2010/10/11 Jaganathan (ஜ௧நாதன்) <[email protected]>

> Hi
>
> In my app, I am using auto generated numeric ids. But for every new object
> they ids are stepping thru with a lot of gaps.
>
> Note that all the entities are root entities.
>
> With such stepping, I am really afraid of how many objects I can have at
> max per entity. Also, for many entities, the key id starts from very large
> number rather than 1001.
>
> Here is a sample data, for each entity type:
>
> *Note*: 1001, 4002, 5002, 6003, 9001, 9002, 9004, 13001, ...., 700002,
> 706002, 708002, 711001, 712001, 720001, 725001
> *Node*: 2001, 4005, 5005, 6002, 8002, ....., 690002, 696001, 696003,
> 697004, 699003, 723001
> *NoatUser*: 3001, 9005, 16002, 26001, 26002, 30002, ....., 601002, 601006,
> 603002, 620001, 622001, 706001
> *Feedback*: 360006, 387007, 390006, 391003, 400007, 427002, 429001, 726001
> *FeatureVoteUserDetails*: 325020, 327035, 454011, 454012, 455008, 466010,
> 485015, 491013, 495011, 497007
>
> Questions / Doubts:
>
>  1. Is this much gap in entity id assignments fine and acceptable in App
>> Engine?
>>
>
>

Yes. IDs are guaranteed to be unique, not sequential or contiguous.


>
>>
>>> 2. As numeric id is of 64 bits, one the id hits the limit of 2^64 (or
>>> 2^63 ??), will App Engine cycle back from the beginning, this time using the
>>> left over ids that it stepped thru??
>>>
>>
>>
>

If you generate or skip over a hundred million IDs per second, it will take
you nearly 6000 years to consume all 2^64 available IDs. Let us know when
you're getting close and we'll take care of it. ;)

-Nick Johnson



> 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

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