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From Jörg von Frantzius <joerg.von.frantz...@artnology.com>
Subject Re: Feature proposal for JDO 2.1 maintenance: current DB time
Date Thu, 19 Oct 2006 16:02:46 GMT
Hi Craig,

I'm not so sure whether this is really what you want to see, but here's 
something:

    Query query = newQuery("new Date()");
    query.setResultClass(java.sql.Timestamp.class);
    query.setUnique(true);
    Date result = (Date)timeQuery.execute();
      

That result Date can then be used to e.g. set an updated object's 
lastModification timestamp before committing it.

Regards,
Jörg

Craig L Russell schrieb:
> 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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