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From Craig L Russell <Craig.Russ...@Sun.COM>
Subject Re: Feature proposal for JDO 2.1 maintenance: current DB time
Date Thu, 19 Oct 2006 15:36:58 GMT
Hi Jörg,

Sorry to exercise you more on this, but I'm still having a bit of  
difficulty seeing how to use this feature.

Could you please give us an example of the use case you describe  
below? I'd like to see the JDOQL query that uses new Date() in action.

Thanks!

Craig

On Oct 19, 2006, at 1:33 AM, Jörg von Frantzius wrote:

> Hello Craig,
>
> as far as I can see that does satisfy our requirements. Once we are  
> able to query for that date in JDOQL, we can use it e.g. for  
> lastmodification timestamps and the like.
>
> Regards,
> Jörg
>
> Craig L Russell schrieb:
>> It's easy enough to define "new Date()" as being evaluated on the  
>> back end for queries that are executed on the back end. And being  
>> evaluated in the vm for queries that have a bound  
>> candidateCollection.
>>
>> But does this satisfy the requirements? Once you have a Date in  
>> JDOQL, what can you do with it?
>>
>> Craig
>>
>> On Oct 16, 2006, at 11:58 AM, Erik Bengtson wrote:
>>
>>> +1. maybe "new Date()" could be the expression where evaluation  
>>> occurs on the
>>> database.
>>>
>>> Quoting Jörg von Frantzius <joerg.von.frantzius@artnology.com>:
>>>
>>>> Dear experts,
>>>>
>>>> there had been several occasions where in our applications we  
>>>> had to
>>>> determine the database server's current time(-stamp). In one  
>>>> application
>>>> we needed it to synchronize sent JMS messages with visibility of  
>>>> commits
>>>> in the database, and in another we need it for our simple  
>>>> replication
>>>> algorithm.
>>>>
>>>> In distributed systems in general it is often crucial for
>>>> synchronization purposes to have a common source of time  
>>>> information
>>>> that is accessible from all processes.
>>>>
>>>> It would be great if JDO2 could offer a way of doing that  
>>>> independently
>>>> of the database, e.g. as a JDOQL function.
>>>>
>>>>
>>>> Regards,
>>>> Jörg
>>>>
>>>
>>>
>>>
>>
>> Craig Russell
>> Architect, Sun Java Enterprise System http://java.sun.com/products/ 
>> jdo
>> 408 276-5638 mailto:Craig.Russell@sun.com
>> P.S. A good JDO? O, Gasp!
>>
>

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!


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