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High Performance Core Data HighPerformanceCoreData.com MatthewMorey.com | @xzolian

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Agenda

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Managed Object Context Managed Object Managed Object Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Main Queue

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Memory Speed Less More Slow Fast

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Memory Speed Less More Slow Fast

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Memory Speed Less More Slow Fast

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Tools

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#define TICK NSDate *startTime = [NSDate date] #define TOCK NSLog(@"Elapsed Time: %f", -[startTime timeIntervalSinceNow])

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#define TICK NSDate *startTime = [NSDate date] #define TOCK NSLog(@"Elapsed Time: %f", -[startTime timeIntervalSinceNow]) ... TICK; [self methodYouWantToMeasure]; TOCK;

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-com.apple.CoreData.SQLDebug [1,2,3]

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-com.apple.CoreData.SQLDebug [1,2,3]

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-com.apple.CoreData.SQLDebug [1,2,3]

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-com.apple.CoreData.SQLDebug [1,2,3]

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-com.apple.CoreData.SQLDebug [1,2,3] -com.apple.CoreData.SyntaxColoredLogging 1 -com.apple.CoreData.MigrationDebug 1 -com.apple.CoreData.SQLiteDebugSynchronous [0,1,2] -com.apple.CoreData.SQLiteIntegrityCheck [1] -com.apple.CoreData.ConcurrencyDebug [1,2,3]

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$ sqlite3

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$ sqlite3 UFO.sqlite sqlite> select * from sqlite_master; table|ZUFOSIGHTING|ZUFOSIGHTING|3|CREATE TABLE ZUFOSIGHTING ( Z_PK...VARCHAR ) table|Z_PRIMARYKEY|Z_PRIMARYKEY|4|CREATE TABLE Z_PRIMARYKEY (Z_ENT...INTEGER) table|Z_METADATA|Z_METADATA|5|CREATE TABLE Z_METADATA (Z_VERSION...BLOB)

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sqlite> SELECT t0.ZSHAPE, COUNT( t0.ZSHAPE ) FROM ZUFOSIGHTING t0 GROUP BY t0.ZSHAPE; changed|1 changing|1546 chevron|760 cigar|1782 circle|5271 cone|265 ... teardrop|595 triangle|6082 unknown|4490

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SQLite Professional Pony Debugger

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Tools •Macros •Launch Arguments •SQL •Instruments •Measure, Measure, Measure

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Fetching

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NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; [fetchRequest setFetchBatchSize:20];

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NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; NSArray *UFOSightingsArray = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; NSMutableDictionary *uniqueShapesDictionary = [NSMutableDictionary dictionary]; for (UFOSighting *sighting in UFOSightingsArray) { ... // Count unique shape items ... } NSManagedObject

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NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; [fetchRequest setResultType:NSDictionaryResultType]; [fetchRequest setPropertiesToFetch:@"shape"]; ... // Count unique shape items ... NSDictionaryResultType

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NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; [fetchRequest setPredicate: [NSPredicate predicateWithFormat: @"shape == %@", @"sphere"]]; NSUInteger sphereCount = [self.managedObjectContext countForFetchRequest:fetchRequest error:&error]; ... // Repeat for each unique shape ... countForFetchRequest:error:

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NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init]; [expressionDescription setName:@"count"]; [expressionDescription setExpression: [NSExpression expressionForFunction:@"count:" arguments: @[[NSExpression expressionForKeyPath:@"shape"]]]]; [fetchRequest setPropertiesToFetch:@[@"shape", expressionDescription]]; [fetchRequest setPropertiesToGroupBy:@[@"shape"]]; [fetchRequest setResultType:NSDictionaryResultType]; NSExpression

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NSExpression NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init]; [expressionDescription setName:@"count"]; [expressionDescription setExpression: [NSExpression expressionForFunction:@"count:" arguments: @[[NSExpression expressionForKeyPath:@"shape"]]]]; [fetchRequest setPropertiesToFetch:@[@"shape", expressionDescription]]; [fetchRequest setPropertiesToGroupBy:@[@"shape"]]; [fetchRequest setResultType:NSDictionaryResultType];

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Prefetch Required Relationships

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[fetchRequest setRelationshipKeyPathsForPrefetching: @[@"photo"]];

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Fetch in the background

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[backgroundContext performBlock:^{ NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; fetchRequest.resultType = NSManagedObjectIDResultType; NSArray *managedObjectIDs = [backgroundContext executeFetchRequest:fetchRequest error:nil]; [mainQueueContext performBlock:^{ for (NSManagedObjectID *managedObjectID in managedObjectIDs) { UFOSighting *UFOSighting = [mainQueueContext objectWithID:managedObjectID]; // // Update UI on main queue // } }]; }];

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[backgroundContext performBlock:^{ NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; fetchRequest.resultType = NSManagedObjectIDResultType; NSArray *managedObjectIDs = [backgroundContext executeFetchRequest:fetchRequest error:nil]; [mainQueueContext performBlock:^{ for (NSManagedObjectID *managedObjectID in managedObjectIDs) { UFOSighting *UFOSighting = [mainQueueContext objectWithID:managedObjectID]; // // Update UI on main queue // } }]; }];

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[backgroundContext performBlock:^{ NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; fetchRequest.resultType = NSManagedObjectIDResultType; NSArray *managedObjectIDs = [backgroundContext executeFetchRequest:fetchRequest error:nil]; [mainQueueContext performBlock:^{ for (NSManagedObjectID *managedObjectID in managedObjectIDs) { UFOSighting *UFOSighting = [mainQueueContext objectWithID:managedObjectID]; // // Update UI on main queue // } }]; }];

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[backgroundContext performBlock:^{ NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"UFOSighting"]; fetchRequest.resultType = NSManagedObjectIDResultType; NSArray *managedObjectIDs = [backgroundContext executeFetchRequest:fetchRequest error:nil]; [mainQueueContext performBlock:^{ for (NSManagedObjectID *managedObjectID in managedObjectIDs) { UFOSighting *UFOSighting = [mainQueueContext objectWithID:managedObjectID]; // // Update UI on main queue // } }]; }];

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NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:”MyEntity”]; NSAsynchronousFetchRequest *async = [[NSAsynchronousFetchRequest alloc] initWithFetchRequest:request completionBlock^(id result) { if (result.finalResult) { ... } }]; [context performBlock: ^() { NSError *error = nil; asyncResult = [moc executeRequest:asyncRequest error:&blockError]; }]; iOS 8 | OS X Yosemite

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Fetching •Don’t fetch more than you need •Set a batch size •Let SQLite do the calculations •Prefetch required relationships •Fetch in the background

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Predicates

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Light Comparisons First

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[fetchRequest setPredicate: [NSPredicate predicateWithFormat: @"shape == %@ AND duration > %i", @"sphere", 30]];

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[fetchRequest setPredicate: [NSPredicate predicateWithFormat: @"shape == %@ AND duration > %i", @"sphere", 30]]; [fetchRequest setPredicate: [NSPredicate predicateWithFormat: @"duration > %i AND shape == %@", 30, @"sphere"]];

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Be cautious with strings

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Predicate Costs Less More Beginswith Endswith Equality == Contains Matches

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Predicate Costs Less More Beginswith Endswith Equality == Contains Matches [cd] cost you even more

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Predicates •Do light (numerical) comparisons first •Beginswith/Endswith instead of Contains/Matches •Don’t use [cd]

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Searching

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Canonicalize String Properties

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Canonicalize String Properties Description canonicalizedDesc Green Mën green men BEAM beam Prόbë probe ABDUCTION abduction

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CFStringNormalize((CFMutableStringRef)result, kCFStringNormalizationFormD); CFStringFold((CFMutableStringRef)result, kCFCompareCaseInsensitive | kCFCompareDiacriticInsensitive | kCFCompareWidthInsensitive, NULL);

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Canonicalized Tokens

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componentsSeperatedByCharactersInSet

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Separate Stack

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Primary Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Search Tokens

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Primary Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Search Tokens URIRepresentation

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Hash of Tokens

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Searching •Canonicalize text properties •Use tokens •Separate persistence stack •Hash of tokens

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Data Model

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Don’t Overnormalize

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Use External Storage

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Data Model •Don’t overnormalize •Use external storage for large attributes •Large blobs as separate entity •Less data takes less time to fetch

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App Launch

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“Lots of Things” Problem

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NSBatchUpdateRequest *batchRequest = [NSBatchUpdateRequest batchUpdateRequestWithEntityName: [RSSItem entityName]]; batchRequest.propertiesToUpdate = @{NSStringFromSelector(@selector(read)): [NSNumber numberWithBool:YES]}; batchRequest.resultType = NSStatusOnlyResultType; batchRequest.predicate = [NSPredicate predicateWithFormat:@"..."]; NSError *requestError; NSBatchUpdateResult *result = (NSBatchUpdateResult *)[self.managedObjectContext executeRequest:batchRequest error:&requestError]; if (result == nil) { NSLog(@"Error: %@", [requestError localizedDescription]); } else { // Batch update succeeded } iOS 8 | OS X Yosemite

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Importing Data

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Main Queue vs Private Queue self.managedObjectContext = self.persistenceStack.managedObjectContext; [self.managedObjectContext performBlockAndWait:^{ [self import]; }];

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Main Queue vs Private Queue NSManagedObjectContext *privateManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [privateManagedObjectContext setPersistentStoreCoordinator: self.managedObjectContext.persistentStoreCoordinator]; [privateManagedObjectContext performBlockAndWait:^{ [self import]; }];

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Typical Import Algorithm 1) JSON to NSDictionary 2) Find existing NSManagedObject 3) Optionally, create new NSManagedObject 4) Set attributes of new/updated NSManagedObject 5) Repeat for every JSON item

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Typical Import Algorithm 1) JSON to NSDictionary 2) Find existing NSManagedObject 3) Optionally, create new NSManagedObject 4) Set attributes of new/updated NSManagedObject 5) Repeat for every JSON item

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Efficient Import Algorithm 1) Sort import objects by ID 2) Execute a single fetch request for all matching IDs 3) Iterate through both import and existing objects 4) Update or create

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1 4 2 3 ... New Data

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1 4 2 3 ... New Data 4 1 ... Existing Data

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1 4 2 3 ... New Data 4 1 ... Existing Data

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1 4 2 3 ... New Data 4 1 ... Existing Data

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1 4 2 3 ... New Data 4 1 ... Existing Data

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1 2 3 4 ... New Data 1 4 ... Existing Data Update

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1 2 3 4 ... New Data 1 4 ... Existing Data Update

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1 2 3 4 ... New Data 1 4 ... Existing Data Insert

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1 2 3 4 ... New Data 1 4 ... Existing Data Insert

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2 1 2 3 4 ... New Data 1 4 ... Existing Data

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2 1 2 3 4 ... New Data 1 4 ... Existing Data

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1 2 3 4 ... New Data 1 4 ... Existing Data 2

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1 2 3 4 ... New Data 1 4 ... Existing Data 2 Insert

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1 2 3 4 ... New Data 1 4 ... Existing Data 2 Insert

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3 1 2 3 4 ... New Data 1 4 ... Existing Data 2

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3 1 2 3 4 ... New Data 1 4 ... Existing Data 2

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1 2 3 4 ... New Data 1 4 ... Existing Data 2 3 Update

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1 2 3 4 ... New Data 1 4 ... Existing Data 2 3 Update

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Efficient Import Algorithm With Batching 1) Sort import objects by ID 2) Execute multiple fetch request for matching IDs - Iterate through both import and existing objects - Update or create 3) Save Batch

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// Grab sorted persisted managed objects, based on the batch NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"UFOSighting"]; NSPredicate *fetchPredicate = [NSPredicate predicateWithFormat: @"%K IN %@", @"GUID", jsonBatchGUIDArray];

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// Grab sorted persisted managed objects, based on the batch NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"UFOSighting"]; NSPredicate *fetchPredicate = [NSPredicate predicateWithFormat: @"%K IN %@", @"GUID", jsonBatchGUIDArray];

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Pre-Populated SQLite File in App Bundle

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Download Pre-Populated SQLite File

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Importing Data •Do import work on private queues •Use efficient find-or-create algorithm •Work in batches to keep memory low •Use pre-populated SQLite file

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Memory

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[context refreshObject:UFOSightingManagedObject mergeChanges:NO];

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[context reset];

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Concurrency Models

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Managed Object Context Managed Object Managed Object Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Main Queue

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Managed Object Context Managed Object Managed Object Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Main Queue

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Managed Object Context Managed Object Managed Object Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Main Queue

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Context Did Save Notification Merge Changes From Notification

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Context Did Save Notification Merge Changes From Notification

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Context Did Save Notification Refetch and Reload

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Managed Object Context Private Queue UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates UI Work

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates UI Work Persisting to Disk

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Persistent Store Coordinator Persistent Store Model Main Queue Managed Object Context Private Queue Managed Object Context Managed Object Context Private Queue Background Updates UI Work Persisting to Disk __block NSManagedObjectContext *temporaryContext = self.workerObjectContext; __block NSManagedObjectContext *managedObjectContext = self.managedObjectContext; __block NSManagedObjectContext *writerObjectContext = self.writerManagedObjectContext; [temporaryContext performBlock:^{ NSError *error = nil; if (![temporaryContext save:&error]) { // TODO: Handle error } [managedObjectContext performBlock:^{ NSError *error = nil; if (![managedObjectContext save:&error]) { // TODO: Handle error } [writerObjectContext performBlock:^{ NSError *error = nil; if (![writerObjectContext save:&error]) { // TODO: Handle error } // Success!!! }]; // writerObjectContext }]; // managedObjectContext }]; // temporaryContext

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model Context Did Save Notification

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model Context Did Save Notification Merge Changes From Notification

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model Context Did Save Notification Merge Changes From Notification

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model Context Did Save Notification Refetch and Reload

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Persistent Store Coordinator Model Context Did Save Notification Refetch and Reload •Cannot pass objects between persistent store coordinators •Cannot pass objectIDs between persistent store coordinators •You can use URIRepresentation •You can use mergeChangesFromContextDidSaveNotification

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TLDR

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Managed Object Context Persistent Store Coordinator Persistent Store (SQLite, XML, ...) Model Managed Object Context Main Queue Private Queue Context Did Save Notification Refetch and Reload

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Concurrency Models •Use the simplest model that meets your needs •Update main context after large imports have completed

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Bang Head Here

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In general... •Use the tools, and measure, measure, measure •Don’t load more than you need to •Don’t use [cd] •Be smart with your data model •Import on a private queue in batches •Pick the correct (but simplest) concurrency model

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