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自5.1開始對分區(qū)(Partition)有支持
= 水平分區(qū)(根據(jù)列屬性按行分)=
舉個簡單例子:一個包含十年發(fā)票記錄的表可以被分區(qū)為十個不同的分區(qū),每個分區(qū)包含的是其中一年的記錄。
=== 水平分區(qū)的幾種模式:===
* Range(范圍) – 這種模式允許DBA將數(shù)據(jù)劃分不同范圍。例如DBA可以將一個表通過年份劃分成三個分區(qū),80年代(1980's)的數(shù)據(jù),90年代(1990's)的數(shù)據(jù)以及任何在2000年(包括2000年)后的數(shù)據(jù)。
* Hash(哈希) – 這中模式允許DBA通過對表的一個或多個列的Hash Key進行計算,最后通過這個Hash碼不同數(shù)值對應的數(shù)據(jù)區(qū)域進行分區(qū),。例如DBA可以建立一個對表主鍵進行分區(qū)的表。
* Key(鍵值) – 上面Hash模式的一種延伸,這里的Hash Key是MySQL系統(tǒng)產(chǎn)生的。
* List(預定義列表) – 這種模式允許系統(tǒng)通過DBA定義的列表的值所對應的行數(shù)據(jù)進行分割。例如:DBA建立了一個橫跨三個分區(qū)的表,分別根據(jù)2004年2005年和2006年值所對應的數(shù)據(jù)。
* Composite(復合模式) - 很神秘吧,哈哈,其實是以上模式的組合使用而已,就不解釋了。舉例:在初始化已經(jīng)進行了Range范圍分區(qū)的表上,我們可以對其中一個分區(qū)再進行hash哈希分區(qū)。
= 垂直分區(qū)(按列分)=
舉個簡單例子:一個包含了大text和BLOB列的表,這些text和BLOB列又不經(jīng)常被訪問,這時候就要把這些不經(jīng)常使用的text和BLOB了劃分到另一個分區(qū),在保證它們數(shù)據(jù)相關(guān)性的同時還能提高訪問速度。
[分區(qū)表和未分區(qū)表試驗過程]
*創(chuàng)建分區(qū)表,按日期的年份拆分
[sql] view plain copy
mysql> CREATE TABLE part_tab ( c1 int default NULL, c2 varchar(30) default NULL, c3 date default NULL) engine=myisam
PARTITION BY RANGE (year(c3)) (PARTITION p0 VALUES LESS THAN (1995),
PARTITION p1 VALUES LESS THAN (1996) , PARTITION p2 VALUES LESS THAN (1997) ,
PARTITION p3 VALUES LESS THAN (1998) , PARTITION p4 VALUES LESS THAN (1999) ,
PARTITION p5 VALUES LESS THAN (2000) , PARTITION p6 VALUES LESS THAN (2001) ,
PARTITION p7 VALUES LESS THAN (2002) , PARTITION p8 VALUES LESS THAN (2003) ,
PARTITION p9 VALUES LESS THAN (2004) , PARTITION p10 VALUES LESS THAN (2010),
PARTITION p11 VALUES LESS THAN MAXVALUE );
注意最后一行,考慮到可能的最大值
*創(chuàng)建未分區(qū)表
[sql] view plain copy
mysql> create table no_part_tab (c1 int(11) default NULL,c2 varchar(30) default NULL,c3 date default NULL) engine=myisam;
*通過存儲過程灌入800萬條測試數(shù)據(jù)
mysql> set sql_mode=''; /* 如果創(chuàng)建存儲過程失敗,則先需設置此變量, bug? */
MySQL> delimiter // /* 設定語句終結(jié)符為 //,因存儲過程語句用;結(jié)束 */
[sql] view plain copy
mysql> CREATE PROCEDURE load_part_tab()
begin
declare v int default 0;
while v < 8000000
do
insert into part_tab
values (v,'testing partitions',adddate('1995-01-01',(rand(v)*36520) mod 3652));
set v = v + 1;
end while;
end
//
mysql> delimiter ;
mysql> call load_part_tab();
Query OK, 1 row affected (8 min 17.75 sec)
[sql] view plain copy
mysql> insert into no_part_tab select * from part_tab;
Query OK, 8000000 rows affected (51.59 sec)
Records: 8000000 Duplicates: 0 Warnings: 0
* 測試SQL性能
[sql] view plain copy
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (0.55 sec)
[sql] view plain copy
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (4.69 sec)
結(jié)果表明分區(qū)表比未分區(qū)表的執(zhí)行時間少90%。
* 通過explain語句來分析執(zhí)行情況
[sql] view plain copy
mysql > explain select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31'\G
/* 結(jié)尾的\G使得mysql的輸出改為列模式 */
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: no_part_tab
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 8000000
Extra: Using where
1 row in set (0.00 sec)
[sql] view plain copy
mysql> explain select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: part_tab
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 798458
Extra: Using where
1 row in set (0.00 sec)
explain語句顯示了SQL查詢要處理的記錄數(shù)目
* 試驗創(chuàng)建索引后情況
[sql] view plain copy
mysql> create index idx_of_c3 on no_part_tab (c3);
Query OK, 8000000 rows affected (1 min 18.08 sec)
Records: 8000000 Duplicates: 0 Warnings: 0
[sql] view plain copy
mysql> create index idx_of_c3 on part_tab (c3);
Query OK, 8000000 rows affected (1 min 19.19 sec)
Records: 8000000 Duplicates: 0 Warnings: 0
創(chuàng)建索引后的數(shù)據(jù)庫文件大小列表:
2008-05-24 09:23 8,608 no_part_tab.frm
2008-05-24 09:24 255,999,996 no_part_tab.MYD
2008-05-24 09:24 81,611,776 no_part_tab.MYI
2008-05-24 09:25 0 part_tab#P#p0.MYD
2008-05-24 09:26 1,024 part_tab#P#p0.MYI
2008-05-24 09:26 25,550,656 part_tab#P#p1.MYD
2008-05-24 09:26 8,148,992 part_tab#P#p1.MYI
2008-05-24 09:26 25,620,192 part_tab#P#p10.MYD
2008-05-24 09:26 8,170,496 part_tab#P#p10.MYI
2008-05-24 09:25 0 part_tab#P#p11.MYD
2008-05-24 09:26 1,024 part_tab#P#p11.MYI
2008-05-24 09:26 25,656,512 part_tab#P#p2.MYD
2008-05-24 09:26 8,181,760 part_tab#P#p2.MYI
2008-05-24 09:26 25,586,880 part_tab#P#p3.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p3.MYI
2008-05-24 09:26 25,585,696 part_tab#P#p4.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p4.MYI
2008-05-24 09:26 25,585,216 part_tab#P#p5.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p5.MYI
2008-05-24 09:26 25,655,740 part_tab#P#p6.MYD
2008-05-24 09:26 8,181,760 part_tab#P#p6.MYI
2008-05-24 09:26 25,586,528 part_tab#P#p7.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p7.MYI
2008-05-24 09:26 25,586,752 part_tab#P#p8.MYD
2008-05-24 09:26 8,160,256 part_tab#P#p8.MYI
2008-05-24 09:26 25,585,824 part_tab#P#p9.MYD
2008-05-24 09:26 8,159,232 part_tab#P#p9.MYI
2008-05-24 09:25 8,608 part_tab.frm
2008-05-24 09:25 68 part_tab.par
* 再次測試SQL性能
[sql] view plain copy
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (2.42 sec) /* 為原來4.69 sec 的51%*/
重啟mysql ( net stop mysql, net start mysql)后,查詢時間降為0.89 sec,幾乎與分區(qū)表相同。
[sql] view plain copy
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1995-12-31';
+----------+
| count(*) |
+----------+
| 795181 |
+----------+
1 row in set (0.86 sec)
* 更進一步的試驗
** 增加日期范圍
[sql] view plain copy
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1997-12-31';
+----------+
| count(*) |
+----------+
| 2396524 |
+----------+
1 row in set (5.42 sec)
[sql] view plain copy
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date '1997-12-31';
+----------+
| count(*) |
+----------+
| 2396524 |
+----------+
1 row in set (2.63 sec)
** 增加未索引字段查詢
[sql] view plain copy
mysql> select count(*) from part_tab where c3 > date '1995-01-01' and c3 < date
'1996-12-31' and c2='hello';
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.75 sec)
[sql] view plain copy
mysql> select count(*) from no_part_tab where c3 > date '1995-01-01' and c3 < date '1996-12-31' and c2='hello';
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (11.52 sec)
= 初步結(jié)論 =
* 分區(qū)和未分區(qū)占用文件空間大致相同 (數(shù)據(jù)和索引文件)
* 如果查詢語句中有未建立索引字段,分區(qū)時間遠遠優(yōu)于未分區(qū)時間
* 如果查詢語句中字段建立了索引,分區(qū)和未分區(qū)的差別縮小,分區(qū)略優(yōu)于未分區(qū)。
= 最終結(jié)論 =
* 對于大數(shù)據(jù)量,建議使用分區(qū)功能。
* 去除不必要的字段
* 根據(jù)手冊, 增加myisam_max_sort_file_size 會增加分區(qū)性能
[分區(qū)命令詳解]
= 分區(qū)例子 =
* RANGE 類型
[sql] view plain copy
CREATE TABLE users (
uid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT '',
email VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY RANGE (uid) (
PARTITION p0 VALUES LESS THAN (3000000)
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1 VALUES LESS THAN (6000000)
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx',
PARTITION p2 VALUES LESS THAN (9000000)
DATA DIRECTORY = '/data4/data'
INDEX DIRECTORY = '/data5/idx',
PARTITION p3 VALUES LESS THAN MAXVALUE DATA DIRECTORY = '/data6/data'
INDEX DIRECTORY = '/data7/idx'
);
在這里,將用戶表分成4個分區(qū),以每300萬條記錄為界限,每個分區(qū)都有自己獨立的數(shù)據(jù)、索引文件的存放目錄,與此同時,這些目錄所在的物理磁盤分區(qū)可能也都是完全獨立的,可以提高磁盤IO吞吐量。
* LIST 類型
[sql] view plain copy
CREATE TABLE category (
cid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY LIST (cid) (
PARTITION p0 VALUES IN (0,4,8,12)
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1 VALUES IN (1,5,9,13)
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx',
PARTITION p2 VALUES IN (2,6,10,14)
DATA DIRECTORY = '/data4/data'
INDEX DIRECTORY = '/data5/idx',
PARTITION p3 VALUES IN (3,7,11,15)
DATA DIRECTORY = '/data6/data'
INDEX DIRECTORY = '/data7/idx'
);
分成4個區(qū),數(shù)據(jù)文件和索引文件單獨存放。
* HASH 類型
[sql] view plain copy
CREATE TABLE users (
uid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT '',
email VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY HASH (uid) PARTITIONS 4 (
PARTITION p0
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx',
PARTITION p2
DATA DIRECTORY = '/data4/data'
INDEX DIRECTORY = '/data5/idx',
PARTITION p3
DATA DIRECTORY = '/data6/data'
INDEX DIRECTORY = '/data7/idx'
);
分成4個區(qū),數(shù)據(jù)文件和索引文件單獨存放。
例子:
[sql] view plain copy
CREATE TABLE ti2 (id INT, amount DECIMAL(7,2), tr_date DATE)
ENGINE=myisam
PARTITION BY HASH( MONTH(tr_date) )
PARTITIONS 6;
CREATE PROCEDURE load_ti2()
begin
declare v int default 0;
while v < 80000
do
insert into ti2
values (v,'3.14',adddate('1995-01-01',(rand(v)*3652) mod 365));
set v = v + 1;
end while;
end
//
* KEY 類型
[sql] view plain copy
CREATE TABLE users (
uid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT '',
email VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY KEY (uid) PARTITIONS 4 (
PARTITION p0
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx',
PARTITION p2
DATA DIRECTORY = '/data4/data'
INDEX DIRECTORY = '/data5/idx',
PARTITION p3
DATA DIRECTORY = '/data6/data'
INDEX DIRECTORY = '/data7/idx'
);
分成4個區(qū),數(shù)據(jù)文件和索引文件單獨存放。
* 子分區(qū)
子分區(qū)是針對 RANGE/LIST 類型的分區(qū)表中每個分區(qū)的再次分割。再次分割可以是 HASH/KEY 等類型。例如:
[sql] view plain copy
CREATE TABLE users (
uid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT '',
email VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY RANGE (uid) SUBPARTITION BY HASH (uid % 4) SUBPARTITIONS 2(
PARTITION p0 VALUES LESS THAN (3000000)
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1 VALUES LESS THAN (6000000)
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx'
);
對 RANGE 分區(qū)再次進行子分區(qū)劃分,子分區(qū)采用 HASH 類型。
或者
[sql] view plain copy
CREATE TABLE users (
uid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL DEFAULT '',
email VARCHAR(30) NOT NULL DEFAULT ''
)
PARTITION BY RANGE (uid) SUBPARTITION BY KEY(uid) SUBPARTITIONS 2(
PARTITION p0 VALUES LESS THAN (3000000)
DATA DIRECTORY = '/data0/data'
INDEX DIRECTORY = '/data1/idx',
PARTITION p1 VALUES LESS THAN (6000000)
DATA DIRECTORY = '/data2/data'
INDEX DIRECTORY = '/data3/idx'
);
對 RANGE 分區(qū)再次進行子分區(qū)劃分,子分區(qū)采用 KEY 類型。
= 分區(qū)管理 =
* 刪除分區(qū)
[sql] view plain copy
ALERT TABLE users DROP PARTITION p0;
刪除分區(qū) p0。
* 重建分區(qū)
o RANGE 分區(qū)重建
[sql] view plain copy
ALTER TABLE users REORGANIZE PARTITION p0,p1 INTO (PARTITION p0 VALUES LESS THAN (6000000));
將原來的 p0,p1 分區(qū)合并起來,放到新的 p0 分區(qū)中。
o LIST 分區(qū)重建
[sql] view plain copy
ALTER TABLE users REORGANIZE PARTITION p0,p1 INTO (PARTITION p0 VALUES IN(0,1,4,5,8,9,12,13));
將原來的 p0,p1 分區(qū)合并起來,放到新的 p0 分區(qū)中。
o HASH/KEY 分區(qū)重建
[sql] view plain copy
ALTER TABLE users REORGANIZE PARTITION COALESCE PARTITION 2;
用 REORGANIZE 方式重建分區(qū)的數(shù)量變成2,在這里數(shù)量只能減少不能增加。想要增加可以用 ADD PARTITION 方法。
* 新增分區(qū)
o 新增 RANGE 分區(qū)
[sql] view plain copy
ALTER TABLE category ADD PARTITION (PARTITION p4 VALUES IN (16,17,18,19)
DATA DIRECTORY = '/data8/data'
INDEX DIRECTORY = '/data9/idx');
新增一個RANGE分區(qū)。
o 新增 HASH/KEY 分區(qū)
[sql] view plain copy
ALTER TABLE users ADD PARTITION PARTITIONS 8;
將分區(qū)總數(shù)擴展到8個。
[ 給已有的表加上分區(qū) ]
[sql] view plain copy
alter table results partition by RANGE (month(ttime))
(PARTITION p0 VALUES LESS THAN (1),
PARTITION p1 VALUES LESS THAN (2) , PARTITION p2 VALUES LESS THAN (3) ,
PARTITION p3 VALUES LESS THAN (4) , PARTITION p4 VALUES LESS THAN (5) ,
PARTITION p5 VALUES LESS THAN (6) , PARTITION p6 VALUES LESS THAN (7) ,
PARTITION p7 VALUES LESS THAN (8) , PARTITION p8 VALUES LESS THAN (9) ,
PARTITION p9 VALUES LESS THAN (10) , PARTITION p10 VALUES LESS THAN (11),
PARTITION p11 VALUES LESS THAN (12),
PARTITION P12 VALUES LESS THAN (13) );
默認分區(qū)限制分區(qū)字段必須是主鍵(PRIMARY KEY)的一部分,為了去除此
限制:
[方法1] 使用ID
[sql] view plain copy
mysql> ALTER TABLE np_pk
-> PARTITION BY HASH( TO_DAYS(added) )
-> PARTITIONS 4;
ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function
However, this statement using the id column for the partitioning column is valid, as shown here:
[sql] view plain copy
mysql> ALTER TABLE np_pk
-> PARTITION BY HASH(id)
-> PARTITIONS 4;
Query OK, 0 rows affected (0.11 sec)
Records: 0 Duplicates: 0 Warnings: 0
[方法2] 將原有PK去掉生成新PK
[sql] view plain copy
mysql> alter table results drop PRIMARY KEY;
Query OK, 5374850 rows affected (7 min 4.05 sec)
Records: 5374850 Duplicates: 0 Warnings: 0
[sql] view plain copy
mysql> alter table results add PRIMARY KEY(id, ttime);
Query OK, 5374850 rows affected (6 min 14.86 sec)
Records: 5374850 Duplicates: 0 Warnings: 0
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