transaction-collision

Transaction collision for sequential insert on Google App Engine. Why?

I am inserting a set of records on Google App Engine. I insert them in batch to avoid deadline exceptions. When there is a large number of records (for example 1k) I always receive an unexpected: Transaction collision for entity group with key datastore_types.Key.from_path(u'GroupModel', u'root', _app=u'streamtomail'). R...