MySQL 大数据操作注意事项_MySQL
程序员文章站
2022-06-01 08:09:18
...
MySQL 大数据操作注意事项
http://netkiller.github.io/journal/mysql.parallel.html
Mr. Neo Chen (netkiller), 陈景峰(BG7NYT)
中国广东省深圳市龙华新区民治街道溪山美地
518131
+86 13113668890
+86 755 29812080
版权 © 2011, 2012, 2013, 2014 http://netkiller.github.io
版权声明
转载请与作者联系,转载时请务必标明文章原始出处和作者信息及本声明。
|
|
2014-05-16
摘要 我的系列文档Netkiller Architect 手札 | Netkiller Developer 手札 | Netkiller PHP 手札 | Netkiller Python 手札 | Netkiller Testing 手札 | Netkiller Cryptography 手札 |
Netkiller Linux 手札 | Netkiller Debian 手札 | Netkiller CentOS 手札 | Netkiller FreeBSD 手札 | Netkiller Shell 手札 | Netkiller Security 手札 |
Netkiller Web 手札 | Netkiller Monitoring 手札 | Netkiller Storage 手札 | Netkiller Mail 手札 | Netkiller Docbook 手札 | Netkiller Version 手札 |
Netkiller Database 手札 | Netkiller PostgreSQL 手札 | Netkiller MySQL 手札 | Netkiller NoSQL 手札 | Netkiller LDAP 手札 | Netkiller Network 手札 |
Netkiller Cisco IOS 手札 | Netkiller H3C 手札 | Netkiller Multimedia 手札 | Netkiller Perl 手札 | Netkiller Amateur Radio 手札 |
目录
- 1. 关于 delete
- 2. 关于 update
- 3. 关于创建索引
- 4. 关于 OPTIMIZE
- 5. 确保SELECT不被受阻
1. 关于 delete
delete from mytable 必死无疑,你需要分批删除,尽量缩小每个批次删除的记录数,delete 是可以并行执行的,你可以同时运行多个删除操作
mysql> show processlist;+--------+-----------------+---------------------+-----------+---------+-------+-----------------------------+--------------------------------------------------------+| Id | User | Host | db | Command | Time | State | Info |+--------+-----------------+---------------------+-----------+---------+-------+-----------------------------+--------------------------------------------------------+| 1 | event_scheduler | localhost | NULL | Daemon | 52 | Waiting for next activation | NULL || 115986 | dba | localhost | example | Query | 0 | NULL | show processlist || 117446 | dba | localhost | example | Query | 20 | updating | delete from mytable where OPEN_TIME like '2011.11.28%' || 117525 | dba | localhost | example | Query | 2 | updating | delete from mytable where OPEN_TIME like '2011.12.02%' || 117526 | dba | localhost | example | Query | 49 | updating | delete from mytable where OPEN_TIME like '2011.12.12%' || 117527 | dba | localhost | example | Query | 6 | updating | delete from mytable where OPEN_TIME like '2011.12.21%' || 117528 | dba | localhost | example | Query | 64 | updating | delete from mytable where OPEN_TIME like '2011.12.30%' || 117546 | dba | localhost | example | Query | 33 | updating | delete from mytable where OPEN_TIME like '2011.11.10%' |+--------+-----------------+---------------------+-----------+---------+-------+-----------------------------+--------------------------------------------------------+23 rows in set (0.00 sec)
2. 关于 update
在电商领域常常遇到一个问题“调价”,经常需要调整一批商品的价格, 程序猿一条预警搞定有没有?
update goods set price=price+10 where category_id = xxx
在开发,测试环境是可以通过测试的,一旦部署到生产环境,必死无疑
3. 关于创建索引
大表创建索引需要很久的时间,通常要经历 manage keys 与 copy to tmp table 的过程
mysql> show processlist;+--------+-----------------+---------------------+----------+---------+-------+-----------------------------+------------------------------------------------------------------+| Id | User | Host | db | Command | Time | State | Info |+--------+-----------------+---------------------+----------+---------+-------+-----------------------------+------------------------------------------------------------------+| 1 | event_scheduler | localhost | NULL | Daemon | 47 | Waiting for next activation | NULL || 115986 | dba | localhost | example | Query | 0 | NULL | show processlist || 118814 | dba | 192.168.6.20:50459 | example | Query | 8 | copy to tmp table | ALTER TABLE `mytable` ADD INDEX `modifiy_time` (`MODIFY_TIME`) |+--------+-----------------+---------------------+----------+---------+-------+-----------------------------+------------------------------------------------------------------+17 rows in set (0.00 sec)
删除索引,也需要经理 copy to tmp table 过程,漫长的等待
mysql> show processlist;+--------+-----------------+---------------------+--------------+---------+-------+-----------------------------+-------------------------------------------------+| Id | User | Host | db | Command | Time | State | Info |+--------+-----------------+---------------------+--------------+---------+-------+-----------------------------+-------------------------------------------------+| 1 | event_scheduler | localhost | NULL | Daemon | 11 | Waiting for next activation | NULL || 115986 | dba | localhost | example | Query | 0 | NULL | show processlist || 118814 | dba | 192.168.6.20:50459 | example | Query | 4 | copy to tmp table | ALTER TABLE `mytable` DROP INDEX `modifiy_time` |+--------+-----------------+---------------------+--------------+---------+-------+-----------------------------+-------------------------------------------------+17 rows in set (0.00 sec)
所以数据设计要深思熟虑,做到提前未雨绸缪,不要亡羊补牢
4. 关于 OPTIMIZE
OPTIMIZE 的操作是将当前表复制到临时表操作后再删除当前表,最后将临时表改名
mysql> show processlist;+--------+-----------------+---------------------+---------------------------+---------+-------+-----------------------------+--------------------------+| Id | User | Host | db | Command | Time | State | Info |+--------+-----------------+---------------------+---------------------------+---------+-------+-----------------------------+--------------------------+| 1 | event_scheduler | localhost | NULL | Daemon | 14 | Waiting for next activation | NULL || 115835 | dba | 192.168.6.20:49664 | example | Query | 9 | copy to tmp table | OPTIMIZE TABLE `mytable` || 115986 | dba | localhost | example | Query | 0 | NULL | show processlist |+--------+-----------------+---------------------+---------------------------+---------+-------+-----------------------------+--------------------------+17 rows in set (0.00 sec)
5. 确保SELECT不被受阻
使用各种手段保证select操作不被受阻,只要select一直可以查询网站前端就能提供80%的功能,一旦select受阻一切都是浮云。
保证 select 操作优先于其他操作
UPDATE [LOW_PRIORITY] [IGNORE] tbl_name SET col_name1=expr1 [, col_name2=expr2 ...] [WHERE where_definition] [ORDER BY ...] [LIMIT row_count]
update的时候增加 LOW_PRIORITY 参数,可以降低更新语句的优先级。
my.cnf
[mysqld] low_priority_updates=1
或者启动是添加--low-priority-updates参数
全局开启
SET @@global.low_priority_updates = 1;
适用于本次会话连接
SET @@session.low_priority_updates = 1;