Sphinx and natural sorting

CREATE OR REPLACE FUNCTION string_ordinal(str character varying) RETURNS double precision AS $BODY$ DECLARE _norm VARCHAR; _ln SMALLINT; _max_ln SMALLINT; i SMALLINT; o DOUBLE PRECISION; CHAR sym; code SMALLINT; norm_code SMALLINT; BEGIN _max_ln := 100; _norm := regexp_replace(lower(str), '[^A-Za-z0-9a-za-Eee]', ", 'g'); _ln = length(_norm); IF _ln < _max_ln THEN _norm = rpad(_norm, _max_ln, '.'); _ln = length(_norm); END IF; o := 0.0; FOR i IN 1.._ln LOOP sym := SUBSTRING(_norm FROM i FOR 1)::CHAR; code := ascii(sym); norm_code := 0; IF code = 46 THEN norm_code := 1; END IF; IF code >= 48 AND code <= 57 THEN -- 0-9 norm_code := code - 46; END IF; IF code >= 97 AND code <= 122 THEN -- a-z norm_code := code - (96 - 10); END IF; IF code >= 1072 AND code <= 1105 THEN-and-I + e IF code = 1105 THEN-ie the code is greater than I, it's bad code := 1078; ELSIF code > 1077 THEN code := code + 1; END IF; norm_code := code - (1071 - 36); END IF; o := o + norm_code * power(68, (_ln - i)); END LOOP; RETURN o; END; $BODY$ LANGUAGE plpgsql VOLATILE COST 100;