Here are some stats:

http://bthomson-test-app.appspot.com/ancestor_tests

create and put 50 models using db.put(models)
  Billable API CPU time: 2900 mcycles

get 50 models using db.get(keys)
  Billable API CPU time: 500 mcycles

delete 50 models using db.delete(keys)
  Billable API CPU time: 1250 mcycles

On Feb 20, 7:41 am, kang <[email protected]> wrote:
> Hi peterk, maybe the delete() operation uses the most CPUs  :) Anyway, I
> will have a test, thanks
>
>
>
>
>
> On Sat, Feb 20, 2010 at 8:16 PM, peterk <[email protected]> wrote:
> > I've never tested this, but is it possible you'd see better 'per-
> > delete' cost with a larger batch?
>
> > Maybe try the maximum number of entities in a batch (500, I think),
> > calculate the average cost per entity, and see if that's any better?
>
> > On Feb 20, 11:41 am, kang <[email protected]> wrote:
> > > Thanks, Andrew. But after the change, it still costs me 2130cpu_ms
> > > 2112api_cpu_ms :)
>
> > > On Sat, Feb 20, 2010 at 5:22 PM, Andrew Chilton <[email protected]
> > >wrote:
>
> > > > On 20 February 2010 21:21, kang <[email protected]> wrote:
> > > > > I'm going to clear the datastore. I use the following code:
> > > > >     old_date = datetime.datetime(2009,10,1)
> > > > >     old_updates = SomeUpdate.all().filter("updated
> > <",old_date).fetch(20)
> > > > >     db.delete(old_updates)
> > > > > it costs me nearly 1982cpu_ms 1945api_cpu_ms every time. Is it
> > normal?
>
> > > > You might be able to save some time by using a keys_only query. See
> > > > this for details.
>
> > > >http://code.google.com/appengine/docs/python/datastore/modelclass.htm.
> > ..
>
> > > > Cheers,
> > > > Andy
>
> > > > --
> > > > contact: Andrew Chilton
> > > > website:http://www.chilts.org/blog/
>
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