CoreData predicate and fetch input takes way to long

Question

I have this piece of code:

-(void)createArtistsFromArray:(NSArray*)jsonAttrArr {

    NSError *fetchError = nil;
    if (jsonAttrArr) {

        for(NSMutableDictionary *dic in jsonAttrArr) {

            NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
            [fetchRequest setEntity:[NSEntityDescription entityForName:@"Artists" inManagedObjectContext:[sharedAppDelegate managedObjectContext]]];
            NSPredicate *predicateById = [NSPredicate predicateWithFormat:@"artistId == %@", [dic objectForKey:@"artistId"]];
            [fetchRequest setPredicate:predicateById];

            NSArray *categorisItems = [[sharedAppDelegate managedObjectContext] executeFetchRequest:fetchRequest error:&fetchError];

            Artists *artistObj = [NSObject returnItemUsingFetchingResults:categorisItems andEntityName:@"Artists"];
            [self setAttrForEntity:artistObj withDictionary: dic];
            [self createElementEntityFromDictionary:dic andArtist:artistObj];


        }

    }
    NSError *error;
    if (![[sharedAppDelegate managedObjectContext] save:&error])
        NSLog(@"Error saving - error:%@" , error);

}

-(IBAction)createElementEntityFromDictionary:(id)sender andArtist:(Artists*)aObj {

    NSMutableOrderedSet* setWithElements = [[NSMutableOrderedSet alloc] init];
    NSError *fetchError = nil;

        NSArray *elements = [(NSDictionary*)sender objectForKey:@"elements"];

        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        [fetchRequest setEntity:[NSEntityDescription entityForName:@"Element" inManagedObjectContext:[sharedAppDelegate managedObjectContext]]];

        int forCounter = 0;
        for (NSDictionary *elementInputDictionary in elements) {

            [fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"elementId == %i", [[elementInputDictionary objectForKey:@"elementId"] integerValue]]];
            NSArray *items = [[sharedAppDelegate managedObjectContext] executeFetchRequest:fetchRequest error:&fetchError];

            Element* outputElement = [NSObject returnItemUsingFetchingResults:items andEntityName:@"Element"];
            [outputElement setCatId:aObj.artistId];
            [outputElement setOrderNo:forCounter];

            [self setAttrForEntity:outputElement withDictionary: elementInputDictionary];

            outputElement.images = [self setImagesToElement:outputElement fromList:[elementInputDictionary objectForKey:@"imagesList"]];
            [setWithElements addObject: outputElement];
            forCounter++;


        aObj.elements = setWithElements;
    }

    NSError *error;
    if (![[sharedAppDelegate managedObjectContext] save:&error]) {
        NSLog(@"Error saving - error:%@" , error);
    }

}

-(void)setAttrForEntity:(id)entityName withDictionary:(NSDictionary*)attrDictionary {
    NSDictionary *attributes = [[entityName entity] attributesByName];
    for (NSString *attribute in attributes) {
        id value = [attrDictionary objectForKey:attribute];
        if (!value) continue;
        [entityName setValue:value forKey:attribute];
    }
}

In Category NSObject:

+(id)returnItemUsingFetchingResults:(NSArray*)fResults andEntityName:(NSString*)name {
    if([fResults isEmpty])
        return [NSEntityDescription insertNewObjectForEntityForName:name inManagedObjectContext:[sharedAppDelegate managedObjectContext]];
    else
        return [fResults firstObject];
}

And this operation take some time (for 800 Artists entity about 45 seconds). This is normal? Or maybe there something wrong with my approach here?

This is my data model: enter image description here

score 1 · Accepted Answer · edited May 23 '17 at 11:57

Few suggestions here.

First. To import data in a efficient manner I would follow my previous answer on it: What is the most efficient way to sync Core Data with JSON API.

Second. Moving the code in a background thread could be good since in this way you avoid main thread to freeze. Display a wait indicator to the user. Here you can take advantage of new CD API (since iOS 5) or the traditional way. Some notes here: iPhone iOS how to merge Core Data NSManagedObjectContext?.

About your question. I think it's normal the import takes so much time. You perform queries selecting specific objects. Anyway the code can be modified following the first link.

Hope it helps.

CoreData predicate and fetch input takes way to long

1 Answers1