On Oct 17, 11:05 pm, "Max Ross (Google)" <max.r...@gmail.com> wrote: > We debated this quite a bit internally. To paraphrase the argument that > carried the day: > XG transactions are awesome but they are not true global transactions. > You're limited to 5 entity groups, you're more likely to see partially > applied transactions in global query results, you can get a concurrency > exception from a *read*, and there is a performance impact (when you've got > more than 1 entity group enlisted). In short, there's some > surprising/subtle stuff that we really want developers to understand before > they start using this feature. > > If we didn't require opt-in it would be too easy for our new developers > (particularly those coming from the RDBMS world where global transactions > are the norm) to miss these important considerations. We want it to be > super easy to use the Datastore, but creating a false sense of simplicity > can do more harm than good in the long run.
One other consideration: XG transactions do not work on master/slave. While the default could be different depending on whether HRD is used, that definitely has drawbacks. David Gay -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
