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MySQL中CTRL+C信号处理
- WBOY원래의
- 2016-06-07 15:15:191261검색
欢迎进入Linux社区论坛，与200万技术人员互动交流 >>进入 目的 为了理解MySQL在执行大SQL时，对执行CTRL+C产生的疑惑，本文通过实验测试和源码分析两个方面，对MySQL处理CTRL+C的详细过程进行分析和讲解，从而解除DBA及开发人员对CTRL+C的误解。 测试 首先，
欢迎进入Linux社区论坛，与200万技术人员互动交流 >>进入
目的
为了理解MySQL在执行大SQL时，对执行CTRL+C产生的疑惑，本文通过实验测试和源码分析两个方面，对MySQL处理CTRL+C的详细过程进行分析和讲解，从而解除DBA及开发人员对CTRL+C的误解。
测试
首先，基于线上数据库版本，分别使用MySQL客户端版本5.5.20和5.0.77进行实验测试，一方面排除不同数据库客户端版本造成的差异，另一方面，深入了解不同版本执行CTRL+C产生的差异。
MySQL客户端5.5.20
使用MySQL客户端5.5.20在Session1中执行select sleep(100)语句，在Session2中执行show processlist语句；然后在Session1中执行CTRL+C，在Session中执行show processlist语句，查看当前连接的线程。执行的图如下所示：
Session1：
mysql> select sleep(100);
Ctrl-C -- sending "KILL QUERY 153779" to server ...
Ctrl-C -- query aborted.
ERROR 2013 (HY000): Lost connection to MySQL server during query
Session2:
mysql> show processlist;
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
| 153779 | heng.wang | 127.0.0.1:39882 | NULL | Query | 8 | User sleep | select sleep(100) | 0 | 0 | 1 |
| 153780 | heng.wang | 127.0.0.1:39883 | NULL | Query | 0 | NULL | show processlist | 0 | 0 | 1 |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
2 rows in set (0.00 sec)
mysql> show processlist;
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
| 153780 | heng.wang | 127.0.0.1:39883 | NULL | Query | 0 | NULL | show processlist | 0 | 0 | 1 |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
1 rows in set (0.00 sec)
从以上结果来看，Session1中执行select操作时，Session2中可以查看该连接正在执行，在Session1中执行CTRL+C时，客户端向服务器端发送KILL QUERY
MySQL客户端5.0.77
使用客户端5.0.77执行同样的操作，执行CTRL+C后，观察执行的差异性。具体如下表中所示：
Session1：
mysql> select sleep(100);
Query aborted by Ctrl+C
+------------+
| sleep(100) |
+------------+
| 1 |
+------------+
Session2：
mysql> show processlist;
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
| 153783 | heng.wang | 127.0.0.1:45807 | NULL | Query | 3 | User sleep | select sleep(100) | 0 | 0 | 1 |
| 153784 | heng.wang | 127.0.0.1:45809 | NULL | Query | 0 | NULL | show processlist | 0 | 0 | 1 |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+-------------------+-----------+---------------+-----------+
2 rows in set (0.00 sec)
mysql> show processlist;
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
| 153783 | heng.wang | 127.0.0.1:45807 | NULL | Sleep | 10 | | NULL | 1 | 0 | 1 |
| 153784 | heng.wang | 127.0.0.1:45809 | NULL | Query | 0 | NULL | show processlist | 0 | 0 | 1 |
+--------+-------------+-----------------+------+-------------+---------+-----------------------------------------------------------------------------+------------------+-----------+---------------+-----------+
2 rows in set (0.00 sec)
从以上结果可知，Session1上执行select时，Session2中建立查询连接；在Session1中执行CTRL+C时，显示Query被终止，并且返回执行的错误结果。在Session2中可知，连接的线程仍然存在，但是Query被终止，只是保持连接。
源码分析
为了更进一步对以上测试进行确认，查看MySQL源码进行进一步的求证，同样基于MySQL的5.5.20和5.0.77两个版本进行验证。具体如下：
MySQL 5.5.20源码
MySQL客户端主函数main中，信号函数在源码文件client/mysql.cc:1163，源码如下所示：
signal(SIGINT, handle_sigint); // Catch SIGINT to clean up
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