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 ;

Note that some mysql-5.0 versions have a bug that crashes the database when running this script. It has to do with the identical name max_error_count and @@max_error_count.

Can be circumvented by renaming max_error_count to e.g. _max_error_count, lines 7 and 10

This has been proved very useful! +1

Very useful thanks!