Mysql 调整 Mybatis 批量插入数量限制

先上结论

• Mysql 对语句的长度有限制，默认是 4M。
• Mybatis 对动态语句没有数量上的限制。

Mysql修改长度限制

# 查询当前大小
mysql> select @@max_allowed_packet;
+----------------------+
| @@max_allowed_packet |
+----------------------+
|              4194304 |
+----------------------+
1 row in set (0.00 sec)

# 修改为256M
mysql> SET GLOBAL max_allowed_packet=268435456;
Query OK, 0 rows affected (0.00 sec)

# 退出客户端重新登录
mysql> select @@max_allowed_packet;
+----------------------+
| @@max_allowed_packet |
+----------------------+
|            268435456 |
+----------------------+
1 row in set (0.00 sec)

Mybatis 解析动态SQL的源码。

// 开始解析
public void parse() {
    if (!configuration.isResourceLoaded(resource)) {
        configurationElement(parser.evalNode("/mapper"));
        configuration.addLoadedResource(resource);
        bindMapperForNamespace();
    }

    parsePendingResultMaps();
    parsePendingChacheRefs();
    parsePendingStatements();
}
// 解析mapper
private void configurationElement(XNode context) {
    try {
        String namespace = context.getStringAttribute("namespace");
        if (namespace.equals("")) {
            throw new BuilderException("Mapper's namespace cannot be empty");
        }
        builderAssistant.setCurrentNamespace(namespace);
        cacheRefElement(context.evalNode("cache-ref"));
        cacheElement(context.evalNode("cache"));
        parameterMapElement(context.evalNodes("/mapper/parameterMap"));
        resultMapElements(context.evalNodes("/mapper/resultMap"));
        sqlElement(context.evalNodes("/mapper/sql"));
        buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
    } catch (Exception e) {
        throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e);
    }
}

// 创建 select|insert|update|delete 语句
private void buildStatementFromContext(List list, String requiredDatabaseId) {
    for (XNode context : list) {
        final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
        try {
            statementParser.parseStatementNode();
        } catch (IncompleteElementException e) {
            configuration.addIncompleteStatement(statementParser);
        }
    }
}

// 填充参数，创建语句
public BoundSql getBoundSql(Object parameterObject) {
    DynamicContext context = new DynamicContext(configuration, parameterObject);
    rootSqlNode.apply(context);
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
    SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
    BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
    for (Map.Entry entry : context.getBindings().entrySet()) {
        boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
    }
    return boundSql;
}

从开始到结束， Mybatis 都没有对填充的条数和参数的数量做限制。