show full columns 和 checking privileges的说明

简介:

线上一个数据库,高并发的。

show processlist 常看到States状态里有很多的 show full columns 和 chekcing privileges;


实验验证下:

use queues;

set profiling = 1;

show full columns from queuing_wx_qr_table ;

show profiles;

show profile for query 1;wKioL1lcgmLRdh6DAACEN3Cj5U8028.png

wKiom1lcgmKR8w__AACEt3wtV-M735.png


原因:

因为show full columns from table_xxx  展示的结果中会列出Privileges列的情况,表里有多少列就会出现多少次checking permissions检查。



show full columns from xxx 这个语句会不会造成性能影响,不确定,没找到相关博客。











本文转自 lirulei90 51CTO博客,原文链接:http://blog.51cto.com/lee90/1944722,如需转载请自行联系原作者
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