I'm working on an iPhone app that gets a number of objects from a database. I'd like to store these using Core Data, but I'm having problems with my relationships.
A Detail contains any number of POIs (points of interest). When I fetch a set of POI's from the server, they contain a detail ID. In order to associate the POI with the Detail (by ID), my process is as follows:
Query the ManagedObjectContext for the detailID.
If that detail exists, add the poi to it.
If it doesn't, create the detail (it has other properties that will be populated lazily).
The problem with this is performance. Performing constant queries to Core Data is slow, to the point where adding a list of 150 POI's takes a minute thanks to the multiple relationships involved.
In my old model, before Core Data (various NSDictionary cache objects) this process was super fast (look up a key in a dictionary, then create it if it doesn't exist)
I have more relationships than just this one, but pretty much every one has to do this check (some are many to many, and they have a real problem).
Does anyone have any suggestions for how I can help this? I could perform fewer queries (by searching for a number of different ID's), but I'm not sure how much this will help.
Some code:
POI *poi = [NSEntityDescription
insertNewObjectForEntityForName:@"POI"
inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]];
poi.POIid = [attributeDict objectForKey:kAttributeID];
poi.detailId = [attributeDict objectForKey:kAttributeDetailID];
Detail *detail = [self findDetailForID:poi.POIid];
if(detail == nil)
{
detail = [NSEntityDescription
insertNewObjectForEntityForName:@"Detail"
inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]];
detail.title = poi.POIid;
detail.subtitle = @"";
detail.detailType = [attributeDict objectForKey:kAttributeType];
}
-(Detail*)findDetailForID:(NSString*)detailID {
NSManagedObjectContext *moc = [[UIApplication sharedApplication].delegate managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription
entityForName:@"Detail" inManagedObjectContext:moc];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];
NSPredicate *predicate = [NSPredicate predicateWithFormat:
@"detailid == %@", detailID];
[request setPredicate:predicate];
NSLog(@"%@", [predicate description]);
NSError *error;
NSArray *array = [moc executeFetchRequest:request error:&error];
if (array == nil || [array count] != 1)
{
// Deal with error...
return nil;
}
return [array objectAtIndex:0];
}
