MYSQL driver not loaded when using mariadb on Debian Linux

tataDanAz · wrote on 27 Aug 2020, 03:09

I am using Debian 10 (which by default comes with mariadb instead of mysql. I have the mariadb 10.3 client and 10.3 server installed and functioning. I installed QT 5.11.3 using the apt install command. My version of QT Creator is 4.8.2.
The relevant code that I am using is:```
void MainWindow::on_pushButton_clicked()
{
QSqlDatabase db = QSqlDatabase::addDatabase("MYSQL");
db.setHostName("127.0.0.1");
db.setUserName("root");
db.setPassword("");
db.setDatabaseName("nation");

if (db.open()) {
    QMessageBox::information(this, "Connection", "Database Connected Successfully");
} else{
    QMessageBox::information(this, "Not Connected", "Database Is Not Connected");
}

}

The error that I get is :```
QSqlDatabase: MYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3

Any assistance in this matter would be appreciated.

Bonnie · wrote on 27 Aug 2020, 03:47

I guess mariadb doesn't have libmysqlclient.so which is needed by the old pre-compiled mysql plugin?
You can set QT_DEBUG_PLUGINS environment variable to 1 and check the diagnostic information from output.

tataDanAz · 27 Aug 2020, 04:57

libmysqlclient.so is in /usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers, but it did not come the standard debian installation. I think it came from a ubuntu .deb file. Here is an extract of the output when application with QT_DEBUG_PLUGINS=1:

code_QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libmysqlclient.so"
"Failed to extract plugin meta data from '/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libmysqlclient.so'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlite.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlite.so, metadata=
{
    "IID": "org.qt-project.Qt.QSqlDriverFactoryInterface",
    "MetaData": {
        "Keys": [
            "QSQLITE"
        ]
    },
    "className": "QSQLiteDriverPlugin",
    "debug": false,
    "version": 330499
}


Got keys from plugin meta data ("QSQLITE")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlmysql.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlmysql.so, metadata=
{
    "IID": "org.qt-project.Qt.QSqlDriverFactoryInterface",
    "MetaData": {
        "Keys": [
            "QMYSQL3",
            "QMYSQL"
        ]
    },
    "className": "QMYSQLDriverPlugin",
    "debug": false,
    "version": 330499
}


Got keys from plugin meta data ("QMYSQL3", "QMYSQL")
QFactoryLoader::QFactoryLoader() checking directory path "/home/daniel/qtProjects/build-qt5database-Desktop-Debug/sqldrivers" ...text

The most important piece of the output is:

"Failed to extract plugin meta data from '/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libmysqlclient.so'" 
         not a plugin

Is it possible to find a valid version of libmysqlclient.so?

jsulm · wrote on 27 Aug 2020, 04:57

@tataDanAz said in MYSQL driver not loaded when using mariadb on Debian Linux:

libmysqlclient.so

This is NOT Qt plug-in for MySql! This is the client library from MySql/MariaDB. Why is this file in /usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers?!
The correct file name of the plug-in should be libqsqlmysq.so

Please search for MySQL in this forum: this is asked many many times and was answered many times.

Bonnie · wrote on 27 Aug 2020, 04:57

@tataDanAz
No, it is not the most important piece, just because libmysqlclient.so is not supposed to be put in the plugin folder.
I think you should move it to the qt bin folder.
The most important piece should be about libqsqlmysql.so.
Is it loaded successfully? If not, what's the information?

tataDanAz · wrote on 27 Aug 2020, 20:16

@Bonnie said in MYSQL driver not loaded when using mariadb on Debian Linux:

QT_DEBUG_PLUGINS

Apparently in Debian libmysqlclient.so is a symbolic link to libmariadbclient.so (at least that's what my limited understanding leads me to believe).
I copied both files from /usr/lib/x86_64-linux-gnu to /usr/lib/x86_64-linux-gnu/qt5/bin, but I still get the error. (I also tried copying them to /usr/lib/qt5/bin and the directory when my application resides, but that did not work either).
As far as I can tell, libqsqlmysql.so loaded successfully. Here is the latest extract from the output:

QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlmysql.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/sqldrivers/libqsqlmysql.so, metadata=
{
    "IID": "org.qt-project.Qt.QSqlDriverFactoryInterface",
    "MetaData": {
        "Keys": [
            "QMYSQL3",
            "QMYSQL"
        ]
    },
    "className": "QMYSQLDriverPlugin",
    "debug": false,
    "version": 330499
}

Got keys from plugin meta data ("QMYSQL3", "QMYSQL")

QFactoryLoader::QFactoryLoader() checking directory path "/home/daniel/qtProjects/build-qt5database-Desktop-Debug/sqldrivers" ...
QSqlDatabase: MYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3

tataDanAz · wrote on 27 Aug 2020, 21:05

I finally discovered the problem. It was a problem in my code.
Instead of writing

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");

I wrote

QSqlDatabase db = QSqlDatabase::addDatabase("MYSQL");

I was attempting to enter the code from a youtube video and I left out a "Q".
Thanks to all who attempted to help me. I hope that I didn't cause anybody too much difficulty in trying to help me.