not performant query

[Zen 98052]

Hi,

I have a Sparql query below, which doesn't seem efficient.

I noticed when running it, Jena calls execute(OpBGP opBGP, QueryIterator ...) 
so many times.

I have my own implementation in that function (overrides base class 
OpExecutor), which it'll make call to our back-end storage.

>From qparse output (attached below), it looks like the culprit is because the 
>query has BGPs inside the FILTER, which explains the behavior I am seeing.


Is there a better way to re-write the query below to achieve same result, but 
more efficient (and lead to better performance)?


Thanks,

Z



/// SPARQL QUERY:


PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX raw: <http://v/raw#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX v: <http://b/dir/>

SELECT (COUNT(?x) AS ?count) WHERE
{
  ?x rdf:type v:Person .
  {
    SELECT ?x WHERE
    {
      ?x v:hasSnapshot ?snapshot .
      ?snapshot rdf:type v:DS .
      ?snapshot v:mdId ?id .
      VALUES ?id { 'b01.xml' 'f5f.xml' }
      MINUS
      {
        ?x v:hasSnapshot ?snapshot .
        ?snapshot rdf:type v:DS .
        ?snapshot v:mdId ?id .
        VALUES ?id { 'def.xml' '191.xml' }
      }
    }
  }
  ?x ?p ?o .
  OPTIONAL
  {
    ?o ?x ?y .
    ?o rdf:type ?type.
    FILTER NOT EXISTS
    {
      { ?o rdf:type v:Dynamic }
      UNION
      { ?o rdf:type v:Static }
    }
  }
}



/// OUTPUT FROM running "qparse --explain --print=op -v":


(prefix ((raw: <http://v/raw#>)
         (rdfs: <http://www.w3.org/2000/01/rdf-schema#>)
         (rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>)
         (owl: <http://www.w3.org/2002/07/owl#>)
         (v: <http://b/dir/>))
  (project (?count)
    (extend ((?count ?.0))
      (group () ((?.0 (count ?x)))
        (conditional
          (sequence
            (join
              (bgp (triple ?x rdf:type v:Person))
              (project (?x)
                (minus
                  (sequence
                    (table (vars ?/id)
                      (row [?/id "b01.xml"])
                      (row [?/id "f5f.xml"])
                    )
                    (bgp
                      (triple ?x v:hasSnapshot ?/snapshot)
                      (triple ?/snapshot rdf:type v:DS)
                      (triple ?/snapshot v:mdId ?/id)
                    ))
                  (sequence
                    (table (vars ?/id)
                      (row [?/id "def.xml"])
                      (row [?/id "191.xml"])
                    )
                    (bgp
                      (triple ?x v:hasSnapshot ?/snapshot)
                      (triple ?/snapshot rdf:type v:DS)
                      (triple ?/snapshot v:mdId ?/id)
                    )))))
            (bgp (triple ?x ?p ?o)))
          (sequence
            (filter (notexists
                       (union
                         (bgp (triple ?o rdf:type v:Dynamic))
                         (bgp (triple ?o rdf:type v:Static))))
              (bgp (triple ?o ?x ?y)))
            (bgp (triple ?o rdf:type ?type))))))))