You could do an entity that has 50 genre counters. Some thoughts:
1) It seems like you can make genre part of a list property in a CD since each CD will only be a small number of genres. 2) I wouldn't use a Reference List for a User entity, because a User might have thousands of CDs. See Rafe Kaplan's article on modeling entity relationships (http://code.google.com/appengine/articles/ modeling.html). I'd model the User <-> CD relationship with a separate Ownership entity that has key references to a CD and User entity. You could add additional info into this relationship model, like whether the Owned CD has been lent to another User. 3) Are genres fixed or user-configurable (like a "tag" instead of a universal genre)? If they are like tags and user-configurable, you could but the genre list in each Ownership entity. Then if User X wants to know how many "1980s Top Hits" he owns, you could query the Ownership entities. You could then memcache the (User, Genre, #CDs for genre) tuple instead of keeping 50 counters in User and just query again if needed. -Bill On Jan 15, 2:23 am, Chen Harel <chook.ha...@gmail.com> wrote: > Hi, In case I want to represent a music album datastore, > I wish the user can add a cd that he likes (no need for information > other than cd name and genres) > Now, at first I looked at it as a RDBMS even in BigTable, meaning I > had > User entity > CD entity > Genre entity > With list of refrences keys... > Now after playing with it, I realized (at least I think so) that I am > killing my application, > Since I need to be able to supply the aggregations on "how many R&B > cd's user XXX has" > this query can't be optimized (at least with my current knowledge) on > BigTable, > So I need to start putting up counters... but I am questioning you > about the number of properties allowed (or make sense) > If I support 50 genres, can I simply do an entity that has: > User: > id > name > cds (list of refrences) > total_cd_counter > trance_cd_counter > house_cd_counter > rnb_cd_counter > .. (47 more counters) > > And when I add / remove a cd for a user, I shall update the > appropriate counter ... > This will make query for the favorite genre (which is the main goal :) > - Sorry I got to it only here) of the application... > > Please tell me if this will work, and will have sufficient > performance / scaling capabilities... --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
