有相关测试数据说明从5.1到5.5+，mysql性能会有明显的提升，具体的需要自己建立测试环境去实践下，今天我们就来操作下，并记录下来升级的具体步骤
记录下CentOS 6.4环境将MySQL5.1升级至5.5.36的过程，希望对大家有个参考。
1.为了安全期间，首先需要备份原有数据
2.卸载原有MySQL，先停止原有的MySQL服务，再查找 find / -name mysql
[root@linuxidc /]# find / -name mysql /var/lib/mysql /var/lib/mysql/mysql /usr/lib64/mysql
并移除服务
[root@linuxidc /]# rm -rf /var/lib/mysql [root@linuxidc /]# rm -rf /var/lib/mysql [root@linuxidc /]# rm -rf /usr/lib64/mysql
3.安装cmake
[root@linuxidc download]# wget http://www.cmake.org/files/v2.8/cmake-2.8.12.2.tar.gz [root@linuxidc download]# tarx zvfc cmake-2.8.12.2.tar.gz [root@linuxidc download]# cd cmake-2.8.12.2 [root@linuxidc cmake-2.8.12.2]# ./configure [root@linuxidc cmake-2.8.12.2]# make && make install
4.下载安装MySQL5.5.36
[root@linuxidc download]# wget http://dev.mysql.com/get/Downloads/MySQL-5.5/mysql-5.5.36.tar.gz [root@linuxidc download]# tar xzvf mysql-5.5.36.tar.gz [root@linuxidc download]# cd mysql-5.5.36 [root@linuxidc mysql-5.5.36]# cmake -DCMAKE_INSTALL_PREFIX=/usr/local/mysql -DEXTRA_CHARSETS=all -DDEFAULT_CHARSET=utf8 -DDEFAULT_COLLATION=utf8_general_ci -DWITH_READLINE=1 -DWITH_SSL=system -DWITH_ZLIB=system -DWITH_EMBEDDED_SERVER=1 -DENABLED_LOCAL_INFILE=1 -DMYSQL_DATADIR=/home/mysql [root@linuxidc mysql-5.5.36]# make && make install
在cmake的过程中出错了，提示Could NOT find Curses (missing: CURSES_LIBRARY CURSES_INCLUDE_PATH)
执行以下代码就可以了，执行好之后继续cmake，然后再make && make install
[root@localhost mysql-5.5.36]# rm CMakeCache.txt [root@localhost mysql-5.5.36]# yum install ncurses-devel
5.接下来需要把之前备份下来的my.cnf文件，复制至/etc/my.cnf
MySQL会读取/etc/my.cnf /etc/mysql/my.cnf /usr/local/mysql/etc/my.cnf /.my.cnf。左边的文件优先级是最高的
6.配置好之后，我们就启动mysql，发现有一个问题启动MySQL提示:The server quit without updating PID file(…)失败
查看my.cnf文件设置的日记文件地址/var/log/mysqld.log，错误提示如下
170715 12:31:36 mysqld_safe mysqld from pid file /var/lib/mysql/linuxidc.pid ended 170715 12:57:48 mysqld_safe Starting mysqld daemon with databases from /home/mysql 170715 12:57:48 InnoDB: The InnoDB memory heap is disabled 170715 12:57:48 InnoDB: Mutexes and rw_locks use GCC atomic builtins 170715 12:57:48 InnoDB: Compressed tables use zlib 1.2.3 170715 12:57:48 InnoDB: Initializing buffer pool, size = 128.0M 170715 12:57:48 InnoDB: Completed initialization of buffer pool 170715 12:57:48 InnoDB: highest supported file format is Barracuda. 170715 12:57:48 InnoDB: Waiting for the background threads to start 170715 12:57:49 InnoDB: 5.5.36 started; log sequence number 2645823 170715 12:57:49 [ERROR] /usr/local/mysql/bin/mysqld: unknown variable 'default-character-set=utf8' 170715 12:57:49 [ERROR] Aborting
此报错是由/etc/my.cnf配置文件下的[mysqld]设置字符集引起的，解决方法：将default-character-set=utf8 改为 character_set_server=utf8
7.通过mysql -u root -p命令连接mysql。（我们之前有安装过mysql，数据库文件还在，所以不需要再添加用户设置权限了）
出现了错误信息：ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock'
出错原因是我们mysql.sock文件在/usr/lib/mysql/文件夹下
可以尝试通过下面命令连接，并查看mysql版本
[root@linuxidc var]# mysql -u root -p -S /usr/lib/mysql/mysql.sock mysql> select version(); +-----------+ | version() | +-----------+ | 5.5.36 | +-----------+ 1 row in set (0.00 sec)
