Mysql 分区介绍(九) —— 分区管理

发布时间：2020-06-15 14:35:19 来源：网络阅读：3173 作者：AndyMac 栏目：MySQL数据库

一、分区操作

1. 将没有分区的表改为分区表

ALTER TABLE trb3 PARTITION BY KEY(id) PARTITIONS 2;

2. 删除分区

# 删除所有分区, 同时数据丢失
ALTER TABLE es2 REMOVE PARTITIONING;

# 删除指定分区, 数据丢失
ALTER TABLE tr DROP PARTITION p2;

3. SELECT指定分区查询

select * from daily_rank_1_1 partition (p2015_04_24) limit 10;

4. 添加分区

如果设置了MAXVALUE则无法添加新分区, 会提示 MAXVALUE can only be used in last partition definition, 这时可以使用修改分区来解决

ALTER TABLE members ADD PARTITION (PARTITION p3 VALUES LESS THAN (2010));

5. 重新划分分区

ALTER TABLE table1 REORGANIZE PARTITION 要修改的分区名(可以多个, 逗号分隔) INTO (
    PARTITION 新分区1的名字 VALUES LESS THAN (值),
    PARTITION 新分区2的名字 VALUES LESS THAN (值)
    ...
)

修改一个分区成两个分区

alter table daily_rank_1_1 reorganize partition p2015_04_28 into(
partition p2015_04_28 values less than (to_days('2015-04-28')),
partition pmax values less than(MAXVALUE)
);

重新划分多个分区

ALTER TABLE members REORGANIZE PARTITION p0,p1,p2,p3 INTO (
    PARTITION m0 VALUES LESS THAN (1980),
    PARTITION m1 VALUES LESS THAN (2000)
);

分区修改的原则:<br />

1. 不能与原方案有重叠
1. 同时对多个分区划分必须是连续的分区
1. 分区类型不可以更改, 可以通过ALTER TABLE ... PARTITION BY ...实现

6. 修改分区数量(HASH/Key分区)

ALTER TABLE clients COALESCE PARTITION 4;

二、交换分区和子分区

支持交换分区的条件

1. 表自身不是分区表
1. 不是临时表
1. 两个表的结构相同
1. 表不包含外键
1. 表的数据没有出界

如果要执行操作, 必须具有DROP权限<br />

1. 执行 ALTER TABLE ... EXCHANGE PARTITION不会在分区表或交换表上调用任何触发器
1. auto_increment会发生重置

具体操作:
pt是分区表, p是分区或子分区

1. 与非分区表交换分区

CREATE TABLE e (
    id INT NOT NULL,
    fname VARCHAR(30),
    lname VARCHAR(30)
)
    PARTITION BY RANGE (id) (
        PARTITION p0 VALUES LESS THAN (50),
        PARTITION p1 VALUES LESS THAN (100),
        PARTITION p2 VALUES LESS THAN (150),
        PARTITION p3 VALUES LESS THAN (MAXVALUE)
);
INSERT INTO e VALUES
    (1669, "Jim", "Smith"),
    (337, "Mary", "Jones"),
    (16, "Frank", "White"),
    (2005, "Linda", "Black");
mysql> CREATE TABLE e2 LIKE e;
Query OK, 0 rows affected (1.34 sec)
mysql> ALTER TABLE e2 REMOVE PARTITIONING;
Query OK, 0 rows affected (0.90 sec)
Records: 0  Duplicates: 0  Warnings: 0
# 将p0分区的数据写入e2
ALTER TABLE e EXCHANGE PARTITION p0 WITH TABLE e2;

如果没有匹配到数据, 则提示Found row that does not match the partition

2. 交换一个子分区到一个没有分区的表

mysql> CREATE TABLE es (
    ->     id INT NOT NULL,
    ->     fname VARCHAR(30),
    ->     lname VARCHAR(30)
    -> )
    ->     PARTITION BY RANGE (id)
    ->     SUBPARTITION BY KEY (lname)
    ->     SUBPARTITIONS 2 (
    ->         PARTITION p0 VALUES LESS THAN (50),
    ->         PARTITION p1 VALUES LESS THAN (100),
    ->         PARTITION p2 VALUES LESS THAN (150),
    ->         PARTITION p3 VALUES LESS THAN (MAXVALUE)
    ->     );
Query OK, 0 rows affected (2.76 sec)
mysql> INSERT INTO es VALUES
    ->     (1669, "Jim", "Smith"),
    ->     (337, "Mary", "Jones"),
    ->     (16, "Frank", "White"),
    ->     (2005, "Linda", "Black");
Query OK, 4 rows affected (0.04 sec)
Records: 4  Duplicates: 0  Warnings: 0
mysql> CREATE TABLE es2 LIKE es;
Query OK, 0 rows affected (1.27 sec)
mysql> ALTER TABLE es2 REMOVE PARTITIONING;
Query OK, 0 rows affected (0.70 sec)
Records: 0  Duplicates: 0  Warnings: 0
# 将p3sp0的数据交换到es2表
mysql> ALTER TABLE es EXCHANGE PARTITION p3sp0 WITH TABLE es2;
Query OK, 0 rows affected (0.29 sec)

如果一个表拥有子分区, 则不能移动这个父分区到表中

三、分区维护

重建分区
删除所有记录存储在分区，然后重新插入它们。整理碎片
```
ALTER TABLE t1 REBUILD PARTITION p0, p1;
```
优化分区
优化分区来回收未使用的空间和整理的分区中的数据文件
```
ALTER TABLE t1 OPTIMIZE PARTITION p0, p1;
```
分析分区

ALTER TABLE t1 ANALYZE PARTITION p3;

检查分区
```
ALTER TABLE trb3 CHECK PARTITION p1;
```
修复分区
```
ALTER TABLE t1 REPAIR PARTITION p0,p1;
```

获取分区有效信息

mysql> SHOW CREATE TABLE trb3\G
*************************** 1. row ***************************
   Table: trb3
Create Table: CREATE TABLE `trb3` (
`id` int(11) default NULL,
`name` varchar(50) default NULL,
`purchased` date default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
PARTITION BY RANGE (YEAR(purchased)) (
PARTITION p0 VALUES LESS THAN (1990) ENGINE = MyISAM,
PARTITION p1 VALUES LESS THAN (1995) ENGINE = MyISAM,
PARTITION p2 VALUES LESS THAN (2000) ENGINE = MyISAM,
PARTITION p3 VALUES LESS THAN (2005) ENGINE = MyISAM
)
1 row in set (0.00 sec)

select *
from INFORMATION_SCHEMA.PARTITIONS

四、分区修剪

在执行sql时, 优化器会自动根据分区的条件, 进行分区选择来提高性能。

分区修剪的条件: <br />

1. partition_column = constant
1. partition_column IN (constant1, constant2, ..., constantN)
  where条件中包含<，>，< =，> =，和< > 等之间范围查询的时候, 就可以使用分区修剪
  SELECT、UPDATE和DELETE都可以修剪分区, 但是INSERT无法修剪分区

五、分区选择

在执行操作的时候优化器会根据语句自动进行修剪, 但是在有些时候是不同的:

要检查的分区由语句的发布者指定，与分区剪枝不同，它是自动的。
而分区修剪仅适用于查询，分区明确的选择是查询和多个DML语句支持。
支持的语句: SELECT、DELETE、INSERT、REPLACE、UPDATE、LOAD DATA.、LOAD XML.

具体的语句:

      PARTITION (partition_names)

      partition_names:
          partition_name, ...

SELECT * FROM employees PARTITION (p1);

mysql> SELECT * FROM employees PARTITION (p0, p2)
    ->     WHERE lname LIKE 'S%';
+----+-------+-------+----------+---------------+
| id | fname | lname | store_id | department_id |
+----+-------+-------+----------+---------------+
|  4 | Jim   | Smith |        2 |             4 |
| 11 | Jill  | Stone |        1 |             4 |
+----+-------+-------+----------+---------------+
2 rows in set (0.00 sec)

mysql> SELECT id, CONCAT(fname, ' ', lname) AS name
    ->     FROM employees PARTITION (p0) ORDER BY lname;
+----+----------------+
| id | name           |
+----+----------------+
|  3 | Ellen Johnson  |
|  4 | Jim Smith      |
|  1 | Bob Taylor     |
|  2 | Frank Williams |
+----+----------------+
4 rows in set (0.06 sec)

mysql> SELECT store_id, COUNT(department_id) AS c
    ->     FROM employees PARTITION (p1,p2,p3)
    ->     GROUP BY store_id HAVING c > 4;
+---+----------+
| c | store_id |
+---+----------+
| 5 |        2 |
| 5 |        3 |
+---+----------+
2 rows in set (0.00 sec)

你也可以使用PARTITION 在INSERT...SELECT语句上

mysql> CREATE TABLE employees_copy LIKE employees;
Query OK, 0 rows affected (0.28 sec)

mysql> INSERT INTO employees_copy
    ->     SELECT * FROM employees PARTITION (p2);
Query OK, 5 rows affected (0.04 sec)
Records: 5  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM employees_copy;
+----+--------+----------+----------+---------------+
| id | fname  | lname    | store_id | department_id |
+----+--------+----------+----------+---------------+
| 10 | Lou    | Waters   |        2 |             4 |
| 11 | Jill   | Stone    |        1 |             4 |
| 12 | Roger  | White    |        3 |             2 |
| 13 | Howard | Andrews  |        1 |             2 |
| 14 | Fred   | Goldberg |        3 |             3 |
+----+--------+----------+----------+---------------+
5 rows in set (0.00 sec)

也可以在联表中使用

CREATE TABLE stores (
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    city VARCHAR(30) NOT NULL
)
    PARTITION BY HASH(id)
    PARTITIONS 2;

INSERT INTO stores VALUES
    ('', 'Nambucca'), ('', 'Uranga'),
    ('', 'Bellingen'), ('', 'Grafton');

CREATE TABLE departments  (
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(30) NOT NULL
)
    PARTITION BY KEY(id)
    PARTITIONS 2;

INSERT INTO departments VALUES
    ('', 'Sales'), ('', 'Customer Service'),
    ('', 'Delivery'), ('', 'Accounting');

mysql> SELECT
    ->     e.id AS 'Employee ID', CONCAT(e.fname, ' ', e.lname) AS Name,
    ->     s.city AS City, d.name AS department
    -> FROM employees AS e
    ->     JOIN stores PARTITION (p1) AS s ON e.store_id=s.id
    ->     JOIN departments PARTITION (p0) AS d ON e.department_id=d.id
    -> ORDER BY e.lname;
+-------------+---------------+-----------+------------+
| Employee ID | Name          | City      | department |
+-------------+---------------+-----------+------------+
|          14 | Fred Goldberg | Bellingen | Delivery   |
|           5 | Mary Jones    | Nambucca  | Sales      |
|          17 | Mark Morgan   | Bellingen | Delivery   |
|           9 | Andy Smith    | Nambucca  | Delivery   |
|           8 | June Wilson   | Bellingen | Sales      |
+-------------+---------------+-----------+------------+
5 rows in set (0.00 sec)

删除中使用分区选择

mysql> SELECT * FROM employees WHERE fname LIKE 'j%';
+----+-------+--------+----------+---------------+
| id | fname | lname  | store_id | department_id |
+----+-------+--------+----------+---------------+
|  4 | Jim   | Smith  |        2 |             4 |
|  8 | June  | Wilson |        3 |             1 |
| 11 | Jill  | Stone  |        1 |             4 |
+----+-------+--------+----------+---------------+
3 rows in set (0.00 sec)

mysql> DELETE FROM employees PARTITION (p0, p1)
    ->     WHERE fname LIKE 'j%';
Query OK, 2 rows affected (0.09 sec)

mysql> SELECT * FROM employees WHERE fname LIKE 'j%';
+----+-------+-------+----------+---------------+
| id | fname | lname | store_id | department_id |
+----+-------+-------+----------+---------------+
| 11 | Jill  | Stone |        1 |             4 |
+----+-------+-------+----------+---------------+
1 row in set (0.00 sec)

更新中使用分区选择

mysql> UPDATE employees PARTITION (p0)
    ->     SET store_id = 2 WHERE fname = 'Jill';
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0  Changed: 0  Warnings: 0

mysql> SELECT * FROM employees WHERE fname = 'Jill';
+----+-------+-------+----------+---------------+
| id | fname | lname | store_id | department_id |
+----+-------+-------+----------+---------------+
| 11 | Jill  | Stone |        1 |             4 |
+----+-------+-------+----------+---------------+
1 row in set (0.00 sec)

mysql> UPDATE employees PARTITION (p2)
    ->     SET store_id = 2 WHERE fname = 'Jill';
Query OK, 1 row affected (0.09 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM employees WHERE fname = 'Jill';
+----+-------+-------+----------+---------------+
| id | fname | lname | store_id | department_id |
+----+-------+-------+----------+---------------+
| 11 | Jill  | Stone |        2 |             4 |
+----+-------+-------+----------+---------------+
1 row in set (0.00 sec)

INSERT和REPLACE INTO使用分区选择

mysql> INSERT INTO employees PARTITION (p2) VALUES (20, 'Jan', 'Jones', 1, 3);
ERROR 1729 (HY000): Found a row not matching the given partition set
mysql> INSERT INTO employees PARTITION (p3) VALUES (20, 'Jan', 'Jones', 1, 3);
Query OK, 1 row affected (0.07 sec)

mysql> REPLACE INTO employees PARTITION (p0) VALUES (20, 'Jan', 'Jones', 3, 2);
ERROR 1729 (HY000): Found a row not matching the given partition set

mysql> REPLACE INTO employees PARTITION (p3) VALUES (20, 'Jan', 'Jones', 3, 2);
Query OK, 2 rows affected (0.09 sec)

六、分区的限制

1. 无法使用存储过程、存储功能、UDF和插件
1. 无法用户变量或声明变量
1. 不允许位操作

七、性能影响

1. 分区的创建、修改、删除取决于文件系统。应该确保large_files_support启用，open_files_limit设置正确
1. 在执行分区操作时需要上写锁, 但是不影响查询, 分区操作完成后会立即执行插入和更新操作
1. 分区操作，查询、更新往往是MYISAM比INNODB更快
1. 使用索引可以在非分区表提高性能, 使用分区修剪也可以显著的提高性能
1. 加载数据使用缓冲来提高性能。您应该知道缓冲区每分区使用130KB内存来实现这一点。
1. Mysql5.6.7之前, 分区最大数为1024个, 从5.6.7开始, 分区表的数最多是8192个, 包括子分区
1. 分区表不支持查询缓存

Mysql 分区介绍(九) —— 分区管理

向AI问一下细节

Mysql 分区介绍(九) —— 分区管理

一、分区操作

1. 将没有分区的表改为分区表

2. 删除分区

3. SELECT指定分区查询

4. 添加分区

5. 重新划分分区

6. 修改分区数量(HASH/Key分区)

二、交换分区和子分区

1. 与非分区表交换分区

2. 交换一个子分区到一个没有分区的表

三、分区维护

四、分区修剪

五、分区选择

六、分区的限制

七、性能影响

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