Hello All!
(this is the same in plain text)
Summary: It looks like [NSManagedObjectContext executeFetchRequest:error:]
starts to evaluate a predicate ([NSPredicate evaluateWithObject:]) with objects
that was not requested and was not fetched from
a database.
Our application makes prefetching of CoreData entities with relationships like
NSFetchRequest* requestRelatedTags = [[[NSFetchRequest alloc] init]
autorelease];
[requestRelatedTags setEntity:[NSEntityDescription entityForName :
kFSIValueElementA inManagedObjectContext : [md managedObjectContext ]] ];
[requestRelatedTags setFetchLimit: 1000000 ];
NSPredicate * predicate = [ NSPredicate predicateWithFormat: @"(self IN
%@)",[items valueForKey: @"objectID"]];
[requestRelatedTags setPredicate:predicate];
[requestRelatedTags setRelationshipKeyPathsForPrefetching : [ NSArray
arrayWithObjects: @"tags", nil]];
[requestRelatedTags setReturnsObjectsAsFaults: true];
items0_ = [[md managedObjectContext] executeFetchRequest : requestRelatedTags
error: nil];
where "items" is an array of 100 NSManagedObjects, "tags" is to-many
relationship of the kFSIValueElementA entity with inverse to-one relationship.
At start this code works quickly and takes fixed amount of time (0.03-0.04 sec)
every time. But at some point it starts to work very slowly taking more and
more time. Instruments shows that it fetches 100 objects
every time from a database. But Shark shows that it uses [NSPredicate
evaluateWithObject:] more and more times. To be precise, it invokes
[NSPredicate evaluateWithObject:] 100 times more every time.
[NSPredicate evaluateWithObject:] is invoked every time from
[NSManagedObjectContext executeFetchRequest: error:].
We added logging to [NSPredicate evaluateWithObject:] and we see that it is
evaluated on objets that was not requested by the fetch request and was not
fetched from the SQLite database. Thus this is a bug
in [NSManagedObjectContext executeFetchRequest:error:]. It should not filter
objects that was not.
Does anybody have any ideas how to solve this problem?
Best Regards,
Oleksiy Gorelov
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