hi robin! On Sep 11, 11:34 am, Robin B <[email protected]> wrote:
> Transactions on root entities are supposed to be independent, which > would means you would get many Posts with key_name='foobar'. However, > if the transactions are not independent, you will get write > contention, which is not supposed to happen when using root entities. > > How could the datastore provide both transactional uniqueness of > key_names across root entities and transactional independence for root > entities? Its a paradox. good question! the key point is that transactions on *different* entity groups are independent. entity groups are uniquely identified by root entity key, and in this example, there's only one root entity, the Post entity with key name foobar. there can never exist more than one of that root entity, since keys have to be unique. so, running this transaction on key name foobar will always operate on the same entity group, so you may see contention, but you'll never see it insert multiple Post/foobar entities. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
