提高MySQL 导入导出测试
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
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