#80 6.1.5 VOS: Broken Distinct when querying for distinct graph
Disclaimer: This issue seems to be related to the thread "[Virtuoso-users] Major bug with Virtuoso SPARQL Results" on the user mailing list.
The following query on a fresh 6.1.5 VOS virtuoso.db file that retrieves distinct graphs (graph names / graph uris) seems to be broken:
virtuoso-t -?
Virtuoso Open Source Edition (multi threaded)
Version 6.1.5.3127-pthreads as of Mar 29 2012
Compiled for Linux (x86_64-unknown-linux-gnu)
Copyright (C) 1998-2012 OpenLink Software
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Select Distinct ?g { Graph ?g { ?s ?p ?o } } }
Expected:
http://www.openlinksw.com/schemas/virtrdf#
http://www.w3.org/2002/07/owl#
http://localhost:8890/DAV
Actual:
Empty result set
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Select ?g { Graph ?g { ?s ?p ?o } } }
Without distinct it seems to work, which makes me believe there is an issue is related to the distinct keyword.
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Workaround: Making the original query a subquery while performing the distinct only in the outer query seems to work:
Select Distinct ?g { { Select ?g { Graph ?g { ?s ?p ?o } } } }
Best regards,
Claus