maybe_utf8_decode: MySQL function to recover doubly UTF-8 encoded text

maybe_utf8_decode.sql

DELIMITER $$

CREATE FUNCTION maybe_utf8_decode(str text charset utf8) 
RETURNS text CHARSET utf8 DETERMINISTIC
BEGIN
declare str_converted text charset utf8;
declare max_error_count int default @@max_error_count;
set @@max_error_count = 0;
set str_converted = convert(binary convert(str using latin1) using utf8);
set @@max_error_count = max_error_count;
if @@warning_count > 0 then
    return str;
else
    return str_converted;
end if;
END$$

DELIMITER ;

Very useful thanks!