Antecedents

Because we need to write a unified file management platform , File upload is required , download , Preview and other functions ,Mysql Realize the storage of files . Use QT Development UI function . And successfully upload the file （size<4）; At present, it is not found or known when the file is larger than 4M when mysql Will report a mistake

Online test

Because the files uploaded by your own test are bytes or kb size ; Can upload successfully Mysql, No other considerations .
After online , It will prompt that the file upload failed , Then check the error prompt ：

QSqlError("2013", "QMYSQL3: Unable to execute statement", "Lost connection to MySQL server during query")

error , Server Disconnected ,

analysis

Because there are successful upload examples , It's definitely not a code problem , see mysql To configure , Query response time , Maximum query data , The default is 4M, The tested file is larger than 4M There will be an error , So you need to modify the configuration file ,

solve

mysql Install directory or search the system disk for element files my.ini And open ,
Add the statement ：
# Size customization
max_allowed_packet=16M

Location

So where should the statement be placed in the configuration file ,
[mysql] after
or
[mysqld] after
In both places And restart Mysql service , It turned out to be a failure ,
Finally, please max_allowed_packet The statement is stored at the end of the configuration file , Restart the service to upload