I'd add "reference_count" property (IntegerProperty(default=0)) to
Photo entity, and increment it each time a reference happens. Then,
call Photo.all().order("-reference_count").fetch(100) to get the top
100 most referenced photos.A few additional notes: 1. If you need an accurate reference count number, you need to put the routine (which reads the Photo entity, increment the reference count, and put it back to the database) into a transaction, but it is relatively expensive. I usually don't put it in a transaction unless I absolutely need an accurate number. 2. Making too many put() calls in one HTTP request is not a good idea. I'd suggest to perform non critical operations (such as incrementing reference count) asynchronously using Task Queue. Satoshi On Jan 6, 4:15 pm, Daniel Aguilar <[email protected]> wrote: > 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%2Bunsubscrib > > [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.
