给你 2 万条数据，怎么快速导入到 MySQL？写得太好了...

一、前言

前两天做了一个导入的功能，导入开始的时候非常慢，导入2w条数据要1分多钟，后来一点一点的优化，从直接把list怼进Mysql中，到分配把list导入Mysql中，到多线程把list导入Mysql中。

时间是一点一点的变少了。非常的爽，最后变成了10s以内。

下面就展示一下过程。

二、直接把list怼进Mysql

使用mybatis的批量导入操作：

@Transactional(rollbackFor = Exception.class)
public int addFreshStudentsNew2(List list, String schoolNo) {
 if (list == null || list.isEmpty()) {
  return 0;
 }
 List studentEntityList = new LinkedList<>();
 List enrollStudentEntityList = new LinkedList<>();
 List allusersEntityList = new LinkedList<>();

 for (FreshStudentAndStudentModel freshStudentAndStudentModel : list) {

  EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity();
  StudentEntity studentEntity = new StudentEntity();
  BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity);
  BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity);
  String operator = TenancyContext.UserID.get();
  String studentId = BaseUuidUtils.base58Uuid();
  enrollStudentEntity.setId(BaseUuidUtils.base58Uuid());
  enrollStudentEntity.setStudentId(studentId);
  enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  enrollStudentEntity.setOperator(operator);
  studentEntity.setId(studentId);
  studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  studentEntity.setOperator(operator);
  studentEntityList.add(studentEntity);
  enrollStudentEntityList.add(enrollStudentEntity);

  AllusersEntity allusersEntity = new AllusersEntity();
  allusersEntity.setId(enrollStudentEntity.getId());
  allusersEntity.setUserCode(enrollStudentEntity.getNemtCode());
  allusersEntity.setUserName(enrollStudentEntity.getName());
  allusersEntity.setSchoolNo(schoolNo);
  allusersEntity.setTelNum(enrollStudentEntity.getTelNum());
  allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号
  allusersEntityList.add(allusersEntity);
 }
  enResult = enrollStudentDao.insertAll(enrollStudentEntityList);
  stuResult = studentDao.insertAll(studentEntityList);
  allResult = allusersFacade.insertUserList(allusersEntityList);

 if (enResult > 0 && stuResult > 0 && allResult) {
  return 10;
 }
 return -10;
}

Mapper.

 insert into tb_enroll_student
 
   id, 
   remark, 
   nEMT_aspiration, 
   nEMT_code, 
   nEMT_score, 
   student_id, 
   identity_card_id, 
   level, 
   major, 
   name, 
   nation, 
   secondary_college, 
   operator, 
   sex, 
   is_delete, 
   account_address, 
   native_place, 
   original_place, 
   used_name, 
   pictrue, 
   join_party_date, 
   political_status, 
   tel_num, 
   is_registry, 
   graduate_school, 
   create_time, 
   update_time    
 values
 
 (
   #{item.id,jdbcType=VARCHAR},
   #{item.remark,jdbcType=VARCHAR},
   #{item.nemtAspiration,jdbcType=VARCHAR},
   #{item.nemtCode,jdbcType=VARCHAR},
   #{item.nemtScore,jdbcType=VARCHAR},
   #{item.studentId,jdbcType=VARCHAR},
   #{item.identityCardId,jdbcType=VARCHAR},
   #{item.level,jdbcType=VARCHAR},
   #{item.major,jdbcType=VARCHAR},
   #{item.name,jdbcType=VARCHAR},
   #{item.nation,jdbcType=VARCHAR},
   #{item.secondaryCollege,jdbcType=VARCHAR},
   #{item.operator,jdbcType=VARCHAR},
   #{item.sex,jdbcType=VARCHAR},
   0,
   #{item.accountAddress,jdbcType=VARCHAR},
   #{item.nativePlace,jdbcType=VARCHAR},
   #{item.originalPlace,jdbcType=VARCHAR},
   #{item.usedName,jdbcType=VARCHAR},
   #{item.pictrue,jdbcType=VARCHAR},
   #{item.joinPartyDate,jdbcType=VARCHAR},
   #{item.politicalStatus,jdbcType=VARCHAR},
   #{item.telNum,jdbcType=VARCHAR},
   #{item.isRegistry,jdbcType=TINYINT},
   #{item.graduateSchool,jdbcType=VARCHAR},
   now(),
   now()  
 ) 
     
 

代码说明：

底层的mapper是通过逆向工程来生成的，批量插入如下，是拼接成类似：insert into tb_enroll_student（）values （），（）…….（）;

这样的缺点是，数据库一般有一个默认的设置，就是每次sql操作的数据不能超过4M。这样插入，数据多的时候，数据库会报错Packet for query is too large (6071393 > 4194304). You can change this value on the server by setting the max_allowed_packet' variable.，虽然我们可以通过

类似 修改 my.ini 加上 max_allowed_packet =67108864，67108864=64M，默认大小4194304 也就是4M

修改完成之后要重启mysql服务，如果通过命令行修改就不用重启mysql服务。

完成本次操作，但是我们不能保证项目单次最大的大小是多少，这样是有弊端的。所以可以考虑进行分组导入。

三、分组把list导入Mysql中

同样适用mybatis批量插入，区别是对每次的导入进行分组计算，然后分多次进行导入：

@Transactional(rollbackFor = Exception.class)
public int addFreshStudentsNew2(List list, String schoolNo) {
 if (list == null || list.isEmpty()) {
  return 0;
 }
 List studentEntityList = new LinkedList<>();
 List enrollStudentEntityList = new LinkedList<>();
 List allusersEntityList = new LinkedList<>();

 for (FreshStudentAndStudentModel freshStudentAndStudentModel : list) {

  EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity();
  StudentEntity studentEntity = new StudentEntity();
  BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity);
  BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity);
  String operator = TenancyContext.UserID.get();
  String studentId = BaseUuidUtils.base58Uuid();
  enrollStudentEntity.setId(BaseUuidUtils.base58Uuid());
  enrollStudentEntity.setStudentId(studentId);
  enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  enrollStudentEntity.setOperator(operator);
  studentEntity.setId(studentId);
  studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  studentEntity.setOperator(operator);
  studentEntityList.add(studentEntity);
  enrollStudentEntityList.add(enrollStudentEntity);

  AllusersEntity allusersEntity = new AllusersEntity();
  allusersEntity.setId(enrollStudentEntity.getId());
  allusersEntity.setUserCode(enrollStudentEntity.getNemtCode());
  allusersEntity.setUserName(enrollStudentEntity.getName());
  allusersEntity.setSchoolNo(schoolNo);
  allusersEntity.setTelNum(enrollStudentEntity.getTelNum());
  allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号
  allusersEntityList.add(allusersEntity);
 }

 int c = 100;
 int b = enrollStudentEntityList.size() / c;
 int d = enrollStudentEntityList.size() % c;

 int enResult = 0;
 int stuResult = 0;
 boolean allResult = false;

 for (int e = c; e <= c * b; e = e + c) {
  enResult = enrollStudentDao.insertAll(enrollStudentEntityList.subList(e - c, e));
  stuResult = studentDao.insertAll(studentEntityList.subList(e - c, e));
  allResult = allusersFacade.insertUserList(allusersEntityList.subList(e - c, e));
 }
 if (d != 0) {
  enResult = enrollStudentDao.insertAll(enrollStudentEntityList.subList(c * b, enrollStudentEntityList.size()));
  stuResult = studentDao.insertAll(studentEntityList.subList(c * b, studentEntityList.size()));
  allResult = allusersFacade.insertUserList(allusersEntityList.subList(c * b, allusersEntityList.size()));
 }

 if (enResult > 0 && stuResult > 0 && allResult) {
  return 10;
 }
 return -10;
}

代码说明：

这样操作，可以避免上面的错误，但是分多次插入，无形中就增加了操作实践，很容易超时。所以这种方法还是不值得提倡的。

再次改进，使用多线程分批导入。

四、多线程分批导入Mysql

依然使用mybatis的批量导入，不同的是，根据线程数目进行分组，然后再建立多线程池，进行导入。

@Transactional(rollbackFor = Exception.class)
public int addFreshStudentsNew(List list, String schoolNo) {
 if (list == null || list.isEmpty()) {
  return 0;
 }
 List studentEntityList = new LinkedList<>();
 List enrollStudentEntityList = new LinkedList<>();
 List allusersEntityList = new LinkedList<>();

 list.forEach(freshStudentAndStudentModel -> {
  EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity();
  StudentEntity studentEntity = new StudentEntity();
  BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity);
  BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity);
  String operator = TenancyContext.UserID.get();
  String studentId = BaseUuidUtils.base58Uuid();
  enrollStudentEntity.setId(BaseUuidUtils.base58Uuid());
  enrollStudentEntity.setStudentId(studentId);
  enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  enrollStudentEntity.setOperator(operator);
  studentEntity.setId(studentId);
  studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard());
  studentEntity.setOperator(operator);
  studentEntityList.add(studentEntity);
  enrollStudentEntityList.add(enrollStudentEntity);

  AllusersEntity allusersEntity = new AllusersEntity();
  allusersEntity.setId(enrollStudentEntity.getId());
  allusersEntity.setUserCode(enrollStudentEntity.getNemtCode());
  allusersEntity.setUserName(enrollStudentEntity.getName());
  allusersEntity.setSchoolNo(schoolNo);
  allusersEntity.setTelNum(enrollStudentEntity.getTelNum());
  allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号
  allusersEntityList.add(allusersEntity);
 });


 int nThreads = 50;

 int size = enrollStudentEntityList.size();
 ExecutorService executorService = Executors.newFixedThreadPool(nThreads);
 List> futures = new ArrayList>(nThreads);

 for (int i = 0; i < nThreads; i++) {
  final List EnrollStudentEntityImputList = enrollStudentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));
  final List studentEntityImportList = studentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));
  final List allusersEntityImportList = allusersEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));

  Callable task1 = () -> {
  studentSave.saveStudent(EnrollStudentEntityImputList,studentEntityImportList,allusersEntityImportList);
   return 1;
  };
  futures.add(executorService.submit(task1));
 }
 executorService.shutdown();
 if (!futures.isEmpty() && futures != null) {
  return 10;
 }
 return -10;
}

代码说明：

上面是通过应用ExecutorService 建立了固定的线程数，然后根据线程数目进行分组，批量依次导入。一方面可以缓解数据库的压力，另一个面线程数目多了，一定程度会提高程序运行的时间。

缺点就是要看服务器的配置，如果配置好的话就可以开多点线程，配置差的话就开小点。

五、小结

通过使用这个操作真是不断的提高了，项目使用技巧也是不错。

 
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原文出处：www.shaoqun.com/a/1601159.html