CloudKit Query Time - objective-c

Question

I've just started trialling CloudKit and am having some pretty slow query times. Here is some sample code I am using:
//CLOUDKIT
CKContainer *container = [CKContainer defaultContainer];
CKDatabase *privateDatabase = [container privateCloudDatabase];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"TRUEPREDICATE"];
CKQuery *query = [[CKQuery alloc] initWithRecordType:#"FlightLog" predicate:predicate];
[privateDatabase performQuery:query inZoneWithID:nil completionHandler:^(NSArray *results, NSError *error) {
//SUCCESS
if (!error)
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"SUCCESS" message:#"IT WORKED" delegate:self cancelButtonTitle:#"dismiss" otherButtonTitles:nil];
[alert show];
NSLog(#"%#", #"fetchFlights success!");
NSLog(#"%#", self.fetchedRecords);
self.fetchedRecords = results;
[self.tableView reloadData];
}
//ERROR
else
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"error" message:error.localizedDescription delegate:self cancelButtonTitle:#"dismiss" otherButtonTitles:nil];
[alert show];
NSLog(#"%#", error);
}
}];
I get the private database, and query for all records. There is just four simple ones I added in the dashboard.
Upon calling this code, I can see from my console log that the success message gets called almost immediately, with a null results array. Then moments later, the results are returned, as seen in the log. However, the alert view isn't shown and results displayed in my table for about 3-4 more seconds.
What's going on?

Answer 1

This is resolved. As Edwin mentions, I didn't know that the callback is on a background thread. So when I call [self.tableView reloadData] in the completion block, it is also running on the background thread.
By putting it back on the main thread, the table view reloads within about a second. Vs taking about 4-5 seconds if running on the same thread as the callback.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
});
Let me know if I have misunderstood, but I think that's what has happened.