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c语言学习之结构篇代码示例-输入n个同学的姓名,数学英语成绩,按照平均分从低到高排序并输出

在虚拟机上测评了下MySQL 和 PostgreSQL 的各种LOAD FILE方式以及时间。 因为是虚拟机上的测评,所以时间只做参考,不要太较真, 看看就好了。
MySQL 工具:
    1. 自带mysqlimport工具。
    2. 命令行 load data infile ...
    3. 利用mysql-connector-python Driver来写的脚本。
 PostgreSQL 工具:
    1. pgloader 第三方工具。
    2. 命令行 copy ... from ...
    3. 利用psycopg2写的python 脚本。
测试表结构:

mysql> desc t1;
+----------+-----------+------+-----+-------------------+-------+
| Field    | Type      | Null | Key | Default           | Extra |
+----------+-----------+------+-----+-------------------+-------+
| id       | int(11)   | NO   | PRI | NULL              |       |
| rank     | int(11)   | NO   |     | NULL              |       |
| log_time | timestamp | YES  |     | CURRENT_TIMESTAMP |       |
+----------+-----------+------+-----+-------------------+-------+
3 rows in set (0.00 sec)
mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|  1000000 |
+----------+
1 row in set (6.80 sec)



测试CSV文件:
t1.csv 


MySQL 自身的loader: (时间24妙)


mysql> load data infile ‘/tmp/t1.csv‘ into table t1 fields terminated by ‘,‘ enclosed by ‘"‘ lines terminated by ‘\r\n‘; 
Query OK, 1000000 rows affected (24.21 sec)
Records: 1000000  Deleted: 0  Skipped: 0  Warnings: 0



MySQL python 脚本:(时间23秒)
>>> 
Running 23.289 Seconds



MySQL 自带mysqlimport:(时间23秒)
[root@mysql56-master ~]# time mysqlimport t_girl ‘/tmp/t1.csv‘ --fields-terminated-by=‘,‘ --fields-enclosed-by=‘"‘ --lines-terminated-by=‘\r\n‘ --use-threads=2 -uroot -proot
t_girl.t1: Records: 1000000  Deleted: 0  Skipped: 0  Warnings: 0


real    0m23.664s
user    0m0.016s
sys     0m0.037s



PostgreSQL 自身COPY:(时间7秒)
t_girl=# copy t1 from ‘/tmp/t1.csv‘ with delimiter ‘,‘;
COPY 1000000
Time: 7700.332 ms




Psycopg2 驱动copy_to方法:(时间6秒)
[root@postgresql-instance scripts]# python load_data.py 
Running 5.969 Seconds.




Pgloader 导入CSV:(时间33秒)
[root@postgresql-instance ytt]# pgloader commands.load      
                    table name       read   imported     errors            time


                        ytt.t1    1000000    1000000          0         33.514s
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
             Total import time    1000000    1000000          0         33.514s



Pgloader 直接从MySQL 拉数据:(时间51秒)
[root@postgresql-instance ytt]# pgloader commands.mysql 
                    table name       read   imported     errors            time


               fetch meta data          2          2          0          0.138s
------------------------------  ---------  ---------  ---------  --------------
                            t1    1000000    1000000          0         51.136s
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
             Total import time    1000000    1000000          0         51.274s




附上commands.load和commands.mysql

commands.load:
LOAD CSV  
   FROM ‘/tmp/ytt.csv‘ WITH ENCODING UTF-8
        (  
           id, rank, log_time  
        )  
   INTO postgresql://t_girl:t_girl@127.0.0.1:5432/t_girl?ytt.t1 
   WITH skip header = 0,  
        fields optionally enclosed by ‘"‘,  
        fields escaped by backslash-quote,  
        fields terminated by ‘,‘  
 
    SET work_mem to ‘32 MB‘, maintenance_work_mem to ‘64 MB‘; 


commands.mysql:
LOAD DATABASE  
     FROM mysql://python_user:python_user@192.168.1.131:3306/t_girl?t1
     INTO postgresql://t_girl:t_girl@127.0.0.1:5432/t_girl?ytt.t1
 
 with data only


  SET maintenance_work_mem to ‘64MB‘,  
      work_mem to ‘3MB‘,  
      search_path to ‘ytt‘;


附pgloader 手册:
http://pgloader.io/howto/pgloader.1.html