Hello All! 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 : [ N
SArray 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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