How to use ScrollableResults for Hibernate Queries when joining many different entities

Question

I am using Spring Boot endpoints to return results from database queries. It works fine when using getResultList() on the TypedQuery. However I know I will have to managed very large data sets. I am looking into using ScrollableResults via hibernate but I cannot figure out how to actually reference the contents of each row.

StatelessSession session = ((Session) entityManager.getDelegate()).getSessionFactory().openStatelessSession();

    criteriaQuery.multiselect(selections);

    criteriaQuery.where(predicates.toArray(new Predicate[]{}));

    Query<?> query = session.createQuery(criteriaQuery);
    query.setMaxResults(5);
    query.setFetchSize(1000);
    query.setReadOnly(true);
    ScrollableResults results = query.scroll(ScrollMode.FORWARD_ONLY);

    while(results.next()){
        Object row = results.get();
    }
    results.close();
    session.close();

I have tried results.get(0), results.get(0)[0], results.getLong(0), Object[] row vs Object row, etc. With and without toString() on all of the options. Nothing I do gets more out of the row than the java object reference. I've tried casting as well and get a "cannot cast error". Sometimes I get an error, "query specifies a holder class". Not sure what that means because my criteria query is built by joining 1 or more entities where the entities and selected columns are not known before hand. So I am not actually specifying a class. They entities and selects are specified by user input. Any thoughts? Thanks!

UPDATE: I can do System.out.println(scroll.getType(0)); and in this case observe a long. But when I try to save that long (.getLong(0)) I get the error, "query specifies a holder class". Or again the cannot cast error.

Answer 1

Got it figured out. queryDetails is a CriteriaQuery<Tuple>

StatelessSession session = entityManagers.get("DatasourceName").unwrap(Session.class).getSessionFactory().openStatelessSession();
        
    

Stream<Tuple> resultStream = session.createQuery(queryDetails)
                .setReadOnly(true)
                .setMaxResults(100)
                .setFetchSize(1000)
                .setCacheable(false)
                .getResultStream();
        Iterator<Tuple> itr = resultStream.iterator();
while (itr.hasNext()){
                //Get the next row:
                Tuple row = itr.next();

}