独特的结果和具有多对多关系的分页

Question

I have a M-to-M relation going from Nomination to User mapped on a "Nominee" table. I have the following method to encapsulate results in a paging class called "ResultPage":

protected ResultPage<T> findPageByCriteria(Criteria criteria, int page,
                                               int pageSize) {
        DataVerify.notNull(criteria);
        DataVerify.greaterThan(page, 0, "Invalid page number");
        DataVerify.isTrue(pageSize >= 0, "Invalid page size");
        if (logger.isDebugEnabled()) {
            logger.debug("Arguments: ");
            logger.debug("Page: " + page);
            logger.debug("Page size: " + pageSize);
        }
        int totalItems = 0;
        List<T> results = null;
        if (pageSize != 0) {
            totalItems = ((Number) criteria.setProjection(Projections.rowCount()).
                    uniqueResult()).intValue();
            criteria.setProjection(null);

            criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
            criteria.addOrder(Order.desc("id"));

            results = criteria.setFirstResult((page-1) * pageSize).
                    setMaxResults(pageSize).list();
        } else {
            results = criteria.setFirstResult((page-1) * pageSize).
                    list();
            totalItems = results.size();
        }

        ResultPage<T> resultsPage = new ResultPage<T>(results, page,
                totalItems,
                (pageSize != 0) ? pageSize :
                        totalItems);
        if (logger.isDebugEnabled()){
            logger.debug("Total Results: " + resultsPage.getTotalItems());
        }
        return resultsPage;
    }

Now fetching is done right. However my results count is not being consistent. This of course only happens when a "Nomination" has more than 1 user assigned to it. It then counts the users instead of the root entity and thus I get totals of "1 to 22" per page instead of "1 to 25" like I have specified - as if there are 22 nominations but 25 users total.

Can I get some help for this? Let me know if I have to clarify.

if anything this is the question that comes as closest as my problem: how to retrieve distinct root entity row count in hibernate?

Answer 1

The solution I use for this problem is to have a first query to only load the IDs of the root entities that satisfy the criteria (ie the IDs of your 25 nominations), and then issue a second query which loads the data of these 25 IDs, by doing a query like the following

select n from Nomination n 
[... joins and fetches] 
where n.id in (:ids)