Thanks! This really a smart way for relations that often changes. But I wonder if this is the only way?
What if the relation seldom change? I believe the cost of the indirection will be shown on the complexity of code and the runtime performance, if using the "resolution" Entity everywhere. On 1月20日, 下午3時37分, John Patterson <[email protected]> wrote: > If you are going to change the relation often you might want to have a > "resolution" Entity in the middle - lets say CurrentB. > > A->CurrentB->B > > instead of updating every A just update the single CurrentB > > On 20 Jan 2010, at 14:05, Alan She wrote: > > > > > Assume I have two class A and B, > > which is unidirection unowned many to one relationship. (A * ----> 1 > > B) > > I store the Key of class B inside class A. > > The code looks like this, (I am using JPA) > > > @Entity > > public class A { > > > �...@enumerated > > private Key bKey; > > } > > > @Entity > > public class B { > > } > > > Both A and B instance of the same user are under the same entity > > group. > > > When I need to delete B, lets say 'Bx' > > any A that associate with 'Bx' is going to change the association to > > 'By'. > > > I can do this by query and iterate update with low level API. > > However, there might be a huge amount of A, > > This will exceed the request time limit. > > > What's the best solution to solve this problem? > > Thanks!! > > -- > > 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 [email protected] > > . > > To unsubscribe from this group, send email to > > [email protected] > > . > > For more options, visit this group > > athttp://groups.google.com/group/google-appengine-java?hl=en > > .
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