MySQL has fulltext index search ability for text field, but it is word
based index: it cannot be used for no word delimiter language like
Japanese or Chinese.  It also can't search characters in the middle of
a word (e.g. searching 'in' will not match word 'ping').

Starting from MySQL 5.1, MySQL supports a plugin that allows to change
server components (fulltext search parser) without restarting and/or
recompiling the server.

This n-gram parser uses this plugin interface to implement a simple
n-gram (bi-gram) fulltext index parser which can be used for languages
without word delimiters.