Be sure your "update User4" method does not involve operations on the other user objects.
Sometimes relations between objects are hidden in the model, i.e. maybe you have something like a key for the other users in User4 (I'm thinking about a "friends list" or similar things implemented). In this case if you perform operations on those entities you may get the error message. Regards Lorenzo On Sep 27, 7:46 am, Yousuf Haider <yousuf.r...@gmail.com> wrote: > First off I know that you can't operate on entities in different entity > groups within the same transaction. My question is around a problem I am > having where I am querying for certain entities (each in a different entity > group) outside a txn and then I start a txn where I operate on an entity in > a different entity group. > > In my model I have a root entity called User. So each instance of User will > be in a different entity group. > > Here is what I am doing in pseudo-code: > > *Request comes in > > Create EntityManager > > Execute a JPA query using this EntityManager to retrieve the keys for all > User entities satisfying a particular criteria (say we got UserKey1, > UserKey2, UserKey3 back) > > Using EntityManager Start a txn > Retrieve User with id : UserKey4 (notice this is different from the ones > we retrieved above) > Update this User object. > Commit txn <<<<<<<<<<<<<<<<<<<<<<< Intermittently > fails here > Close EntityManager > > Return response > * > > Notice here that the initial query is not part of the transaction that is > subsequently created.* Inside that transaction only a single entity group is > operated upon* (the Entity group for User object UserKey4). > > The first time the request goes in (after a server start) this code > intermittently fails. Every subsequent request fails pretty consistently. > > The exception occurs at the commit with the infamous: "can't operate on > multiple entity groups" exception. The 2 entities listed in the exception > are the following: > 1. the UserKey4 > 2. One of the User objects whose keys were returned in the initial query. > > This is really weird since within the txn I am operating on a single entity > group. If my understanding is correct I should be able to do this. > > The only rational reason why this is happening might be that even querying > for objects outside a txn and any subsequent txn should deal with entities > in the same entity group. Is that the case or am I missing something here ? > > I have not been able to find a definite answer to this in the documentation > so thought I'd try the mailing list. > > Thanks > Yousuf -- 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-j...@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.
