Mysql InnoDB 数据更新导致锁表

 一、数据表结构

CREATE TABLE `jx_attach` (
  `attach_id` int(11) NOT NULL AUTO_INCREMENT,
  `feed_id` int(11) DEFAULT NULL ,
  `attach_name` varchar(255) NOT NULL,
  `cycore_file_id` varchar(255) DEFAULT NULL ,  
  `attach_size` bigint(20) NOT NULL DEFAULT '0',
  `complete` smallint(6) NOT NULL DEFAULT '0' ,
  PRIMARY KEY (`attach_id`),
  KEY `jx_trend_attach_FK` (`feed_id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=394160 DEFAULT CHARSET=utf8;

二、现象

  当多个连接同时对一个表的数据进行更新操作,那么速度将会越来越慢,持续一段时间后将出现数据表被锁,从而影响到其它的查询及更新。  

存储过程循环30次更新操作

/*30次更新操作*/
BEGIN
  DECLARE v1 INT DEFAULT 30;
  WHILE v1 > 0 DO
    update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
    SET v1 = v1 - 1;
  END WHILE;
END

执行结果(速度非常慢)

时间: 29.876s

Procedure executed successfully
受影响的行: 0

 

200个数据更新操作,三个数据库连接同时执行

 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
 update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';
...等等

执行结果(持续一段时间后速度越来越慢,出现等待锁) 


# Time: 151208 22:41:24
# User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 2
# Query_time: 1.848644 Lock_time: 0.780778 Rows_sent: 0 Rows_examined: 393382
SET timestamp=1449643284;
update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';

.........
........

# User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 2 # Query_time: 2.868598 Lock_time: 1.558542 Rows_sent: 0 Rows_examined: 393382 SET timestamp=1449643805; update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f'; [root@localhost log]# tail -f slow_query.log # User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 19 # Query_time: 1.356797 Lock_time: 0.000169 Rows_sent: 1 Rows_examined: 393383 SET timestamp=1449643805; SELECT * FROM jx_attach ja,jx_feed jf where ja.feed_id=jf.feed_id and ja.cycore_file_id='56677146da502cd8907eb5b7'; # User@Host: zmduan[zmduan] @ [192.168.235.1] Id: 2 # Query_time: 2.868598 Lock_time: 1.558542 Rows_sent: 0 Rows_examined: 393382 SET timestamp=1449643805; update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';

 

 三、原因分析

MySQL的innodb存储引擎支持行级锁,innodb的行锁是通过给索引项加锁实现的,这就意味着只有通过索引条件检索数据时,innodb才使用行锁,否则使用表锁。根据当前的数据更新语句(update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';),该条件字段cycore_file_id并没有添加索引,所以导致数据表被锁。

 

四、解决办法

为cycore_file_id添加索引

 

五、最终效果(30次更新操作)

时间: 0.094s

Procedure executed successfully
受影响的行: 0

  

posted @ 2015-12-09 15:41 古月天 阅读(...) 评论(...) 编辑 收藏