On Wed, Mar 9, 2011 at 1:21 AM, Emmanuel Bernard <emmanuel.bernard_at_jboss.com
> wrote:
>
> On 7 mars 2011, at 21:45, Linda DeMichiel wrote:
>
> > SELECT e FROM Employee JOIN e.projects p
> > WHERE TREAT(p AS LargeProject).budget > 1000 OR
> > TREAT(p AS SmallProject).name LIKE "Persist%" OR
> > p.description LIKE "COST OVERRUN"
>
> This is really the use case that makes the most sense to me as the other
> use cases Linda has shown seem to overlap with TYPE.
>
> but that leads to some questions:
> 1. if both LargeProject and SmallProject have a budget property, do we
> return all Projects.budget > 1000? Or is the query more like
> SELECT e FROM Employee JOIN e.projects p
> WHERE ( TYPE(p) = LargeProject AND p.budget > 1000) OR
> (TYPE(p) = SmallProject AND p.name LIKE "Persist%" ) OR
> p.description LIKE "COST OVERRUN"
>
> For reference the idiom in Java is
> (p instanceof LargeProject && ( (LargeProject) p).projects > 1000) ||
> (p instanceof SmallProject && isLike( ((SmallProject) p).name, "Persist%"
> ) ) ||
> isLike(p.description, "COST OVERRUN") //evaluates to true all the time?
>
> And assuming javac was smarter we could do
>
> (p instanceof LargeProject) && p.projects > 1000) ||
> (p instanceof SmallProject) && isLike( p.name, "Persist%" ) ||
> isLike(p.description, "COST OVERRUN")
>
> 2. if LargeProject does not have a budget property, what happens?
>
>
>
I suppose, if LargeProject does not have a budget property an exception
would have to be thrown in any case.
Although you may as in the Java examples get a simple true/false result,
most cases in Java where you'd try to directly compare or cast two types
into each other would also result in a (ClassCast)Exception.
Werner