As documented under Fine-Tuning MySQL Full-Text Search:
The minimum and maximum lengths of words to be indexed are defined by the
InnoDBsearch indexes, and
MyISAMones. After changing any of these options, rebuild your
FULLTEXTindexes for the change to take effect. For example, to make two-character words searchable, you could put the following lines in an option file:[mysqld] innodb_ft_min_token_size=2 ft_min_word_len=2
Then restart the server and rebuild your
MyISAMtables, note particularly the remarks regarding myisamchk in the instructions following this list.