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QSqlDatabase connection issue

  • Hi! I have the application witch requires connection to Database on the server. It all works well but after 4 minutes of inactivity of DB connection it displays errors.


    I know the problem is with wait_timeout variable on DB server but I can't change it because I don't have permission to the server. On the server it has value of 240 seconds = 4 minutes.

    I have added some check to execute query and it will check connection:


    void Test::dbTest()
        QSqlQuery sqlQuery("some query", QSqlDatabase::database("ConnectionName"));
        if (sqlQuery.size() > 0) {
           // Some action
        } else {
            int errorCode = sqlQuery.lastError().number();
            if (errorCode == 2013) {
                QSqlDatabase::database("ConnectionName").open(); // opens DB connection
                dbTest(); // runs recursively
            } else {
                qDebug() << sqlQuery.lastError().text();

    It fixes such situation but I need to add such check for all functions that works with DB. But what if I can omit such check and everywhere just run QSqlDatabase::open() before query? What will happen when connection is still alive and QSqlDatabase::open() function will run again, it will create another connection or use existing? Thanks.

  • Lifetime Qt Champion


    What about using a heartbeat on that connection ?

  • @SGaist

    Yes, it also will work. But I have checked QSqlDatabase::open() solution on WAMP and it creates only 1 connection to DB. Thanks.

  • Lifetime Qt Champion

    You should take a look at the QSqlDatabase::setConnectOptions and the specifics for MySQL. You could fine tune the timeout for your server.

  • @SGaist

    I have added setConnectOptions("MYSQL_OPT_RECONNECT=TRUE"); and now it automatically reconnects. Thanks.

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