关于MyCAT字符集的验证

MyCAT默认字符集是UTF8

下面通过查看日志来验证不同的MySQL客户端字符集和服务器字符集对于MyCAT的影响。

日志中与字符集有关的主要有三部分：

1. 初始化MyCAT连接池

2. 心跳检测

3. 在执行SQL语句时的连接同步。

因为MyCAT实现的是三节点的读写分离和自动切换，以下修改的均是localhost节点上MySQL实例的字符集，其它两个点（192.168.244.146和192.168.244.144）均没有修改。默认为

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.01 sec)

一、当客户端字符集（character_set_client）为utf8，服务端字符集（character_set_server）为latin1。

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

MyCAT的日志输出如下：

1. 初始化连接池

2. 心跳检测

3. 在执行SQL语句时的连接同步。

二、当客户端字符集为latin1，服务端字符集也为latin1。

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

MyCAT的日志输出如下：

1. 初始化MyCAT连接池

2. 心跳检测

3. 在执行SQL语句时的连接同步。

三、当客户端字符集为latin1，服务端字符集也为utf8。

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

MyCAT的日志输出如下：

1. 初始化MyCAT连接池

2. 心跳检测

3. 在执行SQL语句时的连接同步。

四、当客户端字符集为utf8，服务端字符集也为utf8。

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

MyCAT的日志输出如下：

1. 初始化MyCAT连接池

2. 心跳检测

3. 在执行SQL语句时的连接同步。

总结：

初始化MyCAT连接池，心跳检测的字符与服务端字符集有关，即character_set_server设定的值。当localhost的MySQL实例的字符集改成utf8后，因为192.168.244.146和192.168.244.144两个节点的MySQL实例的字符集并没有发生变化，所以执行心跳检测时，localhost的字符集为utf8，其它两个节点仍为latin1。

同步连接与客户端字符集有关，即character_set_client设定的值。