[jira] [Commented] (JENA-97) TDB 0.9.0 snapshot sometimes returns a SELECT binding twice

[Simon Helsen (Commented) (JIRA)]

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https://issues.apache.org/jira/browse/JENA-97?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13122359#comment-13122359
 ] 

Simon Helsen commented on JENA-97:
----------------------------------

ok, I tried debugging this. It seems that in the 3 test cases I have which 
repeat one of the bindings, everything seems ok until the projection happens in 
the BindingProject. So I think the returned BindingNodeId is already wrong

So in my attempt to reproduce outside our test framework, I produced a set of 
quads and the associated query which should illustrate the problem. Now, I did 
this using tdbdump and tdbquery respectively, but for some reason, the tdbquery 
is not returning any results even though the index clearly contains the right 
quads.

I have attached the quads to this issue and here you have the query which 
should expose the issue:

PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
PREFIX people: <http://example.org/xmlns/people_aFu6gPBlEeCFPq5DAUl-2A/> 
SELECT ?aUri ?name 
WHERE { 
     ?aUri a people:Person . 
     ?aUri foaf:knows*/foaf:name ?name 
} 

I am executing the tdbquery with the following parameters

--loc=>>mylocation<<
--set tdb:logExec=true 
--set tdb:fileMode=direct
--set tdb:unionDefaultGraph=true
--file tdbquery.txt
--explain

This is the output (which makes no sense to me):

INFO  File mode: direct (forced)
INFO  QUERY
  PREFIX  foaf: <http://xmlns.com/foaf/0.1/>
  PREFIX  people: <http://example.org/xmlns/people_aFu6gPBlEeCFPq5DAUl-2A/>
  
  SELECT  ?aUri ?name
  WHERE
    { ?aUri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> people:Person .
      ?aUri (foaf:knows)*/foaf:name ?name
    }
INFO  ALGEBRA
  (project (?aUri ?name)
    (sequence
      (quadpattern (quad <urn:x-arq:DefaultGraphNode> ?aUri 
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type> 
<http://example.org/xmlns/people_aFu6gPBlEeCFPq5DAUl-2A/Person>))
      (sequence
        (graph <urn:x-arq:DefaultGraphNode>
          (path ?aUri (path* <http://xmlns.com/foaf/0.1/knows>) ??P0))
        (quadpattern (quad <urn:x-arq:DefaultGraphNode> ??P0 
<http://xmlns.com/foaf/0.1/name> ?name)))))
INFO  Execute ::   (ANY ?aUri rdf:type 
<http://example.org/xmlns/people_aFu6gPBlEeCFPq5DAUl-2A/Person>)
---------------
| aUri | name |
===============
---------------

Perhaps someone can try to reproduce this?
                
> TDB 0.9.0 snapshot sometimes returns a SELECT binding twice
> -----------------------------------------------------------
>
>                 Key: JENA-97
>                 URL: https://issues.apache.org/jira/browse/JENA-97
>             Project: Jena
>          Issue Type: Bug
>          Components: TDB
>         Environment: tx-tdb-0.9.0-20110809.130753-7 
>            Reporter: Simon Helsen
>            Assignee: Andy Seaborne
>            Priority: Critical
>
> Very sometimes (rare), it seems that a result set will repeat the first 
> SELECT binding. E.g. 
> SELECT ?a ?b ...
> will bind ?a twice in the result set. It only happens quite rarely, but the 
> same queries behave correctly in TDB 0.8.7 . I suspect they may be caused by 
> the corruptions mentioned in https://issues.apache.org/jira/browse/JENA-91

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