virtuoso optimizer bug

gistfile1.txt

PREFIX rdfs:    <http://www.w3.org/2000/01/rdf-schema#> 
PREFIX dcterms:    <http://purl.org/dc/terms/> 
PREFIX dgtwc:    <http://data-gov.tw.rpi.edu/2009/data-gov-twc.rdf#>
PREFIX foaf:       <http://xmlns.com/foaf/0.1/>
PREFIX dbpedia:       <http://dbpedia.org/resource/>
PREFIX conversion:   <http://purl.org/twc/vocab/conversion/>
SELECT *
WHERE {
	GRAPH <http://purl.org/twc/vocab/conversion/MetaDataset> {
		?dataset a conversion:CatalogedDataset ;
			dcterms:title ?title ;
			dgtwc:agency ?agency ;
			dgtwc:keywords ?keywords ;
			dcterms:description ?description .
		FILTER(
			bif:contains(?title, 'health') ||
			bif:contains(?description, 'health') ||
			bif:contains(?keywords, 'health')
		)
		OPTIONAL {?agency rdfs:label ?agency_label. }
	}
}





*** Error 37000: [Virtuoso Driver][Virtuoso Server]SQ156: Internal Optimized compiler error : dt not found based on cname in sqlo.c:1078.
Please report the statement compiled.