Somehow with the error message looks like both your queries are still happening in the same transaction. Are you sure that the transaction boundaries of both the methods are separate? To check this I would separate the 2 out into 2 methods each having their own transaction start and end or @Transactional if you are using Spring. Then with a third method I would invoke the first, work on the results if anything to do and then invoke the second and observe if I still get the same error. You could also try to run the first one without a transaction since it is a fetch and if it is suits your application to execute it without the tx.
Regards | Vikas www.inphina.com On Sep 27, 10:46 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.
