因工作需要，需要匯入一個200M左右的sql到user庫

執行命令

mysql> use user
Database changed
mysql> source /tmp/user.sql

匯入的過程中出現MySQL server has gone away錯誤，資料匯入失敗。

錯誤資訊如下：

ERROR 2006 (HY000): MySQL server has gone away
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    11
 

Current database: user

ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    12
Current database: user

ERROR 2006 (HY000): MySQL server has gone away
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    13
Current database: user
 

開始以為是超時導致，因此調大了 connect_timeout 和 wait_timeout 的值。

重新執行後問題依舊。


解決方法：

檢視資料，發現了 max_allowed_packet 引數，
官方解釋是適當增大 max_allowed_packet 引數可以使client端到server端傳遞大資料時，系統能夠分配更多的擴充套件記憶體來處理。

檢視mysql max_allowed_packet的值

mysql> show global variables like 'max_allowed_packet';
+--------------------+---------+
 

| Variable_name      | Value   |
+--------------------+---------+
| max_allowed_packet | 4194304 |
+--------------------+---------+

可以看到是4M，然後調大為256M(1024*1024*256)

mysql> set global max_allowed_packet=268435456;
Query OK, 0 rows affected (0.00 sec)

mysql> show global variables like 'max_allowed_packet';
+--------------------+-----------+
| Variable_name      | Value     |
+--------------------+-----------+
| max_allowed_packet | 268435456 |
+--------------------+-----------+
1 row in set (0.00 sec)

修改後執行匯入，一切正常，解決問題。


注意：
使用set global命令修改 max_allowed_packet 的值，重啟mysql後會失效，還原為預設值。

如果想重啟後不還原，可以開啟 my.cnf 檔案，新增 max_allowed_packet = 256M 即可。