It's not that GAE doesn't do joins - it's that GAE doesn't do joins for you. You are the query planner.
Your examples seem straightforward: Use two steps. Look up the User by twittername, then get all Attendances associated with the User. You may want to memcache the mapping of twittername to User. This is pretty much exactly what a SQL engine would do if you typed "SELECT a.* FROM Attendance a, User u WHERE u.twittername = ? and u.id = a.userId" The hard problems come when you want to do the kinds of joins that require in-memory hashing or sorting. These are also the kinds of problems that destroy RDBMS scalability, so they're hard no matter what tools you use. Jeff On Wed, Jul 7, 2010 at 11:46 AM, MArtin Schumacher <martin.s.schumac...@googlemail.com> wrote: > Hi John, > > sorry for the delay. > >> You might want to check out Twig which allows direct references for >> both owned and unowned relationships. No Keys required. >> >> http://code.google.com/p/twig-persist/ > > Great. It seams like Twig is exactly what I looked for. Just I cannot > see how I can do joins. > > i.e. in my model mentioned above, I want to select a Person with some > specific ContactData. > > Or I want to find all Attendances for a User logged in with a specific > Twittername. > > Do you have any further hints for me? > > Martin > > -- > 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. > > -- 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.
