mysql互为主从的环境为什么会出现数据不一致
发布时间：2022-01-16 05:31:15 所属栏目：MySql教程 来源：互联网
导读：本篇内容介绍了mysql互为主从的环境为什么会出现数据不一致的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！ m1： begin; update t1 set c2=b1 where
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本篇内容介绍了“mysql互为主从的环境为什么会出现数据不一致”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！ m1： begin; update t1 set c2='b1' where c1=2; commit; m2: begin; update t1 set c2='b2' where c1=2; commit; m1和m2同时提交，复制不会报错，但是m1和m2的数据不一致，为什么？ 因为sql_thread线程根据主键更新数据，不会校验行数据 如何避免这种问题： 只在单节点进行写入，如 keepalived+双主，MGR，PXC如果多节点写入都有这种问题发生。 例1： 表有主键和自增的情况： root@localhost [testdb]>show create table t1G *************************** 1. row *************************** Table: t1 Create Table: CREATE TABLE `t1` ( `c1` int(11) NOT NULL AUTO_INCREMENT, `c2` varchar(10) DEFAULT NULL, PRIMARY KEY (`c1`) ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8 m1: m2: root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | bbb | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | bbb | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ root@localhost [testdb]>begin; root@localhost [testdb]>begin; root@localhost [testdb]>update t1 set c2='b1' where c1=2; root@localhost [testdb]>update t1 set c2='b2' where c1=2; root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | b1 | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | b2 | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ root@localhost [testdb]>commit; root@localhost [testdb]>commit; root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | b2 | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ root@localhost [testdb]>select * from t1; +----+------+ | c1 | c2 | +----+------+ | 1 | aaa | | 2 | b1 | | 3 | ccc | | 4 | ccc | | 6 | ddd | | 8 | eee | +----+------+ 总结：update一条记录同时提交，有主键的情况下，sql_thread是根据主键匹配行记录，不会校验行数据，所以m1更新了m2中表的记录，m2更新了m1中表的记录。 例2：有没有主键同时更新一行数据的情况： root@localhost [testdb]>show create table t2G *************************** 1. row *************************** Table: t2 Create Table: CREATE TABLE `t2` ( `c1` int(11) DEFAULT NULL, `c2` varchar(20) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8 m1 m2 root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | bbb | +------+------+ root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | bbb | +------+------+ root@localhost [testdb]>begin; root@localhost [testdb]>begin; root@localhost [testdb]>update t2 set c2='b1' where c1=2; root@localhost [testdb]>update t2 set c2='b2' where c1=2; root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | b1 | +------+------+ root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | b2 | +------+------+ root@localhost [testdb]>commit; root@localhost [testdb]>commit; root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | b1 | +------+------+ root@localhost [testdb]>select * from t2; +------+------+ | c1 | c2 | +------+------+ | 1 | aaa | | 2 | b2 | +------+------+ root@localhost [testdb]>show slave statusG Last_Errno: 1032 Last_Error: Could not execute Update_rows event on table testdb.t2; Can't find record in 't2', Error_code: 1032; handler error HA_ERR_END_OF_FILE; the event's master log mysql-bin.000013, end_log_pos 759 root@localhost [testdb]>show slave statusG Last_Errno: 1032 Last_Error: Could not execute Update_rows event on table testdb.t2; Can't find record in 't2', Error_code: 1032; handler error HA_ERR_END_OF_FILE; the event's master log mysql-bin.000026, end_log_pos 3064 总结：update一条记录同时提交，有没有主键的情况下，sql_thread是根据全表扫描匹配行记录，所以m1更新在m2中找不到需要更新的行，报1032错误，m2更新在m1中找不到需要更新的行，也报1032错误。 （编辑：应用网_镇江站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
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