Hi Nick and others
Finally, I tried my app on the imported DB today. The import was done as per
the technique mentioned in the previous mail.
As expected, it threw the following error, when I initiated an action that
creates a new entity:
*the id allocated for a new entity was already in use, please try
again*Traceback (most recent call last):
[some trace truncated]
File
"/base/data/home/apps/notesonatree/1-5.344881683710780408/notesonatree/core/models.py",
line 111, in create_note
new_note.put()
File
"/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py",
line 893, in put
return datastore.Put(self._entity, rpc=rpc)
File
"/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py",
line 293, in Put
raise _ToDatastoreError(err)
InternalError: the id allocated for a new entity was already in use,
please try again
:D . Is there a way to work around this? Is this a work in progress?
Also try to answer my previous mail if possible.
Thanks
Jagan
2010/9/13 Jaganathan (ஜ௧நாதன்) <[email protected]>
> Hi Nick and others
>
> Thank you for your response.
>
> More inline below ...
>
> On Thu, Sep 2, 2010 at 8:17 PM, Nick Johnson (Google) <
> [email protected]> wrote:
>
>> Hi Jagan,
>>
>> On Tue, Aug 31, 2010 at 9:46 AM, Jagan <[email protected]> wrote:
>>
>>> Hi Google, Nick Johnson and others
>>>
>>> Does Google recommend using UUID (UUID4 to be specific) as key names
>>> for entities in GAE instead of auto generated numeric ids?
>>>
>>> Does this hold good in all use cases in the universe?
>>>
>>
>> This depends entirely on your use-case. Unless you expect an extremely
>> high insertion rate of new entities (eg, >=100QPS) with no natural key name,
>> it's not necessary to use a UUID. UUIDs take more space than regular integer
>> IDs.
>>
>>
>>>
>>> And is this the reason why import export of auto generates IDs are not
>>> yet supported in BulkUpload? Should I wait till this is supported or
>>> should I refactor my code to use UUID key names?
>>>
>>
>> It's possible to do this using the bulkloader, but requires you to
>> override a method to generate key names.
>>
>
> Were you speaking about the old bulkloader? From looking at the code
> at<sdk-home>\
> google\appengine\tools\bulkloader.py, I think that might not work, because
> even if we return a Key constructed with the id, it is later doing
> loader.create_entity with the key name. Here is the snippet that I am
> relating to:
>
> Line 1260-1267:
> for line_number, values in rows:
> key = loader.generate_key(line_number, values)
> if isinstance(key, datastore.Key):
> parent = key.parent()
> key = key.name()
> else:
> parent = None
> entity = loader.create_entity(values, key_name=key, parent=parent)
>
>
> Anyways, I tried the following technique in the new bulkloader:
>
> - kind: XYZ
> connector: csv
> connector_options:
> property_map:
> - property: __key__
> external_name: key
> *import_transform: transform.create_foreign_key('XYZ', True)*
> export_transform: transform.key_id_or_name_as_string
>
> It is working. Is this good enough?
>
> But* *I have one general doubt here. I read in one forum that, with these
> techniques, the *sequence number* (?) that GAE maintains for the next new
> generated id wont be incremented / updated, and so when our app tries
> to create a new entity, its auto generated id might clash. Is this true? Is
> there any link that describes how auto increment ids work on App Engine?
>
>
>>
>>
>>>
>>> Is there a demo page that compares between the bulk read/write
>>> performance between entities that have 32-bit numeric ids versus xxx-
>>> bit UUID key names?
>>>
>>
>> The performance should be roughly the same - but the space used will be
>> significantly larger in the case of UUIDs.
>>
>> -Nick Johnson
>>
>>
>>>
>>> Some home work that I did:
>>>
>>>
>>> http://groups.google.com/group/google-appengine/browse_thread/thread/bc868376ffa37619/db9bda21c95ea806?lnk=gst&q=uuid#db9bda21c95ea806
>>>
>>>
>>> http://groups.google.com/group/google-appengine/browse_thread/thread/a6fcce84837c34b/d4c9d5b3c7869222?lnk=gst&q=uuid#d4c9d5b3c7869222
>>>
>>>
>>> http://groups.google.com/group/google-appengine/browse_thread/thread/7dedb7d65bdf4f/37f2733fd9f572b9?lnk=gst&q=uuid#37f2733fd9f572b9
>>>
>>> Thanks
>>> Jagan
>>>
>>> --
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>>>
>>>
>>
>>
>> --
>> Nick Johnson, Developer Programs Engineer, App Engine Google Ireland Ltd.
>> :: Registered in Dublin, Ireland, Registration Number: 368047
>> Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration Number:
>> 368047
>>
>
> Thanks
> Jagan
>
> --
> Let the words of our mouth and the meditations of our heart
> Be acceptable in Thy sight here tonight!
> - Rivers of Babylon (album)
>
--
Let the words of our mouth and the meditations of our heart
Be acceptable in Thy sight here tonight!
- Rivers of Babylon (album)
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