public void On(DocumentDescriptorInitialized e)
        {
            var descriptor = _blobStore.GetDescriptor(e.BlobId);

            if (descriptor != null)
            {
                _collection.Upsert(e, e.HandleInfo.FileName.Extension,
                                   () => new DocumentStats()
                {
                    Files = 1,
                    Bytes = descriptor.Length
                },
                                   s =>
                {
                    s.Files++;
                    s.Bytes += descriptor.Length;
                });
            }
        }