If you choose to model the attribute as an entity, you would use an unowned relationship since owned entities can only have a single parent. If attributes are simple strings, you can just use a multi-valued (List) property of strings. Some cars will have the same string attributes, but this shouldn't cause a huge effect on performance or cost, assuming you don't have too many attributes per car. - Jason
On Tue, Aug 25, 2009 at 8:25 PM, Iain <iain.robe...@gmail.com> wrote: > > Do you really need one instance of the attribute? If so I suggest > unowned, and use transactions to avoid duplicates. Read this artical: > http://code.google.com/appengine/docs/java/datastore/transactions.html > If performance is not a concern, use a one-many > http://code.google.com/appengine/docs/java/datastore/relationships.html > > If you do not care about one instance of the attrbite, use a > collection. This will also perform better as you only load one entity. > > http://code.google.com/appengine/docs/java/datastore/dataclasses.html#Collections > > > > > > On Aug 26, 12:23 pm, mar_novice <mariocape1...@gmail.com> wrote: > > Situation.. > > I have two class, Car and Attribute > > A car can have zero or more attributes and Cars can have the same > > attribute. > > > > Now for example > > I created an instance of a car names X and has an attribute of Big. > > ------------------ --------------------------------- > > | Car | | Attribute | > > ----------------- ---------------------------------- > > | X | | Big | > > | | | > > | > > > > now what if I created another instance of a car named Y and it has > > also an attribute of Big and Fast.. > > > > ------------------ --------------------------------- > > | Car | | Attribute | > > ----------------- ---------------------------------- > > | X | | Big | > > | Y | | Big | > > | | | Fast | > > > > What is the proper approach so that the Big instance of attribute will > > not be duplicated? And should I use one to many relationship? Also it > > is owned or unowned? > > > > Thanks in advance for helping out.. > > > > -mar_novice > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
