匿名通过本文主要向大家介绍了mysql,优化,分表等相关知识,希望本文的分享对您有所帮助
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) |
+--------------+