modify sql functions

sql/set_artist_name.sql

@@ -1,14 +1,18 @@
-CREATE OR REPLACE PROCEDURE set_artist_name(in_url text) AS $$
+CREATE OR REPLACE FUNCTION public.set_artist_name(in_url text) RETURNS integer
+	LANGUAGE plpgsql STRICT
+	AS $$
 DECLARE
 	temp_artist_id integer;
 	temp_artist_name text;
-	temp_artist artist%ROWTYPE;
 BEGIN
 	temp_artist_name = get_artist_name(in_url);
 	temp_artist_name = convert_artist_name(temp_artist_name);
 
-	SELECT * INTO temp_artist FROM artist 
-	WHERE artist.name = temp_artist_name;
+	IF temp_artist_name IS NULL THEN
+		RETURN 1;
+	END IF;
+
+	PERFORM * FROM artist WHERE artist.name = temp_artist_name;
 
     IF NOT FOUND THEN
         INSERT INTO artist (name) VALUES (temp_artist_name);
@@ -19,5 +23,7 @@ BEGIN
 	
 	UPDATE artist_website SET artist_id = temp_artist_id 
 	WHERE url = in_url;
+
+	RETURN 0;
 END;
-$$ LANGUAGE plpgsql;
+$$;