mysql 分区简述

1.查看Mysql版本是否支持分区

   SHOW VARIABLES LIKE '%partition%';

  

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

| Variable_name     | Value |

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

| have_partitioning | YES   |

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

如果VALUE 为YES 则支持分区，
 

2.测试那种存储引擎支持分区

   INOODB引擎  www.2cto.com  

   mysql> Create table engine1(id int) engine=innodb partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)

   MRG_MYISAM引擎

   mysql> Create table engine2(id int) engine=MRG_MYISAM partition by range(id)(partition po values less than(10));

   ERROR 1572 (HY000): Engine cannot be used in partitioned tables

   blackhole引擎

   mysql> Create table engine3(id int) engine=blackhole partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)

   CSV引擎

   mysql> Create table engine4(id int) engine=csv partition by range(id)(partition po values less than(10));

   ERROR 1572 (HY000): Engine cannot be used in partitioned tables

   Memory引擎  www.2cto.com  

   mysql> Create table engine5(id int) engine=memory partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)

   federated引擎

   mysql> Create table engine6(id int) engine=federated partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)

   archive引擎

   mysql> Create table engine7(id int) engine=archive partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)

   myisam 引擎

   mysql> Create table engine8(id int) engine=myisam partition by range(id)(partition po values less than(10));

   Query OK, 0 rows affected (0.01 sec)
 

3.Mysql分区表，分区引擎测试

   表分区的存储引擎相同

   mysql> Create table pengine1(id int) engine=myisam partition by range(id)(partition po values less than(10) engine=myisam, partition p1 values less than(20) engine=myisam);

   Query OK, 0 rows affected (0.05 sec)

   表分区的存储引擎不同

mysql> Create table pengine2(id int) engine=myisam partition by range(id)(partition po values less than(10) engine=myisam, partition p1 values less than(20) engine=innodb);

   ERROR 1497 (HY000): The mix of handlers in the partitions is not allowed in this version of MySQL  www.2cto.com  

  

同一个分区表中的所有分区必须使用同一个存储引擎，并且存储引擎要和主表的保持一致。

 

4.分区类型

   Range:基于一个连续区间的列值，把多行分配给分区；

   LIST：列值匹配一个离散集合；

   Hash:基于用户定义的表达式的返回值选择分区，表达式对要插入表中的列值进行计算。这个函数可以包含SQL中有效的，产生非负整

            数值的任何表达式。

   KEY：类似于HASH分区，区别在于KEY 分区的表达式可以是一列或多列，且MYSQL提供自身的HASH函数。
 

5.RANGE分区MAXVALUE值 及加分区测试；

创建表 PRANGE，最后分区一个分区值是MAXVALUE

mysql> Create table prange(id int) engine=myisam partition by range(id)(partition po values less than(10), partition p1 values less than(20),partition p2 values less than maxvalue);

Query OK, 0 rows affected (0.06 sec)

加分区

 

mysql> alter table prange add partition (partition p3 values less than (20));

ERROR 1481 (HY000): MAXVALUE can only be used in last partition definition

在分区P0前面加个分区

mysql> alter table prange add partition (partition p3 values less than (1));

ERROR 1481 (HY000): MAXVALUE can only be used in last partition definition

 

说明有MAXVALUE值后，直接加分区是不可行的；
 

创建表PRANGE1，无MAXVALUE值

mysql> Create table prange1(id int) engine=myisam partition by range(id)(partition po values less than(10), partition p1 values less than(20),partition p2 values less than (30));  www.2cto.com  

Query OK, 0 rows affected (0.08 sec)

从最大值后加个分区

mysql> alter table prange1 add partition (partition p3 values less than (40));

Query OK, 0 rows affected (0.02 sec)

Records: 0 Duplicates: 0 Warnings: 0

从分区的最小值前加个分区

mysql> alter table prange1 add partition (partition p43 values less than (1));

ERROR 1493 (HY000): VALUES LESS THAN value must be strictly increasing for each partition

由此可见，RANGE 的分区方式在加分区的时候，只能从最大值后面加，而最大值前面不可以添加；
 

6. 用时间做分区测试

    create table ptime2(id int,createdate datetime) engine=myisam partition by range (to_days(createdate))

    (partition po values less than (20100801),partition p1 values less than (20100901));

    

    Query OK, 0 rows affected (0.01 sec)

   mysql> create table ptime3(id int,createdate datetime) engine=myisam partition by range (createdate)

   (partition po values less than (20100801),partition p1 values less than (20100901));

    ERROR 1491 (HY000): The PARTITION function returns the wrong type

   

    直接使用时间列不可以，RANGE分区函数返回的列需要是整型。

   

    mysql> create table ptime6(id int,createdate datetime) engine=myisam partition by range (year(createdate))

     (partition po values less than (2010),partition p1 values less than (2011));

    Query OK, 0 rows affected (0.01 sec)  www.2cto.com  

   

    使用年函数也可以分区。
 

7.Mysql可用的分区函数

  

DAY()

DAYOFMONTH()

DAYOFWEEK()

DAYOFYEAR()

DATEDIFF()

EXTRACT()

HOUR()

MICROSECOND()

MINUTE()

MOD()

MONTH()

QUARTER()

SECOND()

TIME_TO_SEC()

TO_DAYS()

WEEKDAY()

YEAR()

YEARWEEK() 等

当然，还有FLOOR（），CEILING() 等，前提是使用这两个分区函数的分区健必须是整型。

要小心使用其中的一些函数，避免犯逻辑性的错误，引起全表扫描。

比如：

create table ptime11(id int,createdate datetime) engine=myisam partition by range (day(createdate)) (partition po values less than (15),partition p1 values less than (31));

mysql> insert into ptime11 values (1,'2010-06-17');

mysql> explain partitions select count(1) from ptime11 where createdate>'2010-08-17'\G;

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

           id: 1

select_type: SIMPLE

        table: ptime11

   partitions: po,p1

         type: ALL

possible_keys: NULL

          key: NULL

      key_len: NULL

          ref: NULL

         rows: 5

        Extra: Using where

1 row in set (0.00 sec)
 

8.主键及约束测试

   分区健不包含在主键内

   mysql> create table pprimary(id int,createdate datetime,primary key(id)) engine=myisam partition by range (day(createdate)) (partition po values less than (15),partition p1 values less than (31));  www.2cto.com  

ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function

分区健包含在主键内

mysql> create table pprimary1(id int,createdate datetime,primary key(id,createdate)) engine=myisam partition by range (day(createdate)) (partition po values less than (15),partition p1 values less than (31));

Query OK, 0 rows affected (0.05 sec)

说明分区健必须包含在主键里面。

 

mysql> create table pprimary2(id int,createdate datetime,uid char(10),primary key(id,createdate),unique key(uid)) engine=myisam partition by range(to_days(createdate))(partition p0 values less than (20100801),partition p1 values less than (20100901));

ERROR 1503 (HY000): A UNIQUE INDEX must include all columns in the table's partitioning function

说明在表上建约束索引会有问题，必须把约束索引列包含在分区健内。
 

mysql> create table pprimary3(id int,createdate datetime,uid char(10),primary key(id,createdate),unique key(createdate)) engine=myisam partition by range(to_days(createdate))(partition p0 values less than (20100801),partition p1 values less than (20100901));

Query OK, 0 rows affected (0.00 sec)

虽然在表上可以加约束索引，但是只有包含在分区健内，这种情况在实际应用过程中会遇到问题，这个问题点在以后的MYSQL 版本中也许会改进。
 

9.子分区测试

只有RANGE和LIST分区才能有子分区，每个分区的子分区数量必须相同，

mysql> create table pprimary7(id int,createdate datetime,uid char(10),primary key(id,createdate)) engine=myisam partition by range(to_days(createdate)) subpartition by hash(to_days(createdate))(partition p0 values less than (20100801) ( subpartition so,subpartition s1) ,partition p1 values less than (20100901) (subpartition s0,subpartition s1));  www.2cto.com  

ERROR 1517 (HY000): Duplicate partition name s1

提示了重复的分区名称错误，这和MYSQL5.1帮助文档中的说明有出入，不知道是不是这个问题在某个小版本中修改过。
 

10.MYSQL分区健NULL值测试；

    MYSQL将NULL值视为0.自动插入最小的分区中。
 

11.MYSQL分区管理测试

mysql> alter table pprimary4 truncate partition p1;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'truncate partition p1' at line 1

5.1版本中还不支持这个语法，5.5中已经支持，很好的一个命令；

ALTER TABLE reorganize 可以重新组织分区。