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POPerformance considerations on deleting Managed Objects using Cascade rule in Core Data
 

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  1. POPerformance considerations on deleting Managed Objects using Cascade rule in Core Data
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    <p>I searched within SO but I didn't find a any suggestions to boost performances on deleting Managed Object in Core Data when dealing with relationships.</p> <p>The scenario is quite simple.<img src="https://i.stack.imgur.com/WWeKP.png" alt="enter image description here"></p> <p>As you can see there are three different entities. Each entity is linked in cascade with the next. For example, <code>FirstLevel</code>has a relationship called <code>secondLevels</code> to <code>SecondLevel</code>. The delete rule from <code>FirstLevel</code> to <code>SecondLevel</code> is <strong>Cascade</strong> while the delete rule from <code>SecondLevel</code> to <code>FirstLevel</code> is <strong>Nullify</strong>. The same rules are applied between <code>SecondLevel</code> and <code>ThirdLevel</code>.</p> <p>When I want to delete the entire graph, I perform a method like the following:</p> <pre><code>NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"FirstLevel" inManagedObjectContext:context]; [fetchRequest setEntity:entity]; NSError *error = nil; NSArray *items = [context executeFetchRequest:fetchRequest error:&amp;error]; [fetchRequest release]; // delete roots object and let Core Data to do the rest... for (NSManagedObject *managedObject in items) { [context deleteObject:managedObject]; } </code></pre> <p>Taking advantage of the <strong>Cascade</strong> rule the graph is removed. This works fast for few objects but decreases performances for many objects. In addition, I think (but I'm not very sure) that this type of deletion performs a lot of round trips to the disk, Am I wrong?</p> <p>So, my question is the following: how is it possible to remove the graph without taking advantage of <strong>Cascade</strong> rule and boost performances but, at the same time, maintain graph consistency?</p> <p>Thank you in advance.</p> <p><strong>EDIT</strong></p> <p>I cannot delete the entire file since I have other entities in my model.</p> <p><strong>EDIT 2</strong></p> <p>The code I posted is wrapped in the <code>main</code> method of a <code>NSOperation</code> subclass. This solution allows the deleting phase to be excuted in background. Since I took advantage of <strong>Cascade Rule</strong> the deletion is performed in a semi automatic way. I only delete root objects, the <code>FirstLevel</code> items, by means of the for loop within the posted code. In this way Core Data to do the rest for me. What I'm wondering is the following: is it possible to bybass that semi-automatic delete operation and do it manually without losing the graph consistency?</p>
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    1. USLorenzo B
    1. USLorenzo B
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    1. CODo tou want to delete the whole graph,i mean, clear all the persistent store,or just some branches?
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      1. USNikita Pestrov
    2. COThe whole graph.
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    3. COThenmaybe this will help you?http://stackoverflow.com/questions/3266084/how-to-remove-all-objects-from-core-data
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      1. POPerformance considerations on deleting Managed Objects using Cascade rule in Core Data
      1. USNikita Pestrov
 

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