Cloudkit Fetch very slow - ios

Question

Running the below code to fetch data from Cloudkit, at the moment it is taking a long to populate a tableView, depending on how many results there are, but if there are over 15 results it takes 10 seconds plus. Are they any ways I can speed this up?
This is my fetch func:
func loadData() {
venues = [CKRecord]()
let location = locationManager.location
let radius = CLLocationDistance(500)
let sort = CKLocationSortDescriptor(key: "Location", relativeLocation: location!)
let predicate = NSPredicate(format: "distanceToLocation:fromLocation:(%K,%#) < %f", "Location", location!, radius)
let publicData = CKContainer.defaultContainer().publicCloudDatabase
let query = CKQuery(recordType: "Venues", predicate: predicate )
query.sortDescriptors = [sort]
publicData.performQuery(query, inZoneWithID: nil) { (results:[CKRecord]?, error:NSError?) in
if let venues = results {
self.venues = venues
dispatch_async(dispatch_get_main_queue(), {
self.tableView.reloadData()
self.refreshControl.endRefreshing()
self.tableView.hidden = false
})
}
}
}
This is my tableView func:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! NearMe2ViewCell
if venues.count == 0 {
return cell
}
let venue = venues[indexPath.row]
print(indexPath.row)
let venueLocation = venue["Location"] as? CLLocation
let venueTitle = (venue["Name"] as! String)
let venueImages = venue["VenuePhoto"] as! CKAsset
let userLocation = locationManager.location
let distanceBetween: CLLocationDistance = (venueLocation!.distanceFromLocation(userLocation!))
self.venueDistance = String(format: "%.f", distanceBetween)
cell.venueDistance?.text = venueDistance
cell.venueName.text = venueTitle
cell.venueImage?.image = UIImage(contentsOfFile: venueImages.fileURL.path!)
return cell
}

Answer 1

You should search for the record keys first, so a fetchOperation would include this directive.
fetchOperation.desiredKeys = ["record.recordID.recordName"]
That should be faster. Break your returned keys into the size you can display on the screen and go get them only. After you display them, go get the next batch in background thread, when you got that the next batch on background etc etc etc.
Should add perhaps, that fetching the asset should be done on a separate thread too if possible, updating the table as you pull in the assets by reloading the table repeatedly.
Here is method to search and return keys.
func zap(theUUID:String) {
var recordID2Zap: String!
let predicate = NSPredicate(format: "(theUUID = %#)",theUUID)
let query = CKQuery(recordType: "Blah", predicate: predicate)
let searchOperation = CKQueryOperation(query: query)
searchOperation.desiredKeys = ["record.recordID.recordName"]
searchOperation.recordFetchedBlock = { (record) in
recordID2Zap = record.recordID.recordName
}
if error != nil {
print("ting, busted",error!.localizedDescription)
} else {
print("ok zapping")
if recordID2Zap != nil {
self.privateDB.delete(withRecordID: CKRecordID(recordName: recordID2Zap), completionHandler: {recordID, error in
NSLog("OK or \(error)")
})
}
}
}
searchOperation.qualityOfService = .background
privateDB.add(searchOperation)
theApp.isNetworkActivityIndicatorVisible = true
}
}
As for your tableview, and images... use the completion in your icloud code to send a notification to the table view.
database.fetchRecordWithID(CKRecordID(recordName: recordId), completionHandler: {record, error in
let directDict = ["blah": "whatever"] as [String : String]
NotificationCenter.default.post(name: Notification.Name("blahDownloaded"), object: nil, userInfo: directDict)
}
And in the VC you register said notification.
NotificationCenter.default.addObserver(self, selector: #selector(blahDownloaded), name: Notification.Name("blahDownloaded"), object: nil)
func blahDownloaded(notification: NSNotification) {
if let userInfo = notification.userInfo as NSDictionary? as? [String: Any] {
//update you cell
//reload your table
}
Does that all make sense?

Answer 2

Your operation's qualityOfService is defaulting to .utility.
There is an important note in the documentation for CKOperation that states:
CKOperation objects have a default quality of service level of NSQualityOfServiceUtility (see qualityOfService). Operations at this level are considered discretionary, and are scheduled by the system for an optimal time based on battery level and other factors.
Because CKOperation inherits from NSOperation you can configure the qualityOfService property when your user is waiting on a request to finish. Here is some example code based off of yours above:
let queryOperation = CKQueryOperation(query: query)
queryOperation.recordFetchedBlock = ...
queryOperation.queryCompletionBlock = ...
queryOperation.qualityOfService = .userInteractive
publicData.add(queryOperation)
Notice that this example explicitly creates a CKQueryOperation instead of using the convenience API because it then gives you the flexibility to fully configure your operations before you enqueue them to be sent to the server.
In this case you can set the qualityOfService to .userInteractive because your user is actively waiting on the request to finish before they can use your app any further. Learn more about the possible values at https://developer.apple.com/library/content/documentation/Performance/Conceptual/EnergyGuide-iOS/PrioritizeWorkWithQoS.html