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Fix synchronous data removal from PixelDataStore cache #382

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Dec 22, 2021
Merged

Fix synchronous data removal from PixelDataStore cache #382

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3 changes: 1 addition & 2 deletions DuckDuckGo/Statistics/PixelDataStore.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -164,6 +164,7 @@ final class LocalPixelDataStore<T: NSManagedObject>: PixelDataStore {
}

func removeValue(forKey key: String, completionHandler: ((Error?) -> Void)?) {
self.cache.removeValue(forKey: key)
let predicate = self.predicate(forKey: key)

func mainQueueCompletion(_ error: Error?) {
Expand All @@ -185,8 +186,6 @@ final class LocalPixelDataStore<T: NSManagedObject>: PixelDataStore {
let changes: [AnyHashable: Any] = [NSDeletedObjectsKey: deletedObjects]
NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [context])

self.cache.removeValue(forKey: key)
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What are the odds that the try call earlier in this function fails? In that case, we'll have data removed from the cache but not from the DB. Is it worth repairing the cache in the catch block in case this happens? Admittedly I think the chances are slim.

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the cache is the source of truth here and if we get an error here it would be the database that needs to be restored - we've discussed this on our last Apple team meeting and this will be handled as a separate task


mainQueueCompletion(nil)
} catch {
mainQueueCompletion(error)
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