This may help with #2: http://gae-java-persistence.blogspot.com/2009/10/executing-batch-gets.html
However, I think your #3 is actually the tough part, as retrieving Data for each Person in a list of Persons requires multiple queries or an IN clause, but the latter gets executed as separate fetches under the covers in GAE. /dmc http://turbomanage.wordpress.com/ On Dec 22, 3:48 am, Søren Kyndi-Wiuff <so...@sxl.dk> wrote: > Greetings > > I am trying to figure out a best-practice for avoiding the use of > joins. So far, it isn't going too well so here I am asking if anyone > is up for sharing their experience or linking to the reference I > failed to find. :) > > An example of my requirement is this: > > We have two classes: > > Person > ----------- > + listData > + listPerson > > Data > ------------ > + person > > The domain model is not set in stone, but merely to illustrate that a > Person somehow have a list of "Friends" in his listPerson attribute > and that he somehow have a list of his own data in the listData. > > Now, getting the Data for a single Person is trivial. > > But, getting the Data for a Persons friends is not. > > I cannot get around somehow having to: > > 1) Fetch the Person (1 query) > 2) Fetch all Person in listPerson (n queries per friend) > 3) Fetch all Data by the list provided in 2) by combining all the > friends listData fields (1 query) > > The problem is the (n queries) in step 2, which I belive would be a > killer and eventually be a deadend when people have more than 30 > friends. > > Any hints? :) -- 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.
