QSqlDatabase: QMYSQL driver not loaded on Ubuntu 15.04 64bits

Question

In Ubuntu 15.04 64 bits I installed Qt5.6 (online installer) and while trying to move my development environment from Windows 7 to Linux I faced the following:

SqlDatabase: QMYSQL driver not loaded

Following this, I managed to find ~/Qt/5.6/gcc_64/plugins/sqldrivers/libqsqlmysql.so and then:

$ ldd libqsqlmysql.so
    linux-vdso.so.1 =>  (0x00007ffffd571000)
    libmysqlclient_r.so.16 => not found
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fe94ef24000)
    libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007fe94ecec000)
    libnsl.so.1 => /lib/x86_64-linux-gnu/libnsl.so.1 (0x00007fe94ead2000)
    libssl.so.10 => not found
    libcrypto.so.10 => not found
    libQt5Sql.so.5 => /home/user/Qt/5.6/gcc_64/plugins/sqldrivers/../../lib/libQt5Sql.so.5 (0x00007fe94e88d000)
    libQt5Core.so.5 => /home/user/Qt/5.6/gcc_64/plugins/sqldrivers/../../lib/libQt5Core.so.5 (0x00007fe94e17a000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fe94df5c000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fe94dc4d000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fe94d944000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fe94d72e000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe94d364000)
    libicui18n.so.56 => /home/user/Qt/5.6/gcc_64/plugins/sqldrivers/../../lib/libicui18n.so.56 (0x00007fe94cec9000)
    libicuuc.so.56 => /home/user/Qt/5.6/gcc_64/plugins/sqldrivers/../../lib/libicuuc.so.56 (0x00007fe94cb11000)
    libicudata.so.56 => /home/user/Qt/5.6/gcc_64/plugins/sqldrivers/../../lib/libicudata.so.56 (0x00007fe94b12e000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fe94af29000)
    libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007fe94ad27000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fe94ab1f000)
    libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fe94a80f000)
    /lib64/ld-linux-x86-64.so.2 (0x000056024837f000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007fe94a5a2000)

Tells libmysqlclient_r.so.16 => not found. In fact, it seems I have a newer version:

find / -name libmysqlclient_r*
/usr/lib/x86_64-linux-gnu/libmysqlclient_r.so.18
/usr/lib/x86_64-linux-gnu/libmysqlclient_r.so.18.1.0
/usr/lib/x86_64-linux-gnu/libmysqlclient_r.so
/usr/lib/x86_64-linux-gnu/libmysqlclient_r.a

Perhaps that's the problem. Could some one confirm? How should I proceed?

Answer 1

First and foremost, double check that you have the packages containing libssl.so, libcrypto.so and libmysqlclient_r.so installed (looks like you have this last one, it's extremely likely you also have the first two, but just double check).

Then, your problem is that you have those shared objects with a different SONAME, sign that they're binary incompatible with the plugin shipped with Qt, which therefore needs to be recompiled.

Therefore:

1. install the development versions of the packages found above (libssl-dev, mysql-client-dev or similar).

2. run the MaintenanceTool from your Qt installation, and be sure to select to install Qt's source code too.

3. Go in QTDIR/5.6/Src/qtbase/src/plugins/sqldrivers/mysql/.

4. Run the right qmake, i.e. the one coming from that installation of Qt (not the system wide one or similar). Best way to be sure is providing the full path to it: QTDIR/5.6/gcc_64/bin/qmake.

5. Run make. Hopefully this will just work™; if it complains about some missing libraries, install them and rerun make.

6. This should now have produced a new libqsqlmysql.so plugin; overwrite the old one with this new one.

Answer 2

I also have the same problem with Qt5.11.1 and my OS is Ubuntu16.04 and I have resolve the problem by installing libmysqlclient18 from here

https://launchpad.net/ubuntu/xenial/amd64/libmysqlclient18/5.6.25-0ubuntu1

After download run the command from download directory,

sudo dpkg -i libmysqlclient18_5.6.25-0ubuntu1_amd64.deb

Answer 3

There are two fixes for this issue. First try and locate the qtbase folder located within your qt directory and try run ./configure -plugin-sql-mysql which will activate the driver if they're missing.

If this doesn't solve your issue, I suggest that you double check your code and try running one of the Qt examples which makes a connection to the Sql databases. I.e. modify the example code which connects to a local SQLite database changing the parameter to MySQL. If this example doesn't throw 'Driver not loaded error' then follow the step below.

Make sure you're using the static function of the QSqlDatabase i.e. rather than using

QSqlDatabase *db = new QSqlDatabase(); 
db->addDatabase("QMYSQL");  

you should be doing

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