MyBatis-Plus 动态表名插件性能优化

MyBatis-Plus 官方提供「动态表名插件」

参考官方文档：https://baomidou.com/pages/2a45ff/#dynamictablenameinnerinterceptor

但压测下来，通过火焰图分析，此插件比较消耗CPU，对性能产生了一定的影响。

@Bean
@Override
public MybatisPlusInterceptor mybatisPlusInterceptor() {
    MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();

    Map<String, TableNameHandler> tableNameHandlers = Maps.newHashMap();
    tableNameHandlers.put("foobars", (sql, tableName) -> tableName + DateFormatUtils.format(new Date(), "yyyyMMdd"));
    DynamicTableNameInnerInterceptor dynamicTableNameInnerInterceptor = new DynamicTableNameInnerInterceptor(tableNameHandlers);
    interceptor.addInnerInterceptor(dynamicTableNameInnerInterceptor);
    
    return interceptor;
}

以上代码（只是样例）为默认动态表名插件的配置，即访问 foobars 表会，会自动替换成 foobars_当前日期 表名。

如果为写此博客的日期，表名则为 foobars_20230721。

通过源码分析不难发现，每个SQL（无论是否包含动态表名的SQL）都需要解析SQL！！！

如果项目中大部分表不是动态表名的，那就非常得不偿失了。

带来的性能影响 远远大于 带来的收益。

优化后的「动态表名插件」

动态表名插件

public class MyDynamicTableNameInnerInterceptor extends DynamicTableNameInnerInterceptor {

    private final Set<String> mapperClassNames = Sets.newHashSet();

    public MyDynamicTableNameInnerInterceptor() {
        setTableNameHandlerMap(Maps.newHashMap());
    }

    public void addDynamicTable(String tableName, Class<? extends Mapper<?>> mapper, TableNameHandler tableNameHandler) {
        mapperClassNames.add(mapper.getName());
        getTableNameHandlerMap().put(tableName, tableNameHandler);
    }

    @Override
    public void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
        for (String mapperClassName : mapperClassNames) {
            // 通过mapperClassName来判断是否生效，非动态表名的Mapper不执行SQL解析
            if (ms.getId().startsWith(mapperClassName)) {
                super.beforeQuery(executor, ms, parameter, rowBounds, resultHandler, boundSql);
                break;
            }
        }
    }

    @Override
    public void beforePrepare(StatementHandler sh, Connection connection, Integer transactionTimeout) {
        PluginUtils.MPStatementHandler mpSh = PluginUtils.mpStatementHandler(sh);
        MappedStatement ms = mpSh.mappedStatement();
        for (String mapperClassName : mapperClassNames) {
            // 通过mapperClassName来判断是否生效，非动态表名的Mapper不执行SQL解析
            if (ms.getId().startsWith(mapperClassName)) {
                SqlCommandType sct = ms.getSqlCommandType();
                if (sct == SqlCommandType.INSERT || sct == SqlCommandType.UPDATE || sct == SqlCommandType.DELETE) {
                    if (InterceptorIgnoreHelper.willIgnoreDynamicTableName(ms.getId())) return;
                    PluginUtils.MPBoundSql mpBs = mpSh.mPBoundSql();
                    mpBs.sql(this.changeTable(mpBs.sql()));
                }
                break;
            }
        }
    }

}

Bean配置

@Bean
@Override
public MybatisPlusInterceptor mybatisPlusInterceptor() {
    MybatisPlusInterceptor interceptor = super.mybatisPlusInterceptor();

    MyDynamicTableNameInnerInterceptor dynamicTableNameInnerInterceptor = new MyDynamicTableNameInnerInterceptor();
    dynamicTableNameInnerInterceptor.addDynamicTable(
            "foobars",
            FoobarMapper.class,
            (sql, tableName) -> tableName + DateFormatUtils.format(new Date(), "yyyyMMdd")
    );
    interceptor.addInnerInterceptor(dynamicTableNameInnerInterceptor);

    return interceptor;
}

可减少大量的SQL解析！！！