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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: Running a query over multiple Databases?
Date Fri, 16 Mar 2007 17:33:00 GMT
Doing a join across DB's generally doesn't work (although it may  
*appear* to work in simpler cases of matching of FK), as it will  
require Cayenne to do in memory cartesian product processing. So  
you'll have to do it manually.

(actually sounds like an interesting improvement ... although  
probably low priority to me at least)

Andrus


On Mar 16, 2007, at 5:26 PM, Christian Mittendorf wrote:
> Hi!
>
> I've found the mutiple database example on cayennes homepage:
>
> http://cwiki.apache.org/CAY/multiple-databases-example.html
>
> That example is a pretty good resemblance of our current problem.
>
> What we would like to do is to run a single query over both  
> databases, like i.e.
>
> SelectQuery select = new SelectQuery(Person.class);
> Expression expression = ExpressionFactory.matchExp 
> (Person.DEPARTMENT_PROPERTY +
> 	"." + Department.NAME_PROPERTY, "IT Department");
>
> But such a query runs into an exception with the following error  
> message:
>
> Base table or view not found,  message from server: "Table  
> 'foo.bar' doesn't exist"
>
> Are such queries supported by Cayenne or do we have to split the  
> task into
> two single queries?
>
> Christian
>


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