unable to add objects to saved collection in GAE using JDO

I have a ClassA containing an ArrayList of another ClassB

I can开发者_运维知识库 save a new instance of ClassA with ClassB instances also saved using JDO. However, When I retrieve the instance of Class A, I try to do like the below:

ClassA instance = PMF.get().getPersistenceManager().GetObjectByID( someid );
instance.GetClassBArrayList().add( new ClassB(...) );

I get an Exception like the below: Uncaught exception from servlet com.google.appengine.api.datastore.DatastoreNeedIndexException: no matching index found..

So I was wondering, Is it possible to add a new item to the previously saved collection? Or was it something I missed out.

Best Regards

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"no matching index found" Perhaps you need to add some index in GAE/J's datastore ? Nothing to do with JDO