java - 如何使用hibernate滚动ScrollableResults进行批处理？

Question

假设您已经配置了 hibernate 批处理大小以支持批处理操作。

    blPU.hibernate.jdbc.batch_size=1000

那么如何编写代码块来处理批处理？

Answer 1

    int BATCH_SIZE = 1000;
    DynamicDaoHelper dynamicDaoHelper = new DynamicDaoHelperImpl();
    SessionFactory sessionFactory = dynamicDaoHelper.getSessionFactory((HibernateEntityManager) em);
    Session session = sessionFactory.openSession();
    Transaction tx = session.openTransaction();
    // must use HQL query so that scroll.get(0) returns entity.
    // if use native SQL, scroll.get() returns row object.
    org.hibernate.Query q = session.createQuery(" SELECT p FROM Product p WHERE p.isProcessed = false");
    ScrollableResults scroll = q.setCacheable(false).setFetchSize(100).scroll(ScrollMode.FORWARD_ONLY);
boolean hasNext = scroll.next();
    try {
         List<Product> batchProduct = new ArrayList<Product>(BATCH_SIZE);
         while (hasNext) {
             batchProduct.clear();
             int count = 0;

             // get a batch of products, quantity should be same as BATCH_SIZE
             while (hasNext) {
                Product product = (Product) scroll.get(0);
                batchProduct.add(product);
                count++;
                hasNext = scroll.next();
                if (count % BATCH_SIZE == 0 || !hasNext)
                   break;
             }

             // process batch
             processBatch(batchProduct);

             // persist batch and release memory
             session.flush();
             session.clear();
         }
    } finally {
        scroll.close();
    }
    tx.commit();
    session.close();

注意:调用scroll.next()将导致检查是否存在并移至下一条记录，应使用 boolean 标志仅调用next()一次。