Iphone – Core Data store corruption

core-dataiphonesqlite

A handful of customers for my iPhone app are experiencing Core Data store corruption (I assume so, since the error is "Failed to save to data store: Operation could not be completed. (Cocoa error 259.)")

Has anyone else experienced this kind of store corruption? I am worried since I aim to soon push an update which performs a schema migration, and I am worried that this will expose even more problems.

I had assumed that the Core Data/SQLlite APIs use atomic operations and are immune to corruption except if the underlying filesystem experiences corruption.

Is there a way to reduce/prevent corruption, and a way to reproduce the corruption so I can test this (I have been unsuccessful thus far).

Edit:

Also getting this error: "The database at /var/mobile/Applications//Documents/foo.sqlite is corrupted. SQLite error code 11, database disk image is malformed."

Best Answer

It happens to me when I manually overwrote my Base.sqlite without deleting Base.sqlite-wal and Base.sqlite-shm. Indeed, these files are new SQLite 3.7 features, maybe added in iOS 7.

To resolve the problem, I deleted Base.sqlite-* and sqlite regenerated them from my new base version.

iOS 9 and later:

iOS 9 added a new class called NSBatchDeleteRequest that allows you to easily delete objects matching a predicate without having to load them all in to memory. Here's how you'd use it:

Swift 5

let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Car")
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)

do {
    try myPersistentStoreCoordinator.execute(deleteRequest, with: myContext)
} catch let error as NSError {
    // TODO: handle the error
}

Objective-C

NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Car"];
NSBatchDeleteRequest *delete = [[NSBatchDeleteRequest alloc] initWithFetchRequest:request];

NSError *deleteError = nil;
[myPersistentStoreCoordinator executeRequest:delete withContext:myContext error:&deleteError];

More information about batch deletions can be found in the "What's New in Core Data" session from WWDC 2015 (starting at ~14:10).

iOS 8 and earlier:

Fetch 'em all and delete 'em all:

NSFetchRequest *allCars = [[NSFetchRequest alloc] init];
[allCars setEntity:[NSEntityDescription entityForName:@"Car" inManagedObjectContext:myContext]];
[allCars setIncludesPropertyValues:NO]; //only fetch the managedObjectID

NSError *error = nil;
NSArray *cars = [myContext executeFetchRequest:allCars error:&error];
[allCars release];
//error handling goes here
for (NSManagedObject *car in cars) {
  [myContext deleteObject:car];
}
NSError *saveError = nil;
[myContext save:&saveError];
//more error handling here

Edit:

Best Answer

Related Solutions

Sqlite – Store boolean value in SQLite

Ios – Core Data: Quickest way to delete all instances of an entity

iOS 9 and later:

Swift 5

Objective-C

iOS 8 and earlier:

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