Hi Craig,
I agree the BNF would allow the query.
As I understood, the offending part is the aggregate on an expression
ending in a size method call, correct? Then, the problem is not related
to subqueries and we have it in JDO 2.0 already:
select max(this.children.size()) from x.y.Node
Do we need to restrict the use of method calls inside of aggregate
expressions to better support mapping JDOQL -> SQL?
Regards Michael
Hi Christiaan,
As I read the BNF for this filter, there's nothing to prevent it.
But you are right that it might be difficult if not impossible to
translate this into SQL. Have you tried it with your favorite database
or JDO implementation?
Craig
On Feb 21, 2008, at 7:14 AM, Christiaan wrote:
Hi,
a question about subqueries. With the subquery spec, should it be
possible
to execute the following filter, which should return the nodes with the
maximum children?
"children.size() == (select max(node.children.size()) from x.y.Node
node)"
I am asking this since the size() is probably translated into a
count() and
I don't believe it is allowed to perform an aggregate on another
aggregate
in sql.
regards,
Christiaan
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Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
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