Bulk delete in JPA 2.1 using the criteria API

Question

Given the following code that deletes rows in a batch.

List<City> list = ...
int i=0;

for(City city:list)
{
    if(++i%49==0)
    {
        entityManager.flush();
    }

    entityManager.remove(city);
}

The JPA 2.1 criteria API provides CriteriaDelete to perform a bulk delete. Accordingly, the following code executes a DELETE FROM city WHERE id IN(...) query.

CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
CriteriaDelete<City> criteriaDelete = criteriaBuilder.createCriteriaDelete(City.class);

Root<City> root = criteriaDelete.from(City.class);
criteriaDelete.where(root.in(list));
entityManager.createQuery(criteriaDelete).executeUpdate();

But this should not be equivalent of the first case. What is the equivalent of the first case? It should perform deletion in a batch.

Answer 1

The equivalent would be to execute a query to delete a single entity in a for loop, something like:

for(City city:list)
{
    if(++i%49==0)
    {
        entityManager.flush();
    }

    CriteriaBuilder criteriaBuilder=entityManager.getCriteriaBuilder();
    CriteriaDelete<City> criteriaDelete = criteriaBuilder.createCriteriaDelete(City.class);

    Root<City> root = criteriaDelete.from(City.class);
    criteriaDelete.where(root.equal(city));
    entityManager.createQuery(criteriaDelete).executeUpdate();
}

Each of these 50 statements might not get put into the same batch - it depends on if your JPA provider supports batching or not. The loop seems less efficient, as you end up with X statements rather than a single DELETE FROM city WHERE id IN(...) you did with the original bulk delete.