// (filter (quadpattern ...))
if ( opFilter.getSubOp() instanceof OpQuadPattern )
{
OpQuadPattern quadPattern = (OpQuadPattern)opFilter.getSubOp() ;
DatasetGraphTDB ds = (DatasetGraphTDB)execCxt.getDataset() ;
return optimizeExecuteQuads(ds, input,
quadPattern.getGraphNode(), quadPattern.getBasicPattern(),
opFilter.getExprs(), execCxt) ;
}