TOC
异常排查
MySQL宕机排查
- 查看mysql的运行时常：show global status like ‘uptime’;
MySQL连接超时
- show global variables like ‘%timeout’;
MySQL请求连接进程被主动Kill
- show global status like ‘com_kill’;
SQL statement was too large
show global variables like ‘max_allowed_packet’;
修改参数
- set global max_allowed_packet=1024*1024*16;
零碎记录
AUTO_INCREMENT
AUTO_INCREMENT=1
UNION / UNION ALL
SELECT column_name(s) FROM table_name1 UNION ALL SELECT column_name(s) FROM table_name2
OR VS UNION ALL
https://bertwagner.com/posts/or-vs-union-all-is-one-better-for-performance/
主键自增步长
线上库默认都是步长为2用于防止主从切换出现主键冲突
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