final DocValues y = sources.get(1).getValues(context, reader);
return new DocValues() {
@Override
public void byteVal(int doc, byte[] vals) {
vals[0] = x.byteVal(doc);
vals[1] = y.byteVal(doc);
}
@Override
public void shortVal(int doc, short[] vals) {
vals[0] = x.shortVal(doc);