Hi Nick,
On Tue, Aug 11, 2009 at 7:50 PM, Nick Johnson
(Google)<[email protected]> wrote:
>
> On Tue, Aug 11, 2009 at 7:29 AM, Takashi Matsuo<[email protected]>
> wrote:
>>
>> Hi Nick,
>>
>> On Thu, Jul 30, 2009 at 4:48 PM, Nick Johnson
>> (Google)<[email protected]> wrote:
>>> Hi Takashi,
>>>
>>> If the entity being put has neither key name nor id, a new id will be
>>> created for it when it's put, so it will always result in a new entity being
>>> inserted rather than an existing entity being replaced. Likewise, if you see
>>> an entity with an id being put, it is almost certainly an update to an
>>> existing entity (unless someone was messing around with the low-level API),
>>> or the entity was deleted and is now being reinserted.
>>>
>>> If the entity being put has a key name, the only way to tell for certain if
>>> it's replacing an existing entity is to do the put operation in a
>>> transaction, and do a get on the key first.
>>
>> Thank you for clarification. Here comes another question.
>> Is there any way to tell if particular PUT operation is in a
>> transaction or not, and
>> tell if the transaction is committed or rollbacked?
>>
>> I'd like to add a capability for adding arbitrary callback that will
>> be executed only when entities are actually put (that won't be
>> executed when the put operation is rollback-ed).
>
> You probably want to look into the datastore's support for hooks:
> http://code.google.com/appengine/articles/hooks.html
Thanks for your suggestion, but I've already read this article. In
case I've missed something, I read it again carefully, but what I want
to know is not written in the article.
I should have explain my question more precise and concretely.
OK, here is pseudo codes I'm working on.
---------------------------------------------------------------------------------
def db_hook(service, call, request, response):
if call == 'Put':
from kay.utils.db_hook import execute_hooks
for key, entity in zip(response.key_list(), request.entity_list()):
kind = model_name_from_key(key)
execute_hooks(kind, key, entity)
apiproxy_stub_map.apiproxy.GetPostCallHooks().Append(
'db_hook', db_hook, 'datastore_v3')
----------------------------------------------------------------------------------
When I tested with dev_appserver, this execute_hooks function was
invoked even if the transaction that contains this PUT operation, was
rollbacked.
I want to invoke execute_hooks function only when this PUT operation
is committed.
Is there any way to do that?
-- Takashi
> -Nick Johnson
>
>>
>> --- Takashi
>>
>>> -Nick Johnson
>>>
>>> On Thu, Jul 30, 2009 at 7:19 AM, Takashi Matsuo <[email protected]>
>>> wrote:
>>>>
>>>> Hi,
>>>>
>>>> I'm writing a capability for registering db_hook dynamically. The code
>>>> snippet follows the mail body.
>>>> It works well except my code can not distinguish newly created entity
>>>> from updated entity.
>>>>
>>>> I'd like to know how can I know if the entity is created or just
>>>> updated. What is the most appropriate way?
>>>>
>>>> Regards,
>>>>
>>>>
>>>> ------------------------------------------------------------------------------------------
>>>> from google.appengine.api import apiproxy_stub_map
>>>> from google.appengine.api import datastore
>>>> from google.appengine.ext import db
>>>>
>>>> post_save_hooks = {}
>>>>
>>>> def register_post_save_hook(func, model):
>>>> global post_save_hooks
>>>> kind = model.kind()
>>>> func_list = post_save_hooks.get(kind, None)
>>>> if func_list is None:
>>>> func_list = []
>>>> func_list.append(func)
>>>> post_save_hooks[kind] = func_list
>>>>
>>>>
>>>> def execute_hooks(kind, key, entity):
>>>> func_list = post_save_hooks.get(kind, None)
>>>> if func_list is not None:
>>>> entity.key_.CopyFrom(key)
>>>> e = datastore.Entity._FromPb(entity)
>>>> instance = db.class_for_kind(kind).from_entity(e)
>>>> for func in func_list:
>>>> func(instance)
>>>>
>>>> def db_hook(service, call, request, response):
>>>> if call == 'Put':
>>>> from kay.utils.db_hook import execute_hooks
>>>> for key, entity in zip(response.key_list(), request.entity_list()):
>>>> kind = model_name_from_key(key)
>>>> execute_hooks(kind, key, entity)
>>>>
>>>> apiproxy_stub_map.apiproxy.GetPostCallHooks().Append(
>>>> 'db_hook', db_hook, 'datastore_v3')
>>>>
>>>> ------------------------------------------------------------------------------------------
>>>>
>>>> --
>>>> Takashi Matsuo
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Nick Johnson, Developer Programs Engineer, App Engine
>>>
>>> >
>>>
>>
>> >
>>
>
>
>
> --
> Nick Johnson, Developer Programs Engineer, App Engine
>
> >
>
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