一、數(shù)據(jù)表結(jié)構(gòu)

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、現(xiàn)象

當(dāng)多個(gè)連接同時(shí)對(duì)一個(gè)表的數(shù)據(jù)進(jìn)行更新操作，那么速度將會(huì)越來越慢，持續(xù)一段時(shí)間后將出現(xiàn)數(shù)據(jù)表被鎖，從而影響到其它的查詢及更新。

存儲(chǔ)過程循環(huán)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

執(zhí)行結(jié)果(速度非常慢)

時(shí)間: 29.876s

Procedure executed successfully

受影響的行: 0

200個(gè)數(shù)據(jù)更新操作，三個(gè)數(shù)據(jù)庫連接同時(shí)執(zhí)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

執(zhí)行結(jié)果(持續(xù)一段時(shí)間后速度越來越慢，出現(xiàn)等待鎖)

# 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 *

FROMjx_attach ja,jx_feed jfwhere 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存儲(chǔ)引擎支持行級(jí)鎖，innodb的行鎖是通過給索引項(xiàng)加鎖實(shí)現(xiàn)的，這就意味著只有通過索引條件檢索數(shù)據(jù)時(shí)，innodb才使用行鎖，否則使用表鎖。根據(jù)當(dāng)前的數(shù)據(jù)更新語句(update jx_attach set complete=1,attach_size=63100 where cycore_file_id='56677142da502cd8907eb58f';)，該條件字段cycore_file_id并沒有添加索引，所以導(dǎo)致數(shù)據(jù)表被鎖。

四、解決辦法

為cycore_file_id添加索引

五、最終效果(30次更新操作)

時(shí)間: 0.094s

Procedure executed successfully

受影響的行: 0

總結(jié)

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