[Virtuoso-users] SPARQL OPTIONAL/FILTER issues with Virtuoso

[Gregory Williams]

I'm running into what seems like a bug in virtuoso's SPARQL optimizer. I'm 
trying to execute a query using the OPTIONAL/!BOUND trick for negation and 
getting this error message:

Internal error: sparp_gp_detach_all_filters(): optimization tries to break the 
semantics of LEFT OUTER JOIN for OPTIONAL clause

MacTed on #swig told me to send along a copy of the EXPLAIN for the query to 
the list, but EXPLAIN gives me the same error. Strangely, this seems to happen 
only when the optional/filter are within a GRAPH graph pattern. The query I'm 
trying to execute is:


PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX void: <http://rdfs.org/ns/void#>
SELECT DISTINCT ?dataset ?modified
WHERE {
        GRAPH <http://kasei.us/temp/data-gov-times.rdf> {
                ?dataset a void:Dataset;
                        dcterms:modified ?modified .
                OPTIONAL {
                        ?dataset dcterms:modified ?m1 .
                        FILTER(?m1 > ?modified)
                }
                FILTER(!BOUND(?m1))
        }
}
ORDER BY ?dataset

I'm using virtuoso 06.01.3127. Any thoughts on how to get around this problem 
and when this might be fixed (perhaps it is in 6.2?) would be greatly 
appreciated.

thanks,
.greg