>  class Sequence(db.Model):
>     @staticmethod
>     def next():
>         seq = Sequence()
>         seq.put()
>         id = seq.key().id()
>         seq.delete()
>         return id
>  print Sequence.next()

>  i'm using it in my gap application, and it seems ok.

>  On Apr 28, 10:37 pm, Mahmoud <mahmoud.ar...@gmail.com> wrote:
>  > Why do you need an auto_increment id?

>  > The datastore already generates a globally _unique_ key for each
>  > entity. Uniqueness is assured by choosing a long enough random
>  > alphanumerical string, which makes collisions practically impossible
>  > and eradicates the need for expensive transactions. Moreover, there is
>  > also a unique numerical id, that is locally unique for that entity
>  > type.

>  > As for record/entity counts, numerous posts have suggested storing the
>  > count somewhere in the datastore. However, one would have to update
>  > the count whenever entities are added or deleted. This adds a penalty
>  > to write operations, but makes fetching the count trivial.

>  > -Mahmoud

>  > On Apr 27, 2:10 am, vrypan <vry...@gmail.com> wrote:

>  > > I wrote some code to implement the equivalent of a "unique
>  > > auto_increment index" in datastore (or better, to overcome the lack of
>  > > it).

>  > > You can find the code here:http://vrypan.net/log/2008/04/27/unique-integer-ids-in-google-datastore/

>  > > It looks like it's working, but I'm a Python newbie, so please point
>  > > out any mistakes or performance considerations!