mysql主库清理数据，从库保留

2022-02-07 10:54:51

因为业务需要，想在mysql主库清理一些数据，但从库想要保留，根据网友介绍，可以根据binlog跳过清理的命令

1.确保主从同步的情况下，主库开始操作
mysql> flush logs;                    --刷新日志，切换一个新的binlog日志，比较小，后面修改就会方便些
Query OK, 0 rows affected (0.21 sec)

mysql> show master status \G
*************************** 1. row ***************************
             File: mysql-bin.000039    --这里的binlog位置后面不会用到
         Position: 33958
     Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set:
1 row in set (0.03 sec)

2.从库停止同步    ---第1.2步尽量要快速操作
mysql> stop slave;
Query OK, 0 rows affected (0.05 sec)

mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.1.196
                  Master_User: repli
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000039
          Read_Master_Log_Pos: 488906
               Relay_Log_File: mysql-relay-bin.000016
                Relay_Log_Pos: 489119
        Relay_Master_Log_File: mysql-bin.000039
             Slave_IO_Running: No
            Slave_SQL_Running: No

3.主库清空数据

mysql> truncate table t2;   步骤a
Query OK, 0 rows affected (0.46 sec)

mysql> show master status \g 步骤b
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000039 | 1942762 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.06 sec)

/usr/local/mysql/bin/mysqlbinlog mysql-bin.000039 >000039.sql   步骤c

4.编辑000039.sql，删掉truncate语句
truncate table t2 /*!*/;   ---删掉的内容

查找1942762 找不到该位置的话，可能会丢失数据，因此前面的三步abc一定要注意顺序！最好sql里面是包含这个位置信息的，然后删掉后面的内容，避免后面日志应用的时候，重复操作。

end_log_pos 1942762   将这个位置后面的内容全部干掉！

5.从库恢复
/usr/local/mysql/bin/mysql -umydba -p
source /root/000039.sql
mysql> change master to master_log_file='mysql-bin.000039',master_log_pos=1942762;
Query OK, 0 rows affected (0.19 sec)

mysql> start slave;
Query OK, 0 rows affected (0.01 sec)

mysql> show slave status \G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.196
                  Master_User: repli
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000039
          Read_Master_Log_Pos: 10009221
               Relay_Log_File: mysql-relay-bin.000002
                Relay_Log_Pos: 8066779
        Relay_Master_Log_File: mysql-bin.000039
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB:
           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: 10009221
              Relay_Log_Space: 8066986
              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: 1
                  Master_UUID: 701cbadc-ba33-11e5-9091-305a3a78baf2
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           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
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.00 sec)

---主从同步，跳过了truncate这个命令

6.验证
主库：
mysql> select * from t2;
Empty set (0.00 sec)

从库：
mysql> select * from t2;
+----+
| id |
+----+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
+----+
5 rows in set (0.00 sec)

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