mysql操作命令梳理（3）-pager

在mysql日常操作中，妙用pager设置显示方式，可以大大提高工作效率。比如select出来的结果集超过几个屏幕，那么前面的结果一晃而过无法看到，这时候使用pager可以设置调用os的more或者less等显示查询结果，和在os中使用more或者less查看大文件的效果一样。

pager用法：
实际上等于将它设置以后的所有mysql操作命令的输出通过pager设置命令执行，类似于管道符的作用

nopager命令：取消pager设置，恢复之前的输出状态。（如果不设置nopager，那么只能通过重启mysql服务才能恢复了）

举些例子来说明吧：
1）当处理大量数据时，不想显示查询的结果，而只需知道查询花费的时间。

mysql> select * from huanqiu.haha;
+----+------------+
| id | name       |
+----+------------+
|  1 | wangshibo  |
|  2 | wangshikui |
|  3 | wangjuan   |
|  4 | wangman    |
| 11 | wangshikui |
+----+------------+
5 rows in set (0.00 sec)
mysql> pager cat /dev/null;        //实际上等于后面执行的命令|cat /dev/null，这样显示结果就只是执行时间了
PAGER set to 'cat /dev/null'
mysql> select * from huanqiu.haha;
5 rows in set (0.00 sec)
mysql> nopager;                   //恢复之前的输出状态
PAGER set to stdout
mysql> select * from huanqiu.haha;
+----+------------+
| id | name       |
+----+------------+
|  1 | wangshibo  |
|  2 | wangshikui |
|  3 | wangjuan   |
|  4 | wangman    |
| 11 | wangshikui |
+----+------------+
5 rows in set (0.00 sec)

2）如果有大量连接，用show processlist看不方便，想看有多少Sleep状态，则可以用pager。

mysql> show processlist;
+------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+
| Id   | User  | Host                | db     | Command     | Time | State                                                                 | Info             |
+------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+
|    5 | root  | localhost           | huanpc | Query       |    0 | init                                                                  | show processlist |
| 1801 | slave | 192.168.1.102:37125 | NULL   | Binlog Dump | 9904 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL             |
+------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+
2 rows in set (0.00 sec)

mysql> pager grep Sleep |wc -l;
PAGER set to 'grep Sleep |wc -l'
mysql> show processlist;           //类似于show processlist结果再通过grep Sleep |wc -l显示；下面表示一共有2个连接，其中0个Sleep状态的连接。
0
2 rows in set (0.00 sec)
mysql> nopager;                    //恢复之前的输出状态

3）设置pager，只查看slave状态的几个status值。

mysql> show slave status \G;              //其中的\G表示显示要换行显示
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.101
                  Master_User: slave
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 5370489
               Relay_Log_File: mysql-relay-bin.000005
                Relay_Log_Pos: 2476520
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: huanqiu,huanpc
          Replicate_Ignore_DB: mysql
           Replicate_Do_Table:
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table:
  Replicate_Wild_Ignore_Table:
                   Last_Errno: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 5370489
              Relay_Log_Space: 2476693
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 101
                  Master_UUID: b667a58f-d6e0-11e6-8c0a-fa163e2d66ac
             Master_Info_File: /data/mysql/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 0
1 row in set (0.00 sec)

ERROR:
No query specified

mysql> pager cat | egrep -i 'system user|Exec_Master_Log_Pos|Seconds_Behind_Master|Read_Master_Log_Pos';
PAGER set to 'cat | egrep -i 'system user|Exec_Master_Log_Pos|Seconds_Behind_Master|Read_Master_Log_Pos''

mysql> show slave status \G;
          Read_Master_Log_Pos: 5370489
          Exec_Master_Log_Pos: 5370489
        Seconds_Behind_Master: 0
1 row in set (0.00 sec)

ERROR:
No query specified

mysql> nopager;                 //恢复之前的显示状态
PAGER set to stdout