一、 硬件环境
Master: Dell R720 Intel(R)Xeon(R) CPU E5-2640 v2 @ 2.00GHz
MEM 64G,disk 4*2.5 SAS 网络4* 千兆
Slave: Dell R720 Intel(R)Xeon(R) CPU E5-2640 v2 @ 2.00GHz
MEM 64G,disk 4*2.5 SAS 网络4* 千兆
二、 软件环境
系统软件:
Master: cento5.8
Slave: cento5.8
数据库软件:mysql-5.5.10
三、 问题现象
3.1收到报警,发现问题
2014年XX月XX日收到mysql主从同步监控报警,登陆Slave,用show slavestatus \G; 查看结果如下,错误代码为1146,错误描述为 “库名.表名不存在,插入语句”
图1
3.2 分析解决问题
有上述slave截图中的错误描述,表不存在。我们需要进一步验证,在slave上执行show databases; 查看发现库存在,如图2,继续输入命令,
use 库名;
show tables;
发现表也存在,既然都存在,那为什么会报错“表不存在呢”,边思考,边检查,google了一番,有类似情况,但是解决办法不通用。
冷静,回头仔细看错误提示,有新的发现,错误提示中的表名是大写的,实际库中的表名是小写的。好吧,动手验证一下,
select * from 库名.表名; 表名同样大写,执行完毕,报错信息图2和 图1 的报错信息相同“表不存在”。
select * from 库名.表名; 表名小写,执行完毕,输出正确结果,如图2。

图2
找到原因就好解决问题了。
解决:
stop slave;
show slavestatus \G;
从新克隆一个secureCRT连接,编辑my.cnf配置文件,
在[mysqld]节点下,加入一行:lower_case_table_names=1
保存退出。
/etc/init.d/mysqldrestart
回到数据库操作命令行,执行 start slave;show slave status\G;开启同步,发现报错信息消失,同步恢复。
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
登陆master端,发现master 的my.cnf配置中有lower_case_table_names=1
最后总结原因:slave端my.cnf配置缺少lower_case_table_names=1导致。

To optimize MySQL slow query, slowquerylog and performance_schema need to be used: 1. Enable slowquerylog and set thresholds to record slow query; 2. Use performance_schema to analyze query execution details, find out performance bottlenecks and optimize.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.

MySQL asynchronous master-slave replication enables data synchronization through binlog, improving read performance and high availability. 1) The master server record changes to binlog; 2) The slave server reads binlog through I/O threads; 3) The server SQL thread applies binlog to synchronize data.

MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.

The installation and basic operations of MySQL include: 1. Download and install MySQL, set the root user password; 2. Use SQL commands to create databases and tables, such as CREATEDATABASE and CREATETABLE; 3. Execute CRUD operations, use INSERT, SELECT, UPDATE, DELETE commands; 4. Create indexes and stored procedures to optimize performance and implement complex logic. With these steps, you can build and manage MySQL databases from scratch.

InnoDBBufferPool improves the performance of MySQL databases by loading data and index pages into memory. 1) The data page is loaded into the BufferPool to reduce disk I/O. 2) Dirty pages are marked and refreshed to disk regularly. 3) LRU algorithm management data page elimination. 4) The read-out mechanism loads the possible data pages in advance.

MySQL is suitable for beginners because it is simple to install, powerful and easy to manage data. 1. Simple installation and configuration, suitable for a variety of operating systems. 2. Support basic operations such as creating databases and tables, inserting, querying, updating and deleting data. 3. Provide advanced functions such as JOIN operations and subqueries. 4. Performance can be improved through indexing, query optimization and table partitioning. 5. Support backup, recovery and security measures to ensure data security and consistency.

Full table scanning may be faster in MySQL than using indexes. Specific cases include: 1) the data volume is small; 2) when the query returns a large amount of data; 3) when the index column is not highly selective; 4) when the complex query. By analyzing query plans, optimizing indexes, avoiding over-index and regularly maintaining tables, you can make the best choices in practical applications.


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