> Yes, I understand transactions and entity groups. Why do you need to > create an entity group *atomically*?
For the same reason that transactions are useful - incomplete groups are wrong (in my application) and I'd rather not deal with them. > If you create a new entity, it will automatically be assigned a unique > key at the datastore level. What's wrong with just using that? Each db.put has significant overhead. If I can generate a unique name without a db.put, I can reduce the number of db.puts that my application does by a factor of 2. On Nov 22, 5:07 pm, "David Symonds" <[EMAIL PROTECTED]> wrote: > On Sun, Nov 23, 2008 at 8:50 AM, Andy Freeman <[EMAIL PROTECTED]> wrote: > >> > Suppose that I want to atomically create an entity group with two > >> > nodes, one the parent of the other. > >> But *why* exactly do you want to do this? > > > Because I want "a set of one or more entities that can be manipulated > > in a single transaction. Entity group relationships tell App Engine to > > store several entities in the same part of the distributed network. A > > transaction sets up datastore operations for an entity group, and all > > of the operations are applied as a group, or not at all if the > > transaction fails." > > Yes, I understand transactions and entity groups. Why do you need to > create an entity group *atomically*? > > > The fact that GAE uses many machines and concurrently is why the full > > hostname, IP, or MAC address or some other machine identifier is > > useful in creating a unique identifier on GAE. (If my application > > always ran on the same machine, the process id and time would be > > sufficient.) > > If you create a new entity, it will automatically be assigned a unique > key at the datastore level. What's wrong with just using that? > > Dave. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com 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 -~----------~----~----~----~------~----~------~--~---