在每 100 行 10 000 行上使用 flush（） 方法会降低事务速度

我有一个示例项目，使用一个表和一个表。spring-bootspring-data-jpapostgres db

我正在尝试将循环中的 10 000 条记录放入表中并测量执行时间 - 为每 100 条记录启用或禁用类中的方法。INSERTflush()EntityManager

预期的结果是，启用方法的执行时间比禁用方法的执行时间短得多，但实际上我有相反的结果。flush()

用户服务.java

package sample.data;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {
    @Autowired
    UserRepository userRepository;

    public User save(User user) {
        return userRepository.save(user);
    }
}

用户存储库.java

package sample.data;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<User, Long> { }

应用.java

package sample;

import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
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 sample.data.User;
import sample.data.UserService;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@SpringBootApplication
@EnableJpaRepositories(considerNestedRepositories = true)
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Autowired
    private UserService userService;

    @PersistenceContext
    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 <= 10000; i++) {
                    userService.save(new User("name_" + i));

                    if (i % 100 == 0) {
                        entityManager.flush();
                        entityManager.clear();
                    }
                }
                entityManager.close();
                System.out.println("Time: " + (System.currentTimeMillis() - incoming));
            }
        };
    }
}