I would just add one short comment to this and that is there are other good reasons to use an entity group besides the transaction support. First, the parent child relationship can be a powerful construct from a design perspective. Second, queries "within" an entity group will tend to be fast as I understand it as entities in an entity group are stored "close together".
On Jan 11, 11:32 pm, Julian Namaro <[email protected]> wrote: > Your model won't work if one message can have several recipients. Is > this OK? > And is there a particular reason why you create an entity group for a > user and its messages ? > You only need an entity group if you plan to update different entities > transactionally. > > Also, you might be interested by this parallel > thread:http://groups.google.com/group/google-appengine/browse_thread/thread/... > > On Jan 10, 3:27 am, "sameer.mhatre" <[email protected]> wrote: > > > I need suggestion for the database model designed by me for the app I > > am going to develop. > > > Requirement: > > I am going to fetch messages (belongs to a particular user) and insert > > into the datastore and update the unread count for that user > > accordingly. Later on user can do operations like marking all/some > > read/unread to his/her own messages. > > > Database Model: > > Entities: User, Message, Count > > Entity Group: list of messages (belongs to a single user) and count > > (to keep trac of read/unread) entity. Entity group is per user > > specific (kept user's email id as parent for the entities to keep them > > in a single group). > > > Operations: > > Insert: I want to add list of messages by making a makePersistsAll > > method call and update count for a user accordingly. I think I have to > > do this in a single transaction. Messages to be added belongs to a > > entity group (means belongs to a single user). > > Update: Updating status for the list of messages (could be more than > > 1000 entities) and update Count accordingly. Again doing it in a > > single transaction. Messages to be updated belongs to a single entity > > group (means belongs to a single user). > > > May be possible that more than one user's requests comes in and have > > to add/update entity groups per user simultaneously. > > > Is there any problem with this design model? Anything you can suggest > > to me. > > > Thanks > > Sameer -- 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.
