MySQL分区之RANGE分区

环境：

[sql]

mysql> select version()/G;

*************************** 1. row ***************************

version(): 5.5.28

㈠ 主要应用场景

RANGE分区主要用于日期列的分区

例如销售类的表，可以根据年份来分区存储销售记录

如下是对sales表进行分区

[sql]

mysql> create table sales(money int unsigned not null,

-> date datetime

-> )engine=innodb

-> partition by range (year(date)) (

-> partition p2008 values less than (2009),

-> partition p2009 values less than (2010),

-> partition p2010 values less than (2011)

-> );

Query OK, 0 rows affected (0.06 sec)

mysql> insert into sales SELECT 100,'2008-01-01';

Query OK, 1 row affected (0.02 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into sales SELECT 100,'2008-02-01';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into sales SELECT 200,'2008-01-02';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into sales SELECT 100,'2008-03-01';

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into sales SELECT 100,'2009-03-01';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into sales SELECT 200,'2010-03-01';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from sales;

+-------+---------------------+

| money | date |

+-------+---------------------+

| 100 | 2008-01-01 00:00:00 |

| 100 | 2008-02-01 00:00:00 |

| 200 | 2008-01-02 00:00:00 |

| 100 | 2008-03-01 00:00:00 |

| 100 | 2009-03-01 00:00:00 |

| 200 | 2010-03-01 00:00:00 |

+-------+---------------------+

6 rows in set (0.00 sec)

① 便于对sales表管理，如果要删除2008年的数据，我们就不需要执行：

delete from sales where date>= '2008-01-01' and date<'2009-01-01'

而只需删除2008年数据所在的分区即可

[sql]

mysql> alter table sales drop partition p2008;

Query OK, 0 rows affected (0.10 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> select * from sales;

+-------+---------------------+

| money | date |

+-------+---------------------+

| 100 | 2009-03-01 00:00:00 |

| 200 | 2010-03-01 00:00:00 |

+-------+---------------------+

2 rows in set (0.00 sec)

② 另一个好处是加快某些查询操作，例如，我们只需要查询2009年整年的销售额

[sql]

mysql> explain partitions

-> select * from sales

-> where date>='2009-01-01' and date<='2009-12-31'/G;

*************************** 1. row ***************************

id: 1

select_type: SIMPLE

table: sales

partitions: p2009

type: ALL

possible_keys: NULL

key: NULL

key_len: NULL

ref: NULL

rows: 4

Extra: Using where

1 row in set (0.00 sec)

SQL优化器会进行分区修剪，即只搜索p2009

也请注意分区的边界，如date<'2010-01-01',那么优化器会连带搜索p2010分区

㈡ 常见相关问题

① 插入了一个不在分区中定义的值

[sql]

mysql> insert into sales select 200,'2012-12-3';

ERROR 1526 (HY000): Table has no partition for value 2012

mysql> show create table sales /G;

*************************** 1. row ***************************

Table: sales

Create Table: CREATE TABLE `sales` (

`money` int(10) unsigned NOT NULL,

`date` datetime DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=latin1

/*!50100 PARTITION BY RANGE (year(date))

(PARTITION p2009 VALUES LESS THAN (2010) ENGINE = InnoDB,

PARTITION p2010 VALUES LESS THAN (2011) ENGINE = InnoDB) */

1 row in set (0.00 sec)

ERROR:

No query specified

mysql> alter table sales add partition(

-> partition p2012 values less than maxvalue);

Query OK, 0 rows affected (0.04 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> insert into sales select 200,'2012-12-3';

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from sales where date='2012-12-3';

+-------+---------------------+

| money | date |

+-------+---------------------+

| 200 | 2012-12-03 00:00:00 |

+-------+---------------------+

1 row in set (0.00 sec)

② 对RANGE分区的查询，优化器只能对year(),to_days(),to_seconds()和unix_timestamp()这类函数进行优化选择

[sql]

mysql> create table t (date datetime)

-> engine=innodb

-> partition by range (year(date)*100+month(date)) (

-> partition p201201 values less than (201202),

-> partition p201202 values less than (201203),

-> partition p201203 values less than (201204)

-> );

Query OK, 0 rows affected (0.02 sec)

mysql> insert into t select '2012-01-01';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-01-06';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-02-06';

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-01-06';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-03-06';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-02-01';

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from t;

+---------------------+

| date |

+---------------------+

| 2012-01-01 00:00:00 |

| 2012-01-06 00:00:00 |

| 2012-01-06 00:00:00 |

| 2012-02-06 00:00:00 |

| 2012-02-01 00:00:00 |

| 2012-03-06 00:00:00 |

+---------------------+

6 rows in set (0.00 sec)

mysql> explain partitions

-> select * from t

-> where date>='2012-01-01' and date<='2012-01-31'/G;

*************************** 1. row ***************************

id: 1

select_type: SIMPLE

table: t

partitions: p201201,p201202,p201203

type: ALL

possible_keys: NULL

key: NULL

key_len: NULL

ref: NULL

rows: 6

Extra: Using where

1 row in set (0.00 sec)

ERROR:

No query specified

mysql> drop table t;

Query OK, 0 rows affected (0.01 sec)

mysql> create table t (date datetime)

-> engine=innodb

-> partition by range (to_days(date)) (

-> partition p201201 values less than (to_days('2012-02-01')),

-> partition p201201 values less than (to_days('2012-03-01')),

-> partition p201201 values less than (to_days('2012-04-01'))

-> );

mysql> insert into t select '2012-01-02';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-01-03';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-01-08';

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-02-08';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t select '2012-03-08';

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from t;

+---------------------+

| date |

+---------------------+

| 2012-01-02 00:00:00 |

| 2012-01-03 00:00:00 |

| 2012-01-08 00:00:00 |

| 2012-02-08 00:00:00 |

| 2012-03-08 00:00:00 |

+---------------------+

5 rows in set (0.00 sec)

mysql> explain partitions

-> select * from t

-> where date>='2012-01-01' and date<='2012-01-31'/G;

*************************** 1. row ***************************

id: 1

select_type: SIMPLE

table: t

partitions: p1

type: ALL

possible_keys: NULL

key: NULL

key_len: NULL

ref: NULL

rows: 3

Extra: Using where

1 row in set (0.00 sec)