I have a table with four related ones. I made a view combining those tables in MySQL and created a model based on the view, and used it in a form with CJuiAutoComplete widget. The performance is awful.
first you should answer the question if you really need such query in autocomplete (there will be only one value displayed in most cases). Then you should check if the query used to create view is optimal - run explain on db console and check if it needs indexes and how it utilize them.