Thanks for all the replies, just a quick question. Since BigTable is object database so why bother having relationship between entities? I know there are advantages to that. But for small application like school project, I think I dont really need to have all those relationship annotations in relevant data model. I mean you can simply "join" the query result from the app context? For example if I have forum board containing few fields including forum category (e.g Science, Tech, etc) and forum group (adult/teen/kids). In RDBMS, forum category id and forum group id will be stored in Forum table as foreign key which make them related. but for BigTable, the only way to relate them is using the mappedBy annotation or embedded class(not really a relationship).
Im thinking not to have the relationship set in the relevant class and simply tie everything at app level. for example after querying the forum object, it will list and display all forum topics according to category and group. Since forumcategoryid and forumgroupid are stored as Long type in forum object, displaying series of number is meaningless. so basically I can create a function that will query this id to respective objects and return the forum category description based on ID supplied. Any advice? btw, ive gone through the links u given, but there isnt enough app-like example on one-to-many relationship (only the simple guestbook example) On Tue, Jul 26, 2011 at 8:21 PM, Jose Montes de Oca < [email protected]> wrote: > Hi, > > You don't need to worry much on the underlying of the datastore (big table) > but rather understand how the datastore works as a non relational way of > persisting data in your application. If you are using Java you have: > > - JPO: http://code.google.com/appengine/docs/java/datastore/jdo/ > - JPA: http://code.google.com/appengine/docs/java/datastore/jpa/ > > There are also other frameworks that you can check out: > - Objectify: http://code.google.com/p/objectify-appengine/ > - slim3: http://code.google.com/p/slim3/ > - Twig: http://code.google.com/p/twig-persist/ > > I will recommend to start by reading about the Datastore: > http://code.google.com/appengine/docs/java/datastore/overview.html getting > familiar with its concept (keys, properties, entities, ancestors ...) > > Another good resource of information would be Past Google IO talks: > - http://www.youtube.com/watch?v=2jW2iSKDipY > > For the scenario you picture on your example, you are right you can not do > join queries. A workaround would be to de-normalize your data model to have > the department information within the employee entity, so you could make a > query over the kind employee. > > Hope this helps you getting started on Datastore and App engine. If you > have more questions don't hesitate to ask! > > Happy coding! > > Best, > Jose Montes de Oca > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/google-appengine/-/-MPXy0Q40QsJ. > > 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 at > http://groups.google.com/group/google-appengine?hl=en. > -- You received this message because you are subscribed to the Google Groups "Google App Engine" 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 at http://groups.google.com/group/google-appengine?hl=en.
