JQuery遍历控件的方法

MySQL导出的SQL语句在导入时有可能会非常非常慢，在处理百万级数据的时候，可能导入要花几小时。在导出时合理使用几个参数，可以大大加快导 入的速度。

-e 使用包括几个VALUES列表的多行INSERT语法;

--max_allowed_packet=XXX 客户端/服务器之间通信的缓存区的最大大小;

--net_buffer_length=XXX TCP/IP和套接字通信缓冲区大小,创建长度达net_buffer_length的行。

注意：max_allowed_packet 和 net_buffer_length 不能比目标数据库的设定数值 大，否则可能出错。

首先确定目标数据库的参数值

mysql> show variables like 'max_allowed_packet';

mysql> show variables like 'net_buffer_length';

根据参数值书写 mysqldump 命令，如：

# mysqldump -uroot -p dbhost -e --max_allowed_packet=16777216 --net_buffer_length=16384 > dbhost.sql

OK，现在速度就很快了，主要注意的是导入和导出端的 max_allowed_packet 和 net_buffer_length 这2个参数值设定，弄大点就OK了

其实，最快的方法，是直接COPY数据库目录，不过记得先停止 MySQL 服务。

测试导出

bblaishu数据库大小740M

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 16384 |

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

1 row in set (0.00 sec)

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 1047552 |

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

1 row in set (0.00 sec)

time mysqldump -uroot -p`cat /data/save/mysql_root` -T/data/test/test bblaishu -e --max_allowed_packet=1047552 --net_buffer_length=16384

real 0m14.183s

user 0m0.005s

sys 0m0.003s

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 65536 |

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

1 row in set (0.00 sec)

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 2096128 |

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

1 row in set (0.00 sec)

time mysqldump -uroot -p`cat /data/save/mysql_root` -T/data/test/test bblaishu -e --max_allowed_packet=2096128 --net_buffer_length=65536

real 1m8.397s

user 0m0.007s

sys 0m0.008s

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 2096128 |

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

1 row in set (0.01 sec)

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 16384 |

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

1 row in set (0.00 sec)

time mysqldump -uroot -p`cat /data/save/mysql_root` -T/data/test/test bblaishu -e --max_allowed_packet=2096128 --net_buffer_length=16384

real 0m12.997s

user 0m0.004s

sys 0m0.007s

结论：在将数据库导出的时候net_buffer_length默认就好，max_allowed_packet建议设置大一点，测试设置2M比较合适

测试导入

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 16384 |

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

1 row in set (0.00 sec)

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 1047552 |

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

1 row in set (0.00 sec)

time mysqlimport --local -l -uroot -p`cat /data/save/mysql_root` bblaishu `find ./ -name "*.txt"`

real 1m31.587s

user 0m0.115s

sys 0m0.409s

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 2096128 |

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

1 row in set (0.00 sec)

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 65536 |

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

1 row in set (0.00 sec)

time mysqlimport --local -l -uroot -p`cat /data/save/mysql_root` bblaishu `find ./ -name "*.txt"`

real 1m31.524s

user 0m0.122s

sys 0m0.355s

mysql> show variables like 'max_allowed_packet';

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

| Variable_name | Value |

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

| max_allowed_packet | 2096128 |

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

1 row in set (0.00 sec)

mysql> show variables like 'net_buffer_length';

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

| Variable_name | Value |

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

| net_buffer_length | 16384 |

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

1 row in set (0.00 sec)

time mysqlimport --local -l -uroot -p`cat /data/save/mysql_root` bblaishu `find ./ -name "*.txt"`

real 1m32.959s

user 0m0.123s

sys 0m0.429s

结论：在导入的时候同样net_buffer_length默认就好，max_allowed_packet建议设置为2M

本文出自 “一直很安静” 博客，请务必保留此出处http://scoke.blog.51cto.com/769125/502896