[JENA-535] Algebra.toQuadForm() does not transform Expressions in Optional clauses

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 2.11.0
• Fix Version/s: Jena 2.11.1
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Tracy Hartford
• Created: 19/Sep/13 19:31
• Updated: 08/Nov/13 11:06
• Resolved: 20/Sep/13 15:24

Description

Our internal testing has flagged up a failure in 2.11.0 in Algebra.toQuadForm() when applied to expressions within an OPTIONAL clause.

The query in question is as follows:

SELECT  *
    WHERE
      { ?s ?p ?o
          OPTIONAL
            { 
              FILTER NOT EXISTS {?s ?p ?o }
            }
      }

The algebra before calling Algebra.toQuadForm() is as follows:

(leftjoin
  (bgp (triple ?s ?p ?o))
  (table unit)
  (notexists (bgp (triple ?s ?p ?o))))

The expected algebra is as follows:

(leftjoin
  (quadpattern (quad <urn:x-arq:DefaultGraphNode> ?s ?p ?o))
  (table unit)
  (notexists (quadpattern (quad <urn:x-arq:DefaultGraphNode> ?s ?p ?o))))

The resulting algebra is as follows:

(leftjoin
  (quadpattern (quad <urn:x-arq:DefaultGraphNode> ?s ?p ?o))
  (table unit)
  (notexists (bgp (triple ?s ?p ?o))))

It appears that the Transform Walkers visit the left and right Ops of the OpLeftJoin but not the ExprList that contains the E_NotExists.