Hi You might like to say if you are using python or java, that way examples can be relevent to your choice.
> > DOUBT 1: What happens, if i make a change to the User class and, for > example, i add to the class the property sex (String). Then i deploy > my app again in the appengine. > > Now i create a new user with this values username = "mcculloch", > password = "mc123" and sex = "M" and persist the user. > > I think that if i make the query to get all the useri will get the 2 > users, and the property sex to the user "ian" will be null. Is that > correct? Yes. > > DOUBT 2: Now i realize that i don't want to store the sex of the user, > and also i think that i don't want the id property as an integer. Now > i want that the username will be the key of the class, so i remove the > id property and add the annotation to make the username property the > Primary Key of the entity. > > Then i deploy the app on appengine, create a new user with this > values: username = "eric", password = "eric123". > > What does happen now i query all the users, will i get the two users? > Ok a bunch of stuff going on here. You refer to the primary key, do you mean as per SQL or some aspect of a java api. In the underlying datastore terms the key of entity once created is fixed. You would have to copy the original entity and delete the old one to change the key. As to the sex property. (I will start using python behaviour) you can drop the sex property definition from the entity but the value assigned to the Sex property will still exist in entities that had the value set. If you change the type of a property then you will need to fetch the old entity and update the value of the property to the type the model expects. This may require you to manipulate the underlying raw datastore entity or create a transition class to help you migrate the schema (i prefer the former). if not you will get errors when you retrieve entities with a mis- matched entity definition. If you fetch all uses User.all().fetch(n) you will get all users added assuming you have fixed above. > DOUBT 3: Let's say that i realize that i really need the sex property > for the users, so i add again the sex property to the User class and > deploy again to the datastore. > > If i query for all the users? What datastore will return to me? All > the users? Only those that the sex is not null? All users will be returned, and some will still have a value for sex. You can't do a not null query unless you have actually stored None (python) in a property. (More specifically you can't query for entities that have not had a property value set). > > DOUBT 4: Finally, what happens if i want to have 2 enviroments of my > app? I have to create 2 apps on appengine? If this is the way, let's > supose that in my production enviroment i have a lot of data and i > want to make a copy of that data to my testing app so i can make > testing with good data. Can i copy that data from one app to another? > How could i? See http://code.google.com/appengine/docs/python/tools/uploadingdata.html T -- 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-appeng...@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.
