MSSQL -> Postgres stored procedure migration/plpgsql help?

I'm migrated a webapp from MSSQL to Postgresql and I'm having some problems with the store procedure. This is what I have so far, but it doesn't seem to be working.

What I need to do

1.) Get the visitor_id
I want to check to see if the current cookie is associated with a visitor_id, if the visitor_id is not found, then add it and put the visitor_id into a variable, if it is found then store it in the visitor_id variable.

2.) Get the session_id
Next I need to check to see if the current session has been stored in the db, if it has been return the session_id, if not, it should be added and a session_id should be returned.

3.) Save the page view
Insert the pageview record.

---------------------

CREATE FUNCTION log_page_view(int,varchar,varchar,varchar,varchar) RETURNS INTEGER AS '
DECLARE
local_account_id ALIAS FOR $1;
local_cookie_id ALIAS FOR $2;
local_user_agent ALIAS FOR $3;
local_client_ip ALIAS FOR $4;
local_page_url ALIAS FOR $5;
local_visitor_id int := 0;
local_session_id int := 0;
BEGIN

SELECT INTO local_visitor_id visitor_id FROM web_visitors WHERE cookie_id = local_cookie_id;
IF NOT FOUND THEN
INSERT INTO web_visitors(account_id) VALUES(1);
SELECT INTO local_visitor_id max(visitor_id) FROM web_visitors;
END IF;

SELECT INTO local_session_id visitor_id FROM web_visitor_sessions WHERE visitor_id = local_cookie_id AND cookie_id=local_cookie_id;
IF NOT FOUND THEN
INSERT INTO web_visitor_sessions(visitor_id,cookie_id,client_ip,user_agent) VALUES(local_visitor_id,local_cookie_id,local_client_ip,local_user_agent);
SELECT INTO local_session_id session_id FROM max(session_id) FROM web_visitor_sessions;
END IF;

INSERT INTO web_pageviews(session_id,page_url) VALUES(local_session_id,local_page_url);

RETURN local_visitor_id;
END;
' LANGUAGE 'plpgsql';