Dojo ComboBox / Filtering Select Component可以加载的最大JSON数据大小是多少？

I'm developing a form using the Zend Framework and utilising dojo. One part of the form is gathering a users contact details and address. The issue I am hitting is using the FilteringSelect or ComboBox dojo component to select the city/town. I have in my database a list of 40K+ town/city names.I'm developing a form using the Zend Framework