Query Issues (SPARQL, SQL, etc.) SPARQL Queries Fail After Virtuoso Server Upgrade Use the explain function to diagnose problems that arise with queries after a Virtuoso Server upgrade.Virtuoso Functions Guide - explain http://docs.openlinksw.com/virtuoso/fn_explain.html If you require assistance from OpenLink Product Support, be sure to provide explain output along with the original query. For best results, run the explain function against the problem query using the prior version of Virtuoso and submit the output. This will provide Product Support with something from which a comparison can be drawn.