Fetching large number of data from CoreData using two NSFetchedResultsController

Question

I am trying to fetch 10000records from CoreData in a UITableView using NSFetchedResultsController and trying to make it as fast as possible (since the request has a sort descriptor it takes longer to fetch this amount of data).

I am trying to fetch 100records from CoreData with the first and main NSFetchedResultsController(used in the delegate methods of the table), that is displayed on the table while in another queue I started in viewDidAppear another fetch for all 10000records on an auxiliarFRC. After the fetch in the AuxFRC ends, I assign to the main FRC the AuxFRC so all the records get transfered and I reload the table.

My problem is that the UITableView gets stuck at the first loaded rows till the AuxFRC ends the fetch even if I dispatch the performFetch, and I can not understand why this happens, or if this way is wrong what other way can be used to fetch 10000records and stay up to date if the data changes?

Answer 1

I guess the problem was the NSManagedObjectContext - that is not thread safe and I used the same one for both the fetches. I created a copy of the original one and changed the AuxFRC on the second context. This solved everything.