mysql大树据表update很慢解决_MySQL
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mysql大树据表update很慢解决
问题描述：
数据表千万量级，update where gid="adadfadsfasdf"，返回结果显示耗时70ms到1s之间
分析：
表很大，那么update,可能先要取索引，再取页面，但是即使都是磁盘操作，每次磁盘操作耗费5ms，大概花费20，30ms足矣
所以时间肯定是花在io等待上了。
使用 iostat -x -d 1 3 显示等待时间几十毫秒
所以时间确实花在io等待上了
解决方法：
减少io
增大mysql内存，原来是10G，现在搞成50G
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