[JENA-577] TDB detects attempt to reassign a variable.

• 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, TDB
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 28/Oct/13 20:28
• Updated: 31/Oct/13 15:04
• Resolved: 29/Oct/13 20:42

Description

With TDB, but not with a general in-memory dataset, a query of the form:

PREFIX  :     <http://example/>

SELECT  *
WHERE
  { ?x :p 123
    { SELECT  ?x
      WHERE
        { ?x :p ?o }
    }
  }

(key feature: projection from the subsquery)
causes

20:24:32 ERROR QueryIteratorCloseable    :: QueryFatalException
com.hp.hpl.jena.sparql.ARQInternalErrorException: Attempt to reassign '?x' from '<http://example/x>' to '<http://example/x>'
	at com.hp.hpl.jena.sparql.engine.binding.BindingHashMap.checkAdd(BindingHashMap.java:111)
	at com.hp.hpl.jena.sparql.engine.binding.BindingHashMap.add(BindingHashMap.java:92)
	at com.hp.hpl.jena.sparql.engine.binding.BindingFactory.materialize(BindingFactory.java:60)
	at com.hp.hpl.jena.tdb.solver.QueryEngineTDB$QueryIteratorMaterializeBinding.moveToNextBinding(QueryEngineTDB.java:132)
	at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.nextBinding(QueryIteratorBase.java:154)

Looking at the optimized algebra, TDB is correct.