Question

i have big pool of core date objects (around 10000) and there is too long time doing code according profile:
NSDate *maxExternalChangedDate = [codes valueForKeyPath:@”@max.externalChangedDate”];
is community know better way to found it?

NSString *rateSheetID = [rateSheetAndPrefix valueForKey:@"rateSheetID"];
NSFetchRequest *requestCodesForSale = [[NSFetchRequest alloc] init];
[requestCodesForSale setEntity:[NSEntityDescription entityForName:@"CodesvsDestinationsList"
                                           inManagedObjectContext:self.moc]];
[requestCodesForSale setPredicate:[NSPredicate predicateWithFormat:@"(%K.carrier.GUID == %@)",relationshipName,carrierGUID]];
NSError *error = nil; 
NSArray *codes = [self.moc executeFetchRequest:requestCodesForSale error:&error];
if (error) NSLog(@"Failed to executeFetchRequest to data store: %@ in function:%@", [error localizedDescription],NSStringFromSelector(_cmd)); 

NSNumber *count = [codes valueForKeyPath:@"@count.externalChangedDate"];
if (count == 0) { 
    [requestCodesForSale release];
    [pool drain], pool = nil;
    return YES;
}
NSDate *maxExternalChangedDate = [codes valueForKeyPath:@"@max.externalChangedDate"];

Answer 1

By using NSFetchRequest and returning NSDictionaryResultType You can use NSExpressionDescription to yeild the results for functions like max() and min().

Sample Code from Apple

NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"salary"];
NSExpression *maxSalaryExpression = [NSExpression expressionForFunction:@"max:"
                                                  arguments:[NSArray arrayWithObject:keyPathExpression]];

NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
[expressionDescription setName:@"maxSalary"];
[expressionDescription setExpression:maxSalaryExpression];
[expressionDescription setExpressionResultType:NSDecimalAttributeType];
[request setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]];

Check out this doc for more information.

Core Data Programming Guide