Mysql 查询日志slow
今天看 Mysql 性能优化的时候看到了对于 Long_query_time 的设置，突然想起昨天在论坛看到的一个帖子遇到类的问题，将 slow_launch_time 的时间设置为 2, 也开启了慢查询日志，但是没有看到日志生成。 自己在网上查了一下，其实 slow_launch_time 的设定跟慢
今天看Mysql性能优化的时候看到了对于Long_query_time值的设置，突然想起昨天在论坛看到的一个帖子遇到类似的问题，将slow_launch_time的时间设置为2,也开启了慢查询日志，但是没有看到日志生成。
自己在网上查了一下，其实slow_launch_time的设定跟慢查询日志的查询阀值设定不同，表示了thread create的一个阀值，如果thread create的时间超过了这个值，这变量slow_launch_time的值加1.
而设置Long_query_time表示超过多少秒的查询就写入日志，默认的是10s,设置为0的话表示记录所有的查询。在Mysql 5.5可以追踪到微秒的查询。
查询long_query_time 的值可以用下面的命令：
show variables like "%long%"
网上看到的几篇文章： http://www.qttc.net/201208182.html
http://asyty.iteye.com/blog/1202943
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