问选择180条记录花了2秒

EN

我的桌子很简单：

CREATE TABLE `od_form_items` ( `id` int(11) NOT NULL AUTO_INCREMENT, `formid` int(11) DEFAULT NULL, `items` mediumtext, `template` mediumtext, `draftid` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=420 DEFAULT CHARSET=utf8mb4 ROW_FORMAT=COMPACT

而且它只包含180行：

mysql> select count(*) from od_form_items; +----------+ | count(*) | +----------+ | 180 | +----------+ 1 row in set (0.00 sec)

最长的字符串只是26314字节：

mysql> select length(items) as a from qiban.od_form_items order by a desc limit 1; +-------+ | a | +-------+ | 26314 | +-------+ 1 rows in set (0.01 sec) mysql> select length(template) as a from qiban.od_form_items order by a desc limit 1; +------+ | a | +------+ | 6556 | +------+ 1 rows in set (0.01 sec)

但是在mysql slow_log中，选择所有记录占用了2秒：

mysql> select start_time, query_time, sql_text from mysql.slow_log order by start_time desc limit 10; +---------------------+------------+--------------------------------------------+ | start_time | query_time | sql_text | +---------------------+------------+--------------------------------------------+ | 2017-11-24 10:34:40 | 00:00:02 | SELECT * FROM `od_form_items` +---------------------+------------+--------------------------------------------+ 1 rows in set (0.01 sec)

我应该如何优化它？我应该检查哪些mysql参数？谢谢!