欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

MySQL 分表优化试验代码

程序员文章站 2022-04-25 13:32:44
...

我们的项目中有好多不等于的情况。今天写这篇文章简单的分析一下怎么个优化法。

这里的分表逻辑是根据t_group表的user_name组的个数来分的。
因为这种情况单独user_name字段上的索引就属于烂索引。起不了啥名明显的效果。


DELIMITER $$
DROP PROCEDURE `t_girl`.`sp_split_table`$$
CREATE PROCEDURE `t_girl`.`sp_split_table`()
BEGIN
declare done int default 0;
declare v_user_name varchar(20) default '';
declare v_table_name varchar(64) default '';

declare cur1 cursor for select user_name from t_group group by user_name;

declare continue handler for 1329 set done = 1;

open cur1;
while done 1
do
fetch cur1 into v_user_name;
if not done then

set v_table_name = concat('t_group_',v_user_name);

set @stmt = concat('create table ',v_table_name,' like t_group');
prepare s1 from @stmt;
execute s1;
drop prepare s1;

set @stmt = concat('insert into ',v_table_name,' select * from t_group where user_name = ''',v_user_name,'''');
prepare s1 from @stmt;
execute s1;
drop prepare s1;
end if;
end while;

close cur1;

set @stmt = NULL;
END$$

DELIMITER ;
2、试验表。


mysql> select count(*) from t_group;
+----------+
| count(*) |
+----------+
| 10388608 |
+----------+
1 row in set (0.00 sec)

表结构。
mysql> desc t_group;
+-------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+-------------------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| money | decimal(10,2) | NO | | | |
| user_name | varchar(20) | NO | MUL | | |
| create_time | timestamp | NO | | CURRENT_TIMESTAMP | |
+-------------+------------------+------+-----+-------------------+----------------+
4 rows in set (0.00 sec)

索引情况。

mysql> show index from t_group;
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| t_group | 0 | PRIMARY | 1 | id | A | 10388608 | NULL | NULL | | BTREE | |
| t_group | 1 | idx_user_name | 1 | user_name | A | 8 | NULL | NULL | | BTREE | |
| t_group | 1 | idx_combination1 | 1 | user_name | A | 8 | NULL | NULL | | BTREE | |
| t_group | 1 | idx_combination1 | 2 | money | A | 3776 | NULL | NULL | | BTREE | |
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
4 rows in set (0.00 sec)

PS:
idx_combination1 这个索引是必须的,因为要对user_name来GROUP BY。此时属于松散索引扫描!当然完了后你可以干掉她。
idx_user_name 这个索引是为了加快单独执行constant这种类型的查询。
我们要根据用户名来分表。


mysql> select user_name from t_group where 1 group by user_name;
+-----------+
| user_name |
+-----------+
| david |
| leo |
| livia |
| lucy |
| sarah |
| simon |
| sony |
| sunny |
+-----------+
8 rows in set (0.00 sec)


mysql> show tables like 't_group_%';
+------------------------------+
| Tables_in_t_girl (t_group_%) |
+------------------------------+
| t_group_david |
| t_group_leo |
| t_group_livia |
| t_group_lucy |
| t_group_sarah |
| t_group_simon |
| t_group_sony |
| t_group_sunny |
+------------------------------+
8 rows in set (0.00 sec)




mysql> select count(*) from t_group where user_name = 'david';
+----------+
| count(*) |
+----------+
| 1298576 |
+----------+
1 row in set (1.71 sec)



mysql> select count(*) from t_group_david;
+----------+
| count(*) |
+----------+
| 1298576 |
+----------+
1 row in set (0.00 sec)


mysql> select count(*) from t_group where user_name 'david';
+----------+
| count(*) |
+----------+
| 9090032 |
+----------+
1 row in set (9.26 sec)

mysql> select (select count(*) from t_group) - (select count(*) from t_group_david) as total;
+---------+
| total |
+---------+
| 9090032 |
+---------+
1 row in set (0.00 sec)






mysql> select min(money),max(money) from t_group where user_name = 'david';
+------------+------------+
| min(money) | max(money) |
+------------+------------+
| -6.41 | 500.59 |
+------------+------------+
1 row in set (0.00 sec)

mysql> select sum(money),avg(money) from t_group where user_name = 'david';
+--------------+------------+
| sum(money) | avg(money) |
+--------------+------------+
| 319992383.84 | 246.417910 |
+--------------+------------+
1 row in set (2.15 sec)



mysql> select min(money),max(money) from t_group_david;
+------------+------------+
| min(money) | max(money) |
+------------+------------+
| -6.41 | 500.59 |
+------------+------------+
1 row in set (1.50 sec)

mysql> select sum(money),avg(money) from t_group_david;
+--------------+------------+
| sum(money) | avg(money) |
+--------------+------------+
| 319992383.84 | 246.417910 |
+--------------+------------+
1 row in set (1.68 sec)




mysql> desc t_group_david;
+-------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+-------------------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| money | decimal(10,2) | NO | | | |
| user_name | varchar(20) | NO | MUL | | |
| create_time | timestamp | NO | | CURRENT_TIMESTAMP | |
+-------------+------------------+------+-----+-------------------+----------------+
4 rows in set (0.00 sec)


mysql> alter table t_group_david drop user_name;
Query OK, 1298576 rows affected (7.58 sec)
Records: 1298576 Duplicates: 0 Warnings: 0



mysql> select min(money),max(money) from t_group_david;
+------------+------------+
| min(money) | max(money) |
+------------+------------+
| -6.41 | 500.59 |
+------------+------------+
1 row in set (0.00 sec)


mysql> select sum(money),avg(money) from t_group_david;
+--------------+------------+
| sum(money) | avg(money) |
+--------------+------------+
| 319992383.84 | 246.417910 |
+--------------+------------+
1 row in set (0.94 sec)



mysql> Aborted