question: public void AddKey ( Key key ) { keys . add ( key ) ; if ( key . getType ( ) == Key . Primary ) { primaryKey = key ; purge ( key . getColumns ( ) , nonKeyColumns ) ; } else if ( key . getType ( ) == Key . Unique ) { uniqueKeys . add ( key ) ; } }
target:  Adds a key definition to the table. This method maintains non-key columns automatically, as well as unique keys.