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获取mysql COLUMNS信息

Posted by 夏泽民 May 16, 2021

如何保证orm 和数据库的一致性，可以通过 show tables; 获取所有的数据库 然后 show databases from xxx； 获取所有的表 然后用 SHOW FULL COLUMNS FROM xxx； 获取表的所有列详细信息

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mysql AUTO_INCREMENT

Posted by 夏泽民 May 16, 2021

主键自增：

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wss RSS/VSS/USS/PSS

Posted by 夏泽民 May 10, 2021

Working Set Size (WSS) is how much memory an application needs to keep working. Your application may have 100 Gbytes of main memory allocated and page mapped, but it is only touching 50 Mbytes each second to do its job. That’s the working set size: the “hot” memory that is frequently used. It is useful to know for capacity planning and scalability analysis.

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mysql实现upsert

Posted by 夏泽民 May 10, 2021

upsert(update or insert), 即更新或写入。 MySQL中实现upsert操作方式： 思路：通过判断插入的记录里是否存在主键索引或唯一索引冲突，来决定是插入还是更新。当出现主键索引或唯一索引冲突时则进行update操作，否则进行insert操作。 实现：使用 ON DUPLICATE KEY UPDATE insert into demo(a,b,c,d,e,f) values(1,1,1,2,2,2) ON DUPLICATE KEY UPDATE a=2,b=2,c=3,d=4,e=5,f=6; 因为已经存在由abc三列组成唯一索引数据：1，1，1，本次又写入demo(a,b,c,d,e,f) values(1,1,1,2,2,2)，会造成唯一索引冲突。 因此，会触发ON DUPLICATE KEY 后面的 UPDATE a=2,b=2,c=3,d=4,e=5,f=6操作。 至此，已经实现upsert功能。请记住 ON DUPLICATE KEY UPDATE的用法。

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redis的部署模式

Posted by 夏泽民 May 10, 2021

1.单机模式

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