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Code Issues 95 Packages Projects Releases 10 Wiki Activity

Fixes #98 (deadlock when merge happens while main queue is querying)

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This commit is contained in:
Colin Morelli
2016-09-29 14:47:51 -04:00
parent ed8c7b35e8
commit 8be20370d5
3 changed files with 33 additions and 7 deletions
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8
Sources/Internal/NSManagedObjectContext+Transaction.swift
View File

@@ -101,8 +101,8 @@ internal extension NSManagedObjectContext {
}
@nonobjc
internal func saveSynchronously() -> SaveResult {
internal func saveSynchronously(mergeSynchronously: Bool = true) -> SaveResult {
var result = SaveResult(hasChanges: false)
self.performBlockAndWait {
@@ -114,7 +114,7 @@ internal extension NSManagedObjectContext {
do {
self.isSavingSynchronously = true
self.isSavingSynchronously = mergeSynchronously
try self.save()
self.isSavingSynchronously = nil
}
@@ -131,7 +131,7 @@ internal extension NSManagedObjectContext {
if let parentContext = self.parentContext where self.shouldCascadeSavesToParent {
switch parentContext.saveSynchronously() {
switch parentContext.saveSynchronously(mergeSynchronously) {
case .Success:
result = SaveResult(hasChanges: true)

28
Sources/Transactions/SynchronousDataTransaction.swift
View File

@@ -59,7 +59,33 @@ public final class SynchronousDataTransaction: BaseDataTransaction {
self.result = result
return result
}
/**
Saves the transaction changes and waits for completion synchronously, but merges into the main context asynchronously. This method should not be used after the `commit()` method was already called once.
This method can be used to avoid potential deadlocks that can arise when a background thread attempts to merge changes into the main context while the main queue is querying from that context. Note that this
introduces a possibility that the main thread can attempt to query for the changes before the asynchronous merge operation has happened.
- returns: a `SaveResult` containing the success or failure information
*/
public func commit() -> SaveResult {
CoreStore.assert(
self.transactionQueue.isCurrentExecutionContext(),
"Attempted to commit a \(cs_typeName(self)) outside its designated queue."
)
CoreStore.assert(
!self.isCommitted,
"Attempted to commit a \(cs_typeName(self)) more than once."
)
self.isCommitted = true
let result = self.context.saveSynchronously(false)
self.result = result
return result
}
/**
Begins a child transaction synchronously where `NSManagedObject` creates, updates, and deletes can be made. This method should not be used after the `commit()` method was already called once.