We're hoping to get key-only queries out in the next release.
- Jason
2009/4/26 Alkis Evlogimenos ('Αλκης Ευλογημένος) <[email protected]>
> The sample code does:
> MyModel.all().fetch(1000)
>
> This means fetch 1000 entities of MyModel. If each entity is 10kb this
> means 10MB of data read from datastore, 10MB of data sent through the
> network to your running instance and 10MB of data server from the running
> instance to your machine running the remote script.
>
> If you know the keys then you can do:
>
> db.delete([db.Key.from_path('MyModel', key_name) for key_name in
> one_thousand_key_names])
>
> This just sends the keys to the datastore for deletion. It doesn't need to
> transfer data from the datastore to the remote script to read the keys in
> the first place.
>
> Eventually GAE api should provide us some way of querying the datastore for
> keys only instead of getting entities necessarily. This would make this
> use-case quite a bit faster and a lot of others as well.
>
> 2009/4/26 Devel63 <[email protected]>
>
>
>> Can you explain this further? I don't see any reference to key_name
>> in the sample code.
>>
>> More importantly, to me, what's the cost differential between using
>> string representation of keys and key_names? I've been passing around
>> key_names to the browser because they're shorter, under the assumption
>> that the cost to get the corresponding key on the server side was
>> negligible.
>>
>> On Apr 25, 9:02 am, Alkis Evlogimenos ('Αλκης Ευλογημένος)
>> <[email protected]> wrote:
>> > Doing it over the remote api means you are going to transfer all your
>> data +
>> > transmission overhead over the wire. You are probably better off doing
>> > something like this on the server side through an admin protected
>> handler.
>> >
>> > Also if you happen to know the keys of your data (you used key_name)
>> your
>> > deletes are going to be a lot more efficient if you give db.delete a
>> list of
>> > keys instead.
>> >
>> >
>> >
>> > On Sat, Apr 25, 2009 at 2:41 PM, Sri <[email protected]> wrote:
>> >
>> > > Hi,
>> >
>> > > Is there a way to completely erase the production data store?
>> >
>> > > Currently I am using a script like this via the remote api:
>> >
>> > > def delete_all_objects(obj_class):
>> > > num_del = 300
>> > > while True:
>> > > try:
>> > > objs = obj_class.all().fetch(1000)
>> > > num_objs = len(objs)
>> > > if num_objs == 0:
>> > > return
>> > > print "Deleting %d/%d objects of class %s" % (num_del,
>> > > num_objs, str(obj_class))
>> > > db.delete(objs[:num_del])
>> > > except Timeout:
>> > > print "Timeout error - continuing ..."
>> >
>> > > But with 30000 entities in the data store and another 3 million (yep
>> > > thats right) coming, doing a clear this way is extremely slow.
>> >
>> > > Any ideas?
>> >
>> > > cheers
>> > > Sri
>> >
>> > --
>> >
>> > Alkis
>>
>>
>
>
> --
>
> Alkis
>
> >
>
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