/*******************************************************************************
 * Copyright (c) 1998, 2012 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the 
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *      Oracle - initial impl
 ******************************************************************************/
package example;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.NoResultException;
import javax.persistence.Persistence;
import javax.persistence.Query;

import model.*;

/**
 * Simulates a migration of 100,000 objects from MySQL to Oracle.
 * @author James Sutherland
 */
public class TestOptimized extends Test {    

    public static void main(String[] args) throws Exception {
        // Optimization #1 - use agent
        try {
            Test test = new TestOptimized();
            test.setupDatabase();
            test.migrateDatabase();
            test.verifyMigration();
        } catch (Exception error) {
            error.printStackTrace();
        }
    }
            
    public void migrateDatabase() {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("order-opt");
        EntityManagerFactory emfOld = Persistence.createEntityManagerFactory("order-old");
        EntityManager emOld = emfOld.createEntityManager();
        System.out.println("Migrating database.");
        long start = System.currentTimeMillis();
        Query query = emOld.createQuery("Select o from Order o order by o.id");
        // Optimization #2 - batch fetch
        // #2 - a - join fetch
        //Query query = emOld.createQuery("Select o from Order o join fetch o.orderLines");
        // #2 - b - batch fetch (batch fetch is more optimal as avoids duplication of Order data)
        query.setHint("eclipselink.batch", "o.orderLines");
        query.setHint("eclipselink.batch.type", "IN");
        // Optimization #3 - read-only
        query.setHint("eclipselink.read-only", "true");
        // Optimization #4 - pagination
        int pageSize = 500;
        int firstResult = 0;
        query.setFirstResult(firstResult);
        query.setMaxResults(pageSize);
        
        List<Order> orders = query.getResultList();
        boolean done = false;
        while (!done) {
            if (orders.size() < pageSize) {
                done = true;
            }
            EntityManager em = emf.createEntityManager();
            em.getTransaction().begin();
            Query customerQuery = em.createNamedQuery("findCustomByName");
            // Reset old Ids, so they are assigned from the new database.
            for (Order order : orders) {
                order.setId(0);
                customerQuery.setParameter("name", order.getCustomer().getName());
                try {
                    Customer customer = (Customer)customerQuery.getSingleResult();
                    order.setCustomer(customer);
                } catch (NoResultException notPersistedYet) {
                    // Customer does not yet exist, so null out id to have it persisted.
                    order.getCustomer().setId(0);
                }
            }
            for (Order order : orders) {
                em.persist(order);
                // Optimization #5 - avoid n^2 persist calls
                //for (OrderLine orderLine : order.getOrderLines()) {
                //    em.persist(orderLine);
                //}
            }
            em.getTransaction().commit();
            em.close();
            firstResult = firstResult + pageSize;
            query.setFirstResult(firstResult);
            if (!done) {
                orders = query.getResultList();
            }
        }
        emOld.close();
        System.out.println("Migration complete.");
        long end = System.currentTimeMillis();
        System.out.println("Total time:" + (end - start));
        emf.close();     
        emfOld.close();
    }
}