DB_Forge and Multiple Column Non-primary Keys

[eluser]Unknown[/eluser]
According to the documentation (http://ellislab.com/codeigniter/user-gui...ml#add_key), passing an array as the first parameter of DB_Forge::add_key() causes it to make a multi-column key.

However, after testing it thoroughly, I've come to the conclusion that the documentation is incorrect -- add_key() creates multiple single-column keys when passed an array and no second argument. Taking a look at the source code (/system/database/DB_Forge.php:104) and following the path of the object's $keys variable, it is clear that the method does not perform as the documentation suggests.