千万级别mysql合并表快速去重

mysql合并表去重

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