dbforge add field "unique" to disallow duplicate inserts.

[eluser]Unknown[/eluser]
Using mysql it's pretty easy to specify a column as UNIQUE e.g. UNIQUE (column).

How can I do it with dbforge and not fallback to using raw db commands? Am using migration to setup the schema.

Code:

//EMAIL
           "email" => array(
                'type' => 'VARCHAR',
                'constraint' => 45,
                'null' => false
            ),

thanks,
James Tan