CODEWITHSUNDEEP
ioscore-dataquery-optimization
Chris Wagner
Chris Wagner

Reputation: 21003

Optimized Core Data fetch for most recently modified object

I am trying to optimize a fetch request for Core Data.

I have an entity with an attribute called lastModifiedDate that is an NSDate object. I need to query my database for the most recent lastModifiedDate property. I have the following code which works fine in small datasets, but with a database that has 40k records this query runs like crap.

NSDate *mostRecentLastModifiedDate = nil;
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:entityName inManagedObjectContext:self.managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
[request setFetchLimit:1];
[request setPropertiesToFetch:[NSArray arrayWithObject:@"lastModifiedDate"]];

NSSortDescriptor *dateSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"lastModifiedDate" ascending:NO];

[request setSortDescriptors:[NSArray arrayWithObject:dateSortDescriptor]];
[dateSortDescriptor release];

NSError *error = nil;
NSArray *result = [self.managedObjectContext executeFetchRequest:request error:&error];
if (error) {
    NSLog(@"Error fetching most recent lastModifiedDate property for %@ entity, error details: %@", entityName, error);
} else if ([result count] > 0) {
    mostRecentLastModifiedDate = [[[[result objectAtIndex:0] valueForKey:@"lastModifiedDate"] copy] autorelease];
} else {
    mostRecentLastModifiedDate = [NSDate distantPast];
}

[request release];

return mostRecentLastModifiedDate;

Upvotes: 1

Views: 383

Answers (1)

Chris Wagner
Chris Wagner

Reputation: 21003

Marking the lastModifiedDate attribute as indexed in the Data Model made this query extremely fast, would still be interested if there is a better approach to do this though.

Upvotes: 1

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