billibala / BatchInsertAndUniqueConstraints

Demonstrate batch insert error when unique constraint contains multiple attributes

BatchInsertAndUniqueConstraints

This sample code study the issue related to Core Data batch insert.

When unique constraint is set to multiple attributes (compound key), batch insert fails.

You can refer to EventSession for unique constraint configuration with multiple attributes (eventID and sessionID)

This is a screen recording of the problem.

How to use the sample code?

• Run the app target
• To batch insert "events", click "Event Batch Insert"
• To batch insert "sessions", click "Session Batch Insert"

Test Result

• "event" insert always succeeds.
• "session" insert succeeds the first time. All subsequent attempt will fail with error.

Error Domain=NSCocoaErrorDomain Code=134050 "(null)" UserInfo={NSExceptionOmitCallstacks=true, _NSCoreDataOptimisticLockingFailureConflictsKey=( )}

Now... to eliminate the error...

• Remove eventID from unique constraint in EventSession entity.
• Run the sample code again.
• Now, clicking "Session Batch Insert" multiple times. Batch insert will go through. No Core Data error.

Possible further investigation

Enable Core Data debug log: -com.apple.CoreData.SQLDebug 1