UIDocumentPicker cache

This is the code I'm using ...

func importDatabase(view: UIViewController!, sender: AnyObject, activityIndicator: UIActivityIndicatorView) {
        self.view = view
        self.activityIndicator = activityIndicator
        let importMenu = UIDocumentMenuViewController(documentTypes: ["com.michaeltissington.uti.awdb"], inMode: .Import)
        importMenu.delegate = self
        importMenu.popoverPresentationController?.barButtonItem = sender as? UIBarButtonItem
        importMenu.popoverPresentationController?.sourceView = view.view
        view.presentViewController(importMenu, animated: true, completion: nil)
    }
    
    func documentMenuWasCancelled(documentMenu: UIDocumentMenuViewController) {
        documentMenu.dismissViewControllerAnimated(true, completion: nil)
        activityIndicator.stopAnimating()
    }
    
    func documentMenu(documentMenu: UIDocumentMenuViewController, didPickDocumentPicker documentPicker: UIDocumentPickerViewController) {
        documentPicker.delegate = self
        activityIndicator.startAnimating()
        view.presentViewController(documentPicker, animated: true, completion: nil)
    }
    
    func documentPickerWasCancelled(controller: UIDocumentPickerViewController) {
        activityIndicator.stopAnimating()
    }
    
    func documentPicker(controller: UIDocumentPickerViewController, didPickDocumentAtURL url: NSURL) {
        mergeDatabase(url)
        activityIndicator.stopAnimating()
        let fileManager = NSFileManager.defaultManager()
        try! fileManager.removeItemAtURL(url)
    }