Hi Satoshi, thanks for your reply, it really helped. In fact I just read this artile: http://code.google.com/appengine/articles/modeling.html and have started implementing based on it. Still wondering a couple of things, though... for instance, in my app I have another class called Collage. A collage entity has properties like name, date_created, etc... but also layer_0, layer_1 and layer_2, which are references to Photo entities. What kind of query could i perform in order to get the most referenced Photos?
Thanks again! need to keep track of how many times On Thu, Jan 7, 2010 at 12:51 AM, Satoshi <[email protected]> wrote: > First of all, please remember that GAE/database is an Object-database, > not a Relational-database. You can design your database with > relations, but you will likely hit a roadblock later if you heavily > rely on relations (because of the lack of JOIN and the performance > problem of nested queries). > > If I were you, I would simply create two models (Artist and Photo), > and have the "artist" property on Photo class, which is just a > reference to an Artist entity (ReferenceProperty). If you want to > show all the Photos done by a particular Artist, you just need to > query it (Photos.all().filter('artist', ...)). > > Alternatively, you could specify the Artist entity as the parent > entity of each Photo, which essentially creates an entity group for > each Artist - which has pros (transactions) and cons (possible > performance hit because of transactions). > > Third alternative is ListProperty, but this is difficult to do it > right without putting them in an entity group (which is alternative > two)... > > Satoshi > > On Jan 5, 9:52 am, Daniel A <[email protected]> wrote: > > Hi there, > > > > I just started writting my first app after reading some documentation > > and tutorials. > > Looks like an exciting platform to develop on, but there're many > > things I still have doubts about. > > I used to develop in PHP/MySQL, and I quite don't get how should I > > proceed in order to get an efficient relational model. > > > > To simplify things, I have two kind of entities: Artist and Photo. I > > need to define relations one-to-many between instances of these two > > entities. That is, an Artist can have many Photos, and a Photo can > > only have one Artist. > > > > In my table-shaped mind, I would model three kinds of entities > > (Artist, Photo, ArtistPhotoRelation). Would this approach be the right > > thing in GAE/datastore? Maybe I should avoid the relational entity, > > and use multiple-valued properties in the Artist instead? > > > > Thanks a lot! > > -- > 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]<google-appengine%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > > > >--
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