High Performance Core Data

http://highperformancecoredata.com/

Learn how to analyze, debug, and squeeze every last bit of performance out of Core Data. The standard Core Data implementation is very powerful and flexible but lacks performance. In this advanced session we will cover various performance analysis tools, model optimization, and various high performance concurrency models. This is an advanced discussion that assumes you have used Core Data before.

Transcript

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

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2. Agenda
   

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

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4. Memory
   Speed
   Less More
   Slow Fast
   

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5. Memory
   Speed
   Less More
   Slow Fast
   

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6. Memory
   Speed
   Less More
   Slow Fast
   

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7. View Slide

8. View Slide

9. Tools
   

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

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

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

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

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

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

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16. -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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17. $ sqlite3
    

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18. $ 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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19. 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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20. SQLite
    Professional
    Pony Debugger
    

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22. View Slide

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

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24. Fetching
    

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25. View Slide

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

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27. View Slide

28. View Slide

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

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31. 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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32. 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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33. 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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34. View Slide

35. Prefetch Required Relationships
    

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

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37. Fetch in the background
    

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38. [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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39. [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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40. [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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41. [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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42. 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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43. 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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44. Predicates
    

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45. Light Comparisons First
    

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

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

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48. Be cautious with strings
    

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49. Predicate
    Costs
    Less More
    Beginswith
    Endswith
    Equality
    ==
    Contains
    Matches
    

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

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

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52. Searching
    

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53. Canonicalize String Properties
    

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

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

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56. Canonicalized Tokens
    

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57. View Slide

58. View Slide

59. componentsSeperatedByCharactersInSet
    

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60. Separate Stack
    

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61. 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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62. 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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63. Hash of Tokens
    

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

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65. Data Model
    

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66. Don’t Overnormalize
    

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67. Use External Storage
    

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68. View Slide

69. View Slide

70. View Slide

71. View Slide

72. 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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73. App Launch
    

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74. “Lots of Things”
    Problem
    

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75. 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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76. Importing Data
    

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77. View Slide

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

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

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80. View Slide

81. 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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82. 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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83. 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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84. 1
    4
    2
    3
    ...
    New Data
    

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85. 1
    4
    2
    3
    ...
    New Data
    4
    1
    ...
    Existing Data
    

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86. 1
    4
    2
    3
    ...
    New Data
    4
    1
    ...
    Existing Data
    

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87. 1
    4
    2
    3
    ...
    New Data
    4
    1
    ...
    Existing Data
    

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88. 1
    4
    2
    3
    ...
    New Data
    4
    1
    ...
    Existing Data
    

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89. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    Update
    

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90. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    Update
    

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91. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    Insert
    

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92. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    Insert
    

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93. 2
    1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    

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94. 2
    1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    

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95. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    2
    

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96. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    2
    Insert
    

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97. 1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    2
    Insert
    

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98. 3
    1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    2
    

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99. 3
    1
    2
    3
    4
    ...
    New Data
    1
    4
    ...
    Existing Data
    2
    

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100. 1
     2
     3
     4
     ...
     New Data
     1
     4
     ...
     Existing Data
     2
     3
     Update
     

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101. 1
     2
     3
     4
     ...
     New Data
     1
     4
     ...
     Existing Data
     2
     3
     Update
     

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102. View Slide

103. 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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104. // 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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105. // 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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106. Pre-Populated SQLite
     File in App Bundle
     

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107. Download Pre-Populated
     SQLite File
     

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108. 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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109. Memory
     

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110. [context refreshObject:UFOSightingManagedObject
     mergeChanges:NO];
     

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111. [context reset];
     

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112. Concurrency
     Models
     

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

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

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

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

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

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

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119. 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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120. 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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121. 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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122. Persistent Store
     Coordinator
     Persistent Store
     Model
     Main Queue
     Managed Object
     Context
     Managed Object
     Context
     Private Queue
     

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

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124. 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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125. 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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126. 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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127. 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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128. 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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129. 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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130. 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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131. 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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132. 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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133. 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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134. 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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135. 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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137. 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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138. 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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139. 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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140. 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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141. 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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142. 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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143. 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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144. 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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145. View Slide

146. 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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147. TLDR
     

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

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150. Bang
     Head
     Here
     

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151. 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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152. Questions?
     HighPerformanceCoreData.com
     MatthewMorey.com | @xzolian
     BuoyExplorer.com - Marine Conditions App
     WristPresenter.com - Presentation App
     ChaiOne.com - Hiring remote iOS engineers
     

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