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[转]千万级别mysql合并表快速去重

时间:2013年12月31日 | 分类:SQL基本用法 | 评论:0 条 | 浏览:3,358 次

目标:

现有表a和b,把两个表中的数据合并去重到c表中。其中a和b表中数据量大概在2千万左右。

基本情况

操作系统版本:CentOS release 5.6 64位

操作系统内存:8G

数据库版本:5.1.56-community 64位

数据库初始化参数:默认

数据库表和数据量

表a:

mysql> desc a2kw;+-------+-------------+------+-----+---------+-------+

| Field | Type        | Null | Key | Default | Extra |

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

| c1    | varchar(20) | YES  | MUL | NULL         |

| c2    | varchar(30) | YES     | NULL         |

| c3    | varchar(12) | YES     | NULL         |

| c4    | varchar(20) | YES     | NULL         |

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

4 rows in set (0.00 sec)

表b

mysql> desc b2kw;+-------+-------------+------+-----+---------+-------+

| Field | Type        | Null | Key | Default | Extra |

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

| c1    | varchar(20) | YES     | NULL         |

| c2    | varchar(30) | YES     | NULL         |

| c3    | varchar(12) | YES     | NULL         |

| c4    | varchar(20) | YES     | NULL         |

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

4 rows in set (0.00 sec)

 

a和b表的数据概况如下

mysql> select * from a2kw limit 10;+-----------+-----------+------+----------+

| c1        | c2        | c3   | c4       |

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

| 662164461 | 131545534 | TOM0 | 20120520 |

| 226662142 | 605685564 | TOM0 | 20120516 |

| 527008225 | 172557633 | TOM0 | 20120514 |

| 574408183 | 350897450 | TOM0 | 20120510 |

| 781619324 | 583989494 | TOM0 | 20120510 |

| 158872754 | 775676430 | TOM0 | 20120512 |

| 815875622 | 631631832 | TOM0 | 20120514 |

| 905943640 | 477433083 | TOM0 | 20120514 |

| 660790641 | 616774715 | TOM0 | 20120512 |

| 999083595 | 953186525 | TOM0 | 20120513 |

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

10 rows in set (0.01 sec)

基本步骤

1、在B表上创建索引

mysql> select count(*) from b2kw;+----------+

| count(*) |

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

| 20000002 |

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

1 row in set (0.00 sec)

mysql> create index ind_b2kw_c1 on  b2kw(c1);

Query OK, 20000002 rows affected (1 min 2.94 sec)

Records: 20000002  Duplicates: 0  Warnings: 0

数据量为:20000002 ,时间为:1 min 2.94 sec

2、把a、b分别插入中间表temp表中

创建中间表mysql> create table temp  select * from c2kw where 1=2;

Query OK, 0 rows affected (0.00 sec)

Records: 0  Duplicates: 0  Warnings: 0

插入数据

mysql> insert into temp  select * from a2kw;

Query OK, 20000002 rows affected (13.23 sec)

Records: 20000002  Duplicates: 0  Warnings: 0

mysql> insert into temp  select * from b2kw;

Query OK, 20000002 rows affected (13.27 sec)

Records: 20000002  Duplicates: 0  Warnings: 0

mysql> select count(*) from temp;

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

| count(*) |

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

| 40000004 |

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

1 row in set (0.00 sec)

数据量为:40000004 ,时间为:26.50 sec

3、temp建立联合索引,强制索引去掉重复数据

mysql> create index ind_temp_c123 on temp(c1,c2,c3);Query OK, 40000004 rows affected (3 min 43.87 sec)

Records: 40000004  Duplicates: 0  Warnings: 0

查看执行计划

mysql> explain select c1,c2,c3,max(c4) from temp FORCE INDEX (ind_temp_c123) group by c1,c2,c3 ;

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

| id | select_type | table | type  | possible_keys | key           | key_len | ref  | rows     | Extra |

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

1 | SIMPLE      | temp  | index | NULL          | ind_temp_c123 | 71      | NULL | 40000004 |       |

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

1 row in set (0.05 sec)

mysql> insert into c2kw select c1,c2,c3,max(c4) from temp FORCE INDEX (ind_temp_c123) group by c1,c2,c3 ;

Query OK, 20000004 rows affected (2 min 0.85 sec)

Records: 20000004  Duplicates: 0  Warnings: 0

实际大约花费实际为:6 min

4、删除中间表

mysql> drop table temp;Query OK, 0 rows affected (0.99 sec)

实际大约花费实际为:1 sec

5、建立c索引

mysql> create index ind_c2kw_c1 on c2kw(c1);Query OK, 20000004 rows affected (49.74 sec)

Records: 20000004  Duplicates: 0  Warnings: 0

mysql> create index ind_c2kw_c2 on c2kw(c2);

Query OK, 20000004 rows affected (1 min 47.20 sec)

Records: 20000004  Duplicates: 0  Warnings: 0

mysql> create index ind_c2kw_c3 on c2kw(c3);

Query OK, 20000004 rows affected (2 min 42.02 sec)

Records: 20000004  Duplicates: 0  Warnings: 0

实际大约花费实际为:5分钟

6、清空a、b表

mysql> truncate table a2kw;Query OK, 0 rows affected (1.15 sec)

mysql> truncate table b2kw;

Query OK, 0 rows affected (1.34 sec)

实际大约花费实际为:3sec

一共花费的时间大概在15分钟左右

转自:http://blog.sina.com.cn/s/blog_5755b8ed0101err7.html

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