Can't get no (Transformer)

[Diogo FC Patrao]

Hi all,

I'm having trouble figuring out how Transformer class is working. See my
classes below:


public class GrumpyOptimizer extends TransformCopy {

@Override
 public Op transform(OpUnion opUnion, Op left, Op right) {
 if ( !( left instanceof OpService && right instanceof OpService))
 return opUnion;
 Node l = ((OpService)left).getService();
Node r = ((OpService)right).getService();

// both runs go inside this if
 if (l.toString().compareToIgnoreCase(r.toString()) > 0 ) {
return new OpUnion( right, left );
 }
return opUnion;
 }

}

// --- test

 GrumpyOptimizer go = new GrumpyOptimizer();

 System.out.println("Teste 1");

  Query query = QueryFactory.create("SELECT ?a {" +

//** "{ SERVICE <http://3.com/> { ?a <
http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://marafo.com/teste>
} }" +

//** "UNION " +

  "{ SERVICE <http://2.com/> { ?a <
http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://marafo.com/teste>
} }" +

  "UNION " +

  "{ SERVICE <http://1.com/> { ?a <
http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://marafo.com/chatuba>
} } }" );


 Op op = Algebra.compile(query);

 System.out.println(op);

  op = Transformer.transform(go, op);

 System.out.println(op);

Ok; when running the code above keeping the commented lines, I get the
expected result below:

Teste optimizer
(project (?a)
  (union
    (service <http://2.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>)))
    (service <http://1.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/chatuba>)))))

(project (?a)
  (union
    (service <http://1.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/chatuba>)))
    (service <http://2.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>)))))


It "orders" the services by endpoint URL; however, If I uncomment the lines
marked with //**, nothing changes:

Teste optimizer
(project (?a)
  (union
    (union
      (service <http://3.com/>
        (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>)))
      (service <http://2.com/>
        (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>))))
    (service <http://1.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/chatuba>)))))

(project (?a)
  (union
    (union
      (service <http://3.com/>
        (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>)))
      (service <http://2.com/>
        (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/teste>))))
    (service <http://1.com/>
      (bgp (triple ?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
http://marafo.com/chatuba>)))))

I wasn't expecting that the whole thing would be sorted, but at least the
first two OpService should. In case you're wondering, it gets into the IF
that flip the nodes in both cases.

It's running JENA 2.10.1-SNAPSHOT (apr-4).

Thanks in advance!

--
diogo patrão