executeBatch）

最新更新
2023.1.26 感谢大家的反馈和支持，对于文中设计到的一些内容进行更正和修补，请看文末附加部分。

总结

Mybatis内置的ExecutorType有3种，默认的是simple单句模式，该模式下它为每个语句的执行创建一个新的预处理语句，单句提交sql；batch模式重复使用已经预处理的语句，并且批量执行所有语句，大批量模式下性能更优。
- 请注意batch模式在Insert操作时事务没有提交之前，是没有办法获取到自增的id，所以请根据业务情况使用。
- 使用simple模式提交10000条数据，时间为19s，batch模式为6s ，大致情况如此，优化的具体还要看提交的语句情况。
如果需要使用 foreach来优化数据插入的话，需要将每次插入的记录控制在 10-100 左右是比较快的，建议每次100来分割数据，也就是分而治之思想。

普通插入

默认的插入方式是遍历insert语句，单条执行，效率肯定低下，如果成堆插入，更是性能有问题。

INSERT INTO `table1` (`field1`, `field2`) VALUES ("data1", "data2");
INSERT INTO `table1` (`field1`, `field2`) VALUES ("data1", "data2");
INSERT INTO `table1` (`field1`, `field2`) VALUES ("data1", "data2");
INSERT INTO `table1` (`field1`, `field2`) VALUES ("data1", "data2");
INSERT INTO `table1` (`field1`, `field2`) VALUES ("data1", "data2");

foreach 优化插入

如果要优化插入速度时，可以将许多小型操作组合到一个大型操作中。理想情况下，这样可以在单个连接中一次性发送许多新行的数据，并将所有索引更新和一致性检查延迟到最后才进行。

<insert id="batchInsert" parameterType="java.util.List">
    insert into table1 (field1, field2) values
    <foreach collection="list" item="t" index="index" separator=","> 
        (#{t.field1}, #{t.field2})
    </foreach>
</insert>

翻译成sql语句也就是

INSERT INTO `table1` (`field1`, `field2`) 
VALUES ("data1", "data2"),
("data1", "data2"),
("data1", "data2"),
("data1", "data2"),
("data1", "data2");

foreach 遇到数量大，性能瓶颈

项目实践发现，当表的列数较多（超过20），以及一次性插入的行数较多（上万条）时，插入性能非常差，通常需要20分钟以上

这个时候就需要观察曲线了，10-100个来讲是很快的，当然也要根据项目请来看，总之建议100个就ok了，不要太高。

executeBatch方法

批量执行的一种方式，使用PreparedStatement预编译进行优化。

int insertNum = 100;
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/xxx?useUnicode=true&characterEncoding=UTF-8&useServerPrepStmts=false&rewriteBatchedStatements=true","root","root123");
connection.setAutoCommit(false);
PreparedStatement ps = connection.prepareStatement(
        "insert into table1(field1) values(?)");
for (int i = 0; i < insertNum; i++) {
    ps.setString(1,"大狼狗"+insertNum);
    ps.addBatch();
}
ps.executeBatch();
connection.commit();
connection.close();

开启ExecutorType.BATCH模式

简单的讲就是openSession的时候带上参数ExecutorType.BATCH，可以几乎无损优化你的代码性能。

SqlSession session = sessionFactory.openSession(ExecutorType.BATCH);
for (Model model : list) {
    session.insert("insertStatement", model);
}
session.flushStatements();

BatchInsert模式

也是官方针对批量数据插入优化的方法之一

SqlSession session = sqlSessionFactory.openSession(ExecutorType.BATCH);
try {
    TableMapper mapper = session.getMapper(TableMapper.class);
    //自定义你的方法来获取需要插入的数据
    List<TableRecord> records = getRecordsToInsert();
 	//BatchInsert
    BatchInsert<TableRecord> batchInsert = insert(records)
            .into(table)
            .map(id).toProperty("id")
            .map(field1).toProperty("field1")
            .map(field2).toProperty("field2")
            .build()
            .render(RenderingStrategy.MYBATIS3);
    batchInsert.insertStatements().stream().forEach(mapper::insert);
    session.commit();
} finally {
    session.close();
}

附加2023.1.26新年更新

感谢大家的反馈，这里有些方法确实过时了，现更新以下内容：

BatchInsert 应该更新为 MultiRowInsertStatementProvider，
带来mybatis-plus批量插入方法，

更多详情欢迎移步官方文档 Mybatis Insert Statements

by zhengkai.blog.csdn.net

附加1.1 `BatchInsert` 应该更新为 `MultiRowInsertStatementProvider` ：

// 单条插入模式
//...
    SimpleTableRecord row = new SimpleTableRecord();
    row.setId(100);
    row.setFirstName("Joe");
    row.setLastName("Jones");
    row.setBirthDate(new Date());
    row.setEmployed(true);
    row.setOccupation("Developer");

    InsertStatementProvider<SimpleTableRecord> insertStatement = insert(row)
            .into(simpleTable)
            .map(id).toProperty("id")
            .map(firstName).toProperty("firstName")
            .map(lastName).toProperty("lastName")
            .map(birthDate).toProperty("birthDate")
            .map(employed).toProperty("employed")
            .map(occupation).toProperty("occupation")
            .build()
            .render(RenderingStrategies.MYBATIS3);

    int rows = mapper.insert(insertStatement);
//...

//批量插入对比
    try (SqlSession session = sqlSessionFactory.openSession()) {
        GeneratedAlwaysAnnotatedMapper mapper = session.getMapper(GeneratedAlwaysAnnotatedMapper.class);
        List<GeneratedAlwaysRecord> records = getRecordsToInsert(); // not shown
            
        MultiRowInsertStatementProvider<GeneratedAlwaysRecord> multiRowInsert = insertMultiple(records)
                .into(generatedAlways)
                .map(id).toProperty("id")
                .map(firstName).toProperty("firstName")
                .map(lastName).toProperty("lastName")
                .build()
                .render(RenderingStrategies.MYBATIS3);
            
        int rows = mapper.insertMultiple(multiRowInsert);
    }

附加1.2 `Mybatis-Plus`为service层提供了`ServiceImpl`的实现类，可以直接 `extends ServiceImpl<mapper,object>`进行调用

@Service
public class ObjectServiceImpl extends ServiceImpl<ObjectMapper, MyObject> implements ObjectService{
}

而后就可以使用以下的实现方法了：

    public boolean saveBatch(Collection<T> entityList, int batchSize) {
        String sqlStatement = this.getSqlStatement(SqlMethod.INSERT_ONE);
        return this.executeBatch(entityList, batchSize, (sqlSession, entity) -> {
            sqlSession.insert(sqlStatement, entity);
        });
    }
    protected <E> boolean executeBatch(Collection<E> list, int batchSize, BiConsumer<SqlSession, E> consumer) {
        return SqlHelper.executeBatch(this.entityClass, this.log, list, batchSize, consumer);
    }

SqlHelper.executeBatch的具体的实现如下

    public static <E> boolean executeBatch(Class<?> entityClass, Log log, Collection<E> list, int batchSize, BiConsumer<SqlSession, E> consumer) {
        Assert.isFalse(batchSize < 1, "batchSize must not be less than one", new Object[0]);
        return !CollectionUtils.isEmpty(list) && executeBatch(entityClass, log, (sqlSession) -> {
            int size = list.size();
            int idxLimit = Math.min(batchSize, size);
            int i = 1;

            for(Iterator var7 = list.iterator(); var7.hasNext(); ++i) {
                E element = var7.next();
                consumer.accept(sqlSession, element);
                if (i == idxLimit) {
                    sqlSession.flushStatements();
                    idxLimit = Math.min(idxLimit + batchSize, size);
                }
            }

        });
    }

    public static boolean executeBatch(Class<?> entityClass, Log log, Consumer<SqlSession> consumer) {
        try {
            SqlSessionFactory sqlSessionFactory = sqlSessionFactory(entityClass);
            SqlSessionHolder sqlSessionHolder = (SqlSessionHolder)TransactionSynchronizationManager.getResource(sqlSessionFactory);
            boolean transaction = TransactionSynchronizationManager.isSynchronizationActive();
            SqlSession sqlSession;
            if (sqlSessionHolder != null) {
                sqlSession = sqlSessionHolder.getSqlSession();
                sqlSession.commit(!transaction);
            }

            sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
            if (!transaction) {
                log.warn("SqlSession [" + sqlSession + "] Transaction not enabled");
            }

            boolean var7;
            try {
                consumer.accept(sqlSession);
                sqlSession.commit(!transaction);
                var7 = true;
            } catch (Throwable var15) {
                sqlSession.rollback();
                Throwable unwrapped = ExceptionUtil.unwrapThrowable(var15);
                if (unwrapped instanceof PersistenceException) {
                    MyBatisExceptionTranslator myBatisExceptionTranslator = new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(), true);
                    Throwable throwable = myBatisExceptionTranslator.translateExceptionIfPossible((PersistenceException)unwrapped);
                    if (throwable != null) {
                        throw throwable;
                    }
                }

                throw ExceptionUtils.mpe(unwrapped);
            } finally {
                sqlSession.close();
            }

            return var7;
        } catch (Throwable var17) {
            throw var17;
        }
    }

posted @ 2024-01-02 16:41 CharyGao 阅读(36) 评论(0) 编辑收藏举报

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