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解决mysql占用cpu资源100%的问题
一个Win2003服务器，以前就跑了一个tomcat实例也没用nginx做前端代理，这个tomcat里面带了不少网站，但是访问量并不是很大，基本属于业务集中型。
解决的过程其实也挺easy，这里记录一下思路。
首先把mysql服务器升级到最新的版本，尽量避免是mysql本身问题。
然后在my.ini里面mysqld里面配置：
slow-query-log = 1
slow-query-log-file = slow.log
重启mysql这样所有'slow'的都会记录到日志里面。
然后再到慢的时候就能看到具体什么sql引发了慢的问题（slow.log在datadir下），最后发现慢的那个表查询里面username没有加索引而且并发不小，开始数据不多还没问题，后来数据多了些达到了十几万的时候，并发查没索引的表就出来问题了，每次比较十几万次字符串是挺要命。
给这个字段加上索引，马上cpu就降下来了。
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