:D

gistfile1.txt

        int count;
        int* countPtr = &count;

        NativeKeyValueArrays<int, UnsafeEventBatch> pairsMaster = default;
        NativeArray<Entity> entitiesMaster = default;

        var pairsPtr = UnsafeUtility.AddressOf(ref pairsMaster);
        var entitiesPtr = UnsafeUtility.AddressOf(ref entitiesMaster);

        var sw = Stopwatch.StartNew();

        Job.WithCode(() =>
        {
            ref var pairs = ref UnsafeUtilityEx.AsRef<NativeKeyValueArrays<int, UnsafeEventBatch>>(pairsPtr);
            ref var entities = ref UnsafeUtilityEx.AsRef<NativeArray<Entity>>(entitiesPtr);

            pairs = map.GetKeyValueArrays(Allocator.Temp);

            for (int i = 0; i < pairs.Keys.Length; i++)
            {
                var batchCount = pairs.Values[i].Queue.Count();
                *countPtr += batchCount;
            }
           
            entities = new NativeArray<Entity>(*countPtr, Allocator.TempJob);

        }).Run();

        sw.Stop();
        Debug.Log($"Time={sw.Elapsed.TotalMilliseconds:N4}");