To efficiently perform a join in 2 steps, do a db.Query(), then use a batch db.get():
http://code.google.com/appengine/docs/python/datastore/functions.html Robin On Feb 6, 2:07 pm, "Eddeh!" <edval...@gmail.com> wrote: > Hi, > > I'm having trouble implementing a certain table design in GAE. > Consider the following Model: > > class Group(db.Model): > name = db.StringProperty() > description = db.TextProperty() > password = db.StringProperty() > creator = db.ReferenceProperty(User) > created = db.DateTimeProperty(auto_now=True) > > class GroupMembers(db.Model): > user = db.ReferenceProperty(User) > group = db.ReferenceProperty(Group) > admin = db.BooleanProperty() > > class Event(db.Model): > date = db.DateTimeProperty(required=True) > creator = db.ReferenceProperty(User) > group = db.ReferenceProperty(Group) > location = db.StringProperty(required=True) > title = db.StringProperty(required=True) > duration = db.IntegerProperty() > > Now say I wanted to list all events for all the groups which the user > belongs to. Normally this would be easily solved in SQL: > SELECT e.* > FROM GroupMembers gm, Event e > WHERE gm.group = e.group > AND gm.user = <some_user_id> > > Of course I could get a list of group memberships for a user in one > call, then loop through these groups, get all events for each and > combine in a final list. But that is an ugly way of doing it and would > result in 1 + (N memberships) calls to datastore. Is there any clean > way of solving this in GAE? > > Thank you --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
