> The decision to allow setting key_names but not IDs is something we may > revisit.
I hope that you're also considering some way to request and allocate an unused id for a given path prefix. (That way we can get unique key ids to specify.) On Jun 15, 4:45 pm, "Jeff S (Google)" <j...@google.com> wrote: > Hi cryb, > > As you noted, we do not currently allow the ID for a key to be set, as we > ensure that the ID is unique for each existing entity. I recommend using a > key name instead of an ID, as Antoniov suggeted, if possible. > > It is technically possible to modify the key of an entity as it is being > converted to a protocol buffer message before it is sent to the datastore. > You could do this using hooks in the API proxy as described in this > article:http://code.google.com/appengine/articles/hooks.htmlAlso it is > possible to > construct the key for the desired object if you know the ID in advance. > > class X(db.Model): > pass > > # If you've already created the entity so you have the ID. > x_id = X().put().id() > > # Instead of getting by ID, you can create the key manually. > k = db.Key.from_path('X', x_id) > > Now you have the desired key without having fetched the object, but the part > which the model class does not allow is setting the key yourself. So you > could modify the protocol buffer message before it is written to the > datastore, but I don't recommend it. > > The decision to allow setting key_names but not IDs is something we may > revisit. > > Happy coding, > > Jeff > > 2009/6/12 cryb <cbuti...@gmail.com> > > > > > > > Hi.. that is to build key names... What I asked was why I can't build > > a key ID.. > > > On Jun 12, 5:35 am, Antoniov <nio....@gmail.com> wrote: > > > Use the code: > > > s = Story(key_name="xzy123") > > > Then you create an entity with the key name "xzy123". > > > > Check this: > >http://code.google.com/intl/en-US/appengine/docs/python/datastore/key... > > > > On 6月12日, 上午1时28分, cryb <cbuti...@gmail.com> wrote: > > > > > Does anyone know why it is possible to build a key name but NOT a key > > > > id? I know key IDs are used as autoincrements, but why can't I just > > > > override this mechanism and build my own key id? > > > > Suppose I want to overwrite an existent entry in my table that has a > > > > key id I know, and also I want to keep that key id after update... > > > > because I can't just build a key id, I am forced to fetch that entity, > > > > modify it and write it back, instead of just write the updated entity > > > > with the key id I already know - so an additional read to the > > > > datastore. > > > > Is there an obscure reason for that? (both key names and key ids are > > > > prefixed with appid/kind as far as I know so there is no chance of > > > > collision with other apps/kinds)- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
