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From Craig L Russell <Craig.Russ...@Sun.COM>
Subject [IMPORTANT] Fetch-depth
Date Fri, 13 Jan 2006 23:10:19 GMT

I've spent some time looking at the semantics of fetch-depth and now  
agree with the critics of the change that I proposed back in the  
infamous October 1, 2005 message to the expert group subject: Re:  
JDO2 ยง12.7.2: fetch-depth only for "recursive fetch group references"?.

I now believe it's impractical to use fetch-depth to mean the maximum  
depth of the object graph reachable from the root object(s) field  
because of several messages sent on the subject by Joerg von  
Frantzuis, Alexander Bieber, and Marco Schultz.

Briefly, the argument is that if fetch-depth limits the number  
absolutely, then it's not possible easily to use the fetch-group to  
add another field to a fetch plan simply by adding a fetch-group that  
includes that field. Instead, a new fetch-group that changes the  
fetch-depth must be used. And each new use-case needs to provide a  
different fetch-depth number if another level of fetching is desired.

I believe that the use of fetch-group to determine whether fields  
(navigating relationships) are fetched should be natural, and that we  
should therefore use fetch-depth for its original purpose of limiting  

If you disagree with this position, please reply so we can move  
forward and define the use of fetch-depth for recursion (as in the  
original semantics of the attribute).



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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