java - How to rewrite subquery in ORDER BY clause in JPA CriteriaQuery

Question

I'm trying to write an SQL query using CriteriaQuery, but I'm having a hard time doing so. This query basically gets a list of shipments and sorts them by their authorization date. This authorization date is represented as the date attribute of the first record in the status transition messages table with an initial status of 3 and a final status of 4. This is my query:

SELECT s.id
FROM shipment s
ORDER BY (SELECT min(stm.date)
          FROM status_transition_message stm
          WHERE stm.initial_status = 1 AND stm.final_status = 3 AND stm.shipment_id = s.id) desc;

I've tried multiple different solutions, but none have worked so far.

My current iteration is as follows:

private void sortByAuthDate(Root<ShipmentTbl> root, CriteriaQuery<?> query, CriteriaBuilder builder, ListSort sort) {
        Subquery<Timestamp> authDateQuery = query.subquery(Timestamp.class);
        Root<StatusTransitionMessageTbl> stmRoot = authDateQuery.from(StatusTransitionMessageTbl.class);

        Predicate shipmentId = builder.equal(stmRoot.<ShipmentTbl>get("shipment").<String>get("id"), root.<String>get("id"));
        Predicate initialStatus = builder.equal(stmRoot.<Integer>get("initialStatus"), 3);
        Predicate finalStatus = builder.equal(stmRoot.<Integer>get("finalStatus"), 4);

        // returns the authorization date for each queried shipment
        authDateQuery.select(builder.least(stmRoot.<Timestamp>get("date")))
                .where(builder.and(shipmentId, initialStatus, finalStatus));

        Expression<Timestamp> authDate = authDateQuery.getSelection();
        Order o = sort.getSortDirection() == ListSort.SortDirection.ASC ? builder.asc(authDate) : builder.desc(authDate);

        query.multiselect(authDate).orderBy(o);
    }

The problem with this solution is that the SQL query generated by the CriteriaQuery does not support subqueries in the ORDER BY clause, causing a parsing exception.

标签： javajpacriteria-api

Answer 1

My CriteriaQuery-fu is not good enough to help you with that part, but you could rewrite your SQL query to this:

SELECT s.id
FROM shipment s
LEFT JOIN status_transition_message stm 
ON stm.initial_status = 1 AND stm.final_status = 3 AND stm.shipment_id = s.id
GROUP BY s.id
ORDER BY min(stm.date) DESC;

To me, this quite likely seems to be a faster solution anyway than running a correlated subquery in the ORDER BY clause, especially on RDBMS with less sophisticated optimisers.