I use this code to keep an id:
class M(db.Model):
id = db.IntegerProperty()
time = db.DateTimeProperty(auto_now_add=True)
@staticmethod
def max_id():
maxID = memcache.get('MaxID')
if maxID:
return maxID
messages = Message.all()
messages.order("-id")
message = messages.get()
if message:
return message.id
else:
return 0
entity = M()
entity.id = M.maxID + 1
entity.put()
2009/4/19 David Wilson <david.wil...@entertainmentcloud.com>
>
>
> thanks! i missed that in the docs :)
>
> I wasnt using a datetime just to save a bit of space, but i can see i
> need to know to guarantee ordering, or if i want to do ordered paging
> via key i would need to handle key creation myself to make sure they
> are in order.
>
> This becomes harder in one case for me as users can create designs
> that need to be paged through in creation order. There will be too
> much contention on a glodal counter for this, so i guess an offset
> page on date is the best i can do for now. Or just not worry when some
> 'new designs' are out of order.
>
>
>
> On Apr 18, 2:20 am, David Symonds <dsymo...@gmail.com> wrote:
> > On Sat, Apr 18, 2009 at 3:21 PM, David Wilson
> >
> > <david.wil...@entertainmentcloud.com> wrote:
> > > Is this expected behaviour? and thus do i need to always give a
> > > key_name to guarantee order? this creates scaling issues for order
> > > counter (which is probably why its not in order in the backend :) )
> >
> > Keys are only guaranteed to be unique, not sequential or in order:
> > http://code.google.com/appengine/docs/python/datastore/keysandentityg.
> ..
> >
> > What is wrong with giving your models a timestamp property (with
> > auto_now_add=True), and sorting by that?
> >
> > Dave.
> >
>
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