How to update all records as quickly as possible? - ios

Question

I need to update all the records with the same value. And I don't want to do it with iteration over objects since that takes about 2 seconds for over 2000 objects. Basically I have all users locally and I receive the users id's from the server. I now want to set property 'requested' to false except for the users return from the server-
How it is done now (which is totally wrong!):
Iterating thru all users (about 2000 of them) and correcting their requested value.
NSFetchRequest * allUsers = [[NSFetchRequest alloc] init];
[allUsers setEntity:[NSEntityDescription entityForName:#"User" inManagedObjectContext:context]];
NSArray *users = [context executeFetchRequest:allUsers error:&error];
NSArray *userIDs = [JSON objectForKey:#"users_ids"];
for (User *user in users) {
if ([userIDs containsObject:user.userID]) {
user.requested = [NSNumber numberWithBool:YES];
} else {
user.requested = [NSNumber numberWithBool:NO];
}
user.requested = [NSNumber numberWithBool:NO];
}
[context save:nil];
My idea how to do it:
Set requested=false for every object with a sql-like one statement. Going thru id's returned by the server (20 on average) and setting requested=true for those.
// UPDATE users SET requested = false WHERE 1=1
NSArray *userIDs = [JSON objectForKey:#"users_ids"];
for (int i = 0; i < [userIDs count]; i++) {
User *user = [User userWithServerID:[userIDs[i] integerValue] usingManagedObjectContext:context];
user.requested = [NSNumber numberWithBool:YES];
}
[context save:nil];
So how could I update all the records with one "query" ? Or does anyone have any better idea how to implement this (more performance efficient way of doing the iteration perhaps) ?
Putting this in the background thread is a solution (perhaps), but I would still like to optimise it first before putting it in the background thread.
Thank you!

Answer 1

You would still have to fetch all the objects but you can do it all in one line.
[[fetchedResultsController fetchedObjects] makeObjectsPerformSelector:#selector(setYourValue:) withObject:[NSNumber numberWithBool:YES]];
Or just cycle the array
NSArray *objects = [context executeFetchRequest:allRequest error:&error];
[objects setValue:[NSNumber numberWithBool:YES] forKey:#"user_ids"];
//now save your changes back.
[context save:&error];