasik wrote:
> Can anyone explain what may be the reason to the drastic difference
> in the execution speed of the same SQL statement, executed from the
> command line and from inside the stored procedure? Or, which is
> more important, how to fight this?
Those aren't the same statements precisely. In one case there's a given
anchored constant which can be used for purposes of planning and for
converting to an index condition. In the other, it's a variable, and
there's no way to know that you will not pass '%foo' or some other
non-anchored string.
If you want to replan inside the function using the actual passed value,
you can use some EXECUTE variant (probably FOR ... IN EXECUTE since you
want a value out).
Something like the untested:
CREATE OR REPLACE FUNCTION
f_test(TEXT)
RETURNS integer AS '
DECLARE
p_from ALIAS FOR $1;
c INTEGER;
r record;
BEGIN
FOR r IN EXECUTE ''select count(id) as c FROM queues WHERE
hostname LIKE '' || quote_literal(p_from) LOOP
RETURN r.c;
END LOOP;
RETURN NULL;
END;
' LANGUAGE 'plpgsql';
