/**
* Returns a document test. This test will be called by {@link AxisPath#index} if the context
* value only consists of database nodes.
*
* @param rt root value
* @return document test
*/
static Test get(final Value rt) {
// use simple test if database contains only one document
final Data data = rt.data();
if (data.meta.ndocs == 1) return Test.DOC;
// adopt nodes from existing sequence
if (rt instanceof DBNodeSeq) {
final DBNodeSeq seq = (DBNodeSeq) rt;
return seq.all() ? Test.DOC : new InvDocTest(new IntList(seq.pres()), data);
}
// loop through all documents and add pre values of documents
// not more than 2^31 documents supported
final IntList il = new IntList((int) rt.size());
for (final Item it : rt) il.add(((DBNode) it).pre());
return new InvDocTest(il, data);
}