// doingDynamicDatasetBySpecialDataset => done earlier.
op = A2.unionDefaultGraphQuads(op) ;
// Rewrite so that any explicitly named "default graph" is union graph.
// And set the default graph to be the union graph as well.
DatasetGraphTDB ds = ((DatasetGraphTDB)dsg).duplicate() ;
ds.setEffectiveDefaultGraph(new GraphNamedTDB(ds, Quad.unionGraph)) ;
Explain.explain("REWRITE(Union default graph)", op, context) ;
dsg = ds ;
}
QueryIterator results = super.eval(op, dsg, input, context) ;
results = new QueryIteratorMaterializeBinding(results) ;