[JENA-229] "SELECT DISTINCT * " produces duplicates when blank nodes are used the graph pattern

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: ARQ 2.9.0, ARQ 2.9.1
• Fix Version/s: ARQ 2.9.1
• Component/s: ARQ
• Assignee: Unassigned
• Reporter: Stephen Allen
• Created: 02/Apr/12 02:52
• Updated: 02/Apr/12 19:25
• Resolved: 02/Apr/12 19:25

Description

When using a blank node in the graph pattern of a query, using "select distinct *" can result in duplicate rows. There is a similar issue with "select reduced *"

Steps to reproduce:

1) Load the "books" database [1]
2) Add an additional statement [2]
3) Run the following query:
PREFIX books: <http://example.org/book/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
select distinct *
where

{ ?book dc:title ?title . ?book dc:creator [] . }

You see that you get a duplicate result for book5.

If you change the query to:
PREFIX books: <http://example.org/book/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
select distinct ?book ?title
where

{ ?book dc:title ?title . ?book dc:creator [] . }

You do not get duplicates.

[1] http://svn.apache.org/repos/asf/incubator/jena/Jena2/Fuseki/trunk/Data/books.ttl
[2] <http://example.org/book/book5> <http://purl.org/dc/elements/1.1/creator> "Sir Example" .