The datastore has no aggregation functions. To get that type of summary data you will want to precompute it.
Robert On Wed, Jan 6, 2010 at 7:15 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]. >> 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. > >
-- 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.
