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From Craig Russell <Craig.Russ...@Sun.COM>
Subject Re: Interpretation of fetch depth
Date Wed, 31 Aug 2005 18:14:21 GMT
Hi Jörg,

The fields to be fetched from the instance(s) reachable from this  
field are governed by the fetch plan in effect. That is, the fetch  
groups in the fetch plan are used to determine the set of fields to  
be fetched. So all of the primitive fields in the fetch groups would  
be fetched (and none of the relationship fields, as you pointed out).

If you want only the primary key to be fetched, then you should  
specify fetch groups in your fetch plan that do not include "default"  
and don't include any of the other fields in the reached class.



On Aug 31, 2005, at 10:47 AM, Jörg von Frantzius wrote:

> Hi,
> in the spec, in §12.7.2 it reads
>    "Recursive fetch group references are controlled by the fetch-depth
>    attribute. A fetch-depth of 0 will fetch the whole graph of
>    instances reachable from this field. The default is 1, meaning that
>    only the instance directly reachable from this field is fetched."
> For a fetch-depth of 1, when we fetch such a reachable instance,  
> what fields of that instance should be fetched exactly? All I know  
> is we must not fetch any of its object fields, as recursion stops  
> here. One solution would be to fetch only the primary key, would  
> that be in the sense of the specification? It might seem strange,  
> but for my application this makes the most sense.
> Regards,
> Jörg
> -- 
> __________________________________________________________
> Dipl.-Inf. Jörg von Frantzius  |            artnology GmbH
>                               |                Milastr. 4
> Tel +49 (0)30 4435 099 26      |              10437 Berlin
> Fax +49 (0)30 4435 099 99      |  http://www.artnology.com
> _______________________________|__________________________

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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