[redland-dev] [Rasqal RDF Query Library 0000417]: SELECT DISTINCT sometimes returns duplicates

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://bugs.librdf.org/mantis/view.php?id=417 
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Reported By:                dbrnz
Assigned To:                
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Project:                    Rasqal RDF Query Library
Issue ID:                   417
Category:                   api
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
Query Language:             SPARQL 
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Date Submitted:             2011-01-28 01:29
Last Modified:              2011-01-28 01:29
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Summary:                    SELECT DISTINCT sometimes returns duplicates
Description: 
This happens when a variable has a NULL value (resulting say from an OPTIONAL
clause), because NULL compared with NULL is returning False.

The reason is buried in rasqal_literal.c -- the following patch fixes it:

diff --git a/src/rasqal_literal.c b/src/rasqal_literal.c
index adc11f8..56f69ba 100644
--- a/src/rasqal_literal.c
+++ b/src/rasqal_literal.c
@@ -2452,7 +2452,7 @@ rasqal_literal_equals_flags(rasqal_literal* l1,
rasqal_literal* l2,
   /* NULL literals */
   if(!l1 || !l2) {
     /* if either is not null, the comparison fails */
-    return (l1 || l2);
+    return !(l1 || l2);
   }
 
 #if RASQAL_DEBUG > 1

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Issue History 
Date Modified    Username       Field                    Change               
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2011-01-28 01:29 dbrnz          New Issue                                    
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