Claus Stadler created JENA-1487:
-----------------------------------

             Summary: Incorrect SPARQL query result set when applying ORDER BY 
after an empty GROUP BY
                 Key: JENA-1487
                 URL: https://issues.apache.org/jira/browse/JENA-1487
             Project: Apache Jena
          Issue Type: Bug
          Components: ARQ
    Affects Versions: Jena 3.6.0
            Reporter: Claus Stadler


Ordering an empty result set must not introduce additional binding, but this 
happens with the following example (run on an arbitrary dataset - including an 
empty one):

{code:sparql}
SELECT ?s
WHERE {
  ?s ?p ?o
  FILTER(false)
}
GROUP BY ?s
ORDER BY DESC(COUNT(?o))
{code}

{code:json}
{
  "head": {
    "vars": [ "s" ]
  } ,
  "results": {
    "bindings": [
      {
# NOTE THIS EMPTY BINDING HERE!        
      }
    ]
  }
}
{code}


The result set is correct without the ORDER BY:

{code:sparql}
SELECT ?s
WHERE {
  ?s ?p ?o
  FILTER(false)
}
GROUP BY ?s
{code}

{code:json}
{
  "head": {
    "vars": [ "s" ]
  } ,
  "results": {
    "bindings": [
# CORRECT      
    ]
  }
}
{code}



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