Functions in MOnetdb

Hi! We are trying to create a couple of functions in Monet. Every function we create has a terrible bad performance. Can someone help me to find out what Im doing wrong ? Here is the function CREATE FUNCTION sb_glob.camelcase(input VARCHAR(500)) RETURNS VARCHAR(500) begin DECLARE len INT; DECLARE i INT; SET len = CHAR_LENGTH(input); SET input = LOWER(input); SET i = 0; WHILE (i < len) DO SET input = CASE WHEN ((SUBSTR(input,i,1) = ' ' OR SUBSTR(input,i,1) = '-' OR i = 0) AND (i < len)) THEN (LEFT(input,i) || UPPER(SUBSTR(input,i + 1,1)) || RIGHT(input,len - i - 1)) ELSE input END; SET i = i + 1; END WHILE; RETURN input; END Thks in advance!