Mysql分区技术

在扫描操作中，mysql优化器只扫描保护数据的那个分区以减少扫描范围获得性能的提高。
分区技术使得数据管理变得简单，删除某个分区不会对另外的分区造成影响，分区有系统直接管理不用手工干预。

查询当前的mysql数据库版本是否支持分区
show variables like '%partition%';

分区类型
【RANGE 分区】：
基于属于一个给定连续区间的列值，把多行分配给分区。

【LIST 分区】：
类似于按RANGE分区，区别在于LIST分区是基于列值匹配一个离散值集合中的某个值来进行选择。

【HASH分区】：
基于用户定义的表达式的返回值来进行选择的分区，该表达式使用将要插入到表中的这些行的列值进行计算。这个函数可以包含MySQL中有效的、产生非负整数值的任何表达式。

【KEY分区】

分区：类似于按HASH分区，区别在于KEY分区只支持计算一列或多列，且MySQL服务器提供其自身的哈希函数。必须有一列或多列包含整数值。

【复合分区】：RANGE—HASH,    LIST—HASH,   RANGE—Key,     LIST—Key

[root@node1 ~]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.6.28 Source distribution

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> exit
Bye
[root@node1 ~]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.6.28 Source distribution

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use test;
Database changed
mysql> show tables;
Empty set (0.00 sec)

mysql> show variables like '%partition%';
Empty set (0.00 sec)
【RANGE 分区】： 
 mysql> create table emp_age_range

    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> age int
    -> )
    -> partition by range(age)
    -> (
    -> partition p1 values less than (10),
    -> partition p2 values less than (20),
    -> partition p3 values less than maxvalue
    -> );
Query OK, 0 rows affected (0.80 sec)

mysql> create table emp_birthdate_range
    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by range(year(birthdate))
    -> (
    -> partition p1 values less than (1980),
    -> partition p2 values less than (1990),
    -> partition p3 values less than maxvalue
    -> );
Query OK, 0 rows affected (0.50 sec)
【LIST 分区】 
 mysql> create table emp_deptno_list
  -> (empno  varchar(20) not null ,

    -> empname varchar(20),
    -> deptno  int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by list(deptno)
    -> (
    -> partition p1 values in  (10),
    -> partition p2 values in  (20),
    -> partition p3 values  in  (30)
    -> );
Query OK, 0 rows affected (0.66 sec)

【HASH分区】
 mysql> create table emp_birthday_hash
    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by hash(year(birthdate))
    -> partitions 4;
Query OK, 0 rows affected (0.41 sec)

【KEY分区】
 mysql> create table emp_birthdate_key

    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by key(birthdate)
    -> partitions 4;
Query OK, 0 rows affected (1.00 sec)

【复合分区】
 mysql> create table emp_birthdate_range_hash
    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by range(salary)
    -> subpartition by hash(year(birthdate))
    -> subpartitions 3
    -> (
    -> partition p1 values less than (2000),
    -> partition p2 values less than maxvalue
    -> );
Query OK, 0 rows affected (0.56 sec)

mysql> create table emp_salary_range_key
    -> (empno varchar(20) not null ,
    -> empname varchar(20),
    -> deptno int,
    -> birthdate date not null,
    -> salary int
    -> )
    -> partition by range(salary)
    -> subpartition by key(birthdate)
    -> subpartitions 3
    -> (
    -> partition p1 values less than (2000),
    -> partition p2 values less than maxvalue
    -> );
Query OK, 0 rows affected (0.62 sec)

mysql> CREATE TABLE emp_birthdate_list_hash (
    -> empno varchar(20) NOT NULL,
    -> empname varchar(20) ,
    -> deptno int,
    -> birthdate date NOT NULL,
    -> salary int
    -> 
    -> )
    -> PARTITION BY list (deptno)
    -> subpartition by hash(year(birthdate))
    -> subpartitions 3
    -> (
    -> PARTITION p1 VALUES in  (10),
    -> PARTITION p2 VALUES in  (20)
    -> );
Query OK, 0 rows affected (0.55 sec)

mysql> CREATE TABLE emp_list_key (
    -> empno varchar(20) NOT NULL,
    -> empname varchar(20) ,
    -> deptno int,
    -> birthdate date NOT NULL,
    -> salary int
    -> )
    -> PARTITION BY list (deptno)
    -> subpartition by key(birthdate)
    -> subpartitions 3
    -> (
    -> PARTITION p1 VALUES in  (10),
    -> PARTITION p2 VALUES in  (20)
    -> );
Query OK, 0 rows affected (0.88 sec)

mysql> show tables;
+--------------------------+
| Tables_in_test           |
+--------------------------+
| emp_age_range            |
| emp_birthdate_key        |
| emp_birthdate_list_hash  |
| emp_birthdate_range      |
| emp_birthdate_range_hash |
| emp_birthday_hash        |
| emp_deptno_list          |
| emp_list_key             |
| emp_salary_range_key     |
+--------------------------+
9 rows in set (0.00 sec)

1.可以查看创建分区表的create语句   show create table 表名
2.可以查看表是不是分区表      show table status 
3.查看information_schema.partitions表 ，可以查看表具有哪几个分区、分区的方法、分区中数据的记录数等信息
select 
  *
from information_schema.partitions  where 
  table_schema = schema()  
  and table_name='test';  
4.查看SQL执行计划，explain partitions select语句
通过此语句来显示扫描哪些分区，及他们是如何使用的.
mysql> desc emp_age_range;
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| empno   | varchar(20) | NO   |     | NULL    |       |
| empname | varchar(20) | YES  |     | NULL    |       |
| deptno  | int(11)     | YES  |     | NULL    |       |
| age     | int(11)     | YES  |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
4 rows in set (0.01 sec)

mysql>  show create table emp_age_range;
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table         | Create Table                                                                                                                                                                                                                                                                                                                                                                                                      |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| emp_age_range | CREATE TABLE `emp_age_range` (
  `empno` varchar(20) NOT NULL,
  `empname` varchar(20) DEFAULT NULL,
  `deptno` int(11) DEFAULT NULL,
  `age` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
/*!50100 PARTITION BY RANGE (age)
(PARTITION p1 VALUES LESS THAN (10) ENGINE = InnoDB,
 PARTITION p2 VALUES LESS THAN (20) ENGINE = InnoDB,
 PARTITION p3 VALUES LESS THAN MAXVALUE ENGINE = InnoDB) */ |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.02 sec)

mysql> select 
    ->   partition_name part,  
    ->   partition_expression expr,  
    ->   partition_description descr,  
    ->   table_rows  
    -> from information_schema.partitions  where 
    ->   table_schema = schema()  ;
+------+-----------------+----------+------------+
| part | expr            | descr    | table_rows |
+------+-----------------+----------+------------+
| p1   | age             | 10       |          0 |
| p2   | age             | 20       |          0 |
| p3   | age             | MAXVALUE |          0 |
| p0   | `birthdate`     | NULL     |          0 |
| p1   | `birthdate`     | NULL     |          0 |
| p2   | `birthdate`     | NULL     |          0 |
| p3   | `birthdate`     | NULL     |          0 |
| p1   | deptno          | 10       |          0 |
| p1   | deptno          | 10       |          0 |
| p1   | deptno          | 10       |          0 |
| p2   | deptno          | 20       |          0 |
| p2   | deptno          | 20       |          0 |
| p2   | deptno          | 20       |          0 |
| p1   | year(birthdate) | 1980     |          0 |
| p2   | year(birthdate) | 1990     |          0 |
| p3   | year(birthdate) | MAXVALUE |          0 |
| p1   | salary          | 2000     |          0 |
| p1   | salary          | 2000     |          0 |
| p1   | salary          | 2000     |          0 |
| p2   | salary          | MAXVALUE |          0 |
| p2   | salary          | MAXVALUE |          0 |
| p2   | salary          | MAXVALUE |          0 |
| p0   | year(birthdate) | NULL     |          0 |
| p1   | year(birthdate) | NULL     |          0 |
| p2   | year(birthdate) | NULL     |          0 |
| p3   | year(birthdate) | NULL     |          0 |
| p1   | deptno          | 10       |          0 |
| p2   | deptno          | 20       |          0 |
| p3   | deptno          | 30       |          0 |
| p1   | deptno          | 10       |          0 |
| p1   | deptno          | 10       |          0 |
| p1   | deptno          | 10       |          0 |
| p2   | deptno          | 20       |          0 |
| p2   | deptno          | 20       |          0 |
| p2   | deptno          | 20       |          0 |
| p1   | salary          | 2000     |          0 |
| p1   | salary          | 2000     |          0 |
| p1   | salary          | 2000     |          0 |
| p2   | salary          | MAXVALUE |          0 |
| p2   | salary          | MAXVALUE |          0 |
| p2   | salary          | MAXVALUE |          0 |
+------+-----------------+----------+------------+
41 rows in set (0.01 sec)

mysql> select 
    ->   *
    -> from information_schema.partitions  where 
    ->   table_schema = schema()  ;

原标题：Mysql分区技术

关键词：MYSQL