[英]How the flush method in spring-data-jpa works?
我有使用spring-boot-2.0.3
和spring-data-jpa-2.0.3
和postgresql-9.5.13
示例项目。 它只有三个类: @Repository
@Entity
、 @Repository
和主类。 DB 只有一张表,有两个字段: id
和name
。
我试图INSERT
100 000
记录在循环到表和测量执行时间-启用或禁用flush()
从方法EntityManager
类对于每100个记录。
预期结果是启用flush()
方法的执行时间比禁用方法少得多,但实际上我得到了相反的结果。
问题:我做错了什么?
项目结构:
应用程序属性
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://localhost:5432/twofold
spring.datasource.username=postgres
spring.datasource.password=postgres
用户.java
package twofold.data;
import javax.persistence.*;
@Entity
@Table(name = "users", schema = "public")
public class User {
private Long id;
private String name;
public User() {}
public User(String name) {
this.name = name;
}
@Id
@SequenceGenerator(name = "users_id_seq", sequenceName = "users_id_seq", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.TABLE, generator = "users_id_seq")
@Column(name = "id", nullable = false)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(name = "name", nullable = false, length = 50)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "id: " + id + "; name: " + name + ";";
}
}
用户存储库.java
package twofold.data;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
}
应用程序.java
package twofold;
import twofold.data.User;
import twofold.data.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.transaction.annotation.Transactional;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Autowired
private UserRepository userRepository;
@PersistenceContext
private EntityManager entityManager;
@Bean
public CommandLineRunner addUsers() {
return new CommandLineRunner() {
@Transactional
public void run(String... args) throws Exception {
long incoming = System.currentTimeMillis();
for (int i = 1; i <= 100000; i++) {
userRepository.save(new User(i + "_name"));
if (i % 100 == 0) {
entityManager.flush();
entityManager.clear();
}
}
System.out.println("Time: " + (System.currentTimeMillis()-incoming));
}
};
}
}
您必须设置以下休眠属性。
<property name="hibernate.jdbc.batch_size" value="25" />
<property name="hibernate.order_inserts" value="true" />
<property name="hibernate.order_updates" value="true" />
然后这样做:
int entityCount = 50;
int batchSize = 25;
EntityManager entityManager = entityManagerFactory().createEntityManager();
EntityTransaction entityTransaction = entityManager.getTransaction();
try {
entityTransaction.begin();
for (int i = 0; i < entityCount; i++) {
if (i > 0 && i % batchSize == 0) {
entityTransaction.commit();
entityTransaction.begin();
entityManager.clear();
}
Post post = new Post(
String.format("Post %d", i + 1)
);
entityManager.persist(post);
}
entityTransaction.commit();
} catch (RuntimeException e) {
if (entityTransaction.isActive()) {
entityTransaction.rollback();
}
throw e;
} finally {
entityManager.close();
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.