MYSQL分区表功能测试简析

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 
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 
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

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)); 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)

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: ALLpossible_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)); 
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)); 
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。