QSqlDatabase: QMYSQL driver not loaded

[Tas-sos]

I run ubuntu 14.04 and i installed Qt4 and Qt5. I have created and implemented a project in Qt5 ( specifically : Based on Qt 5.4.1 (GCC 4.6.1, 32 bit) ).

I try in my programm to make connection to a database ( ΜySql ) but I can not.

When I run this code:

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("myTEST_db");
    db.setUserName("root");
    db.setPassword("123456789");
    if (!db.open())
    {
      QMessageBox::critical(0, QObject::tr("Database Error"),
                db.lastError().text());
    }

I get this error :

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

When i run this code :

    QPluginLoader loader;
    loader.setFileName("/home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so");
    qDebug() << "PluginLoader worked =" << loader.load();
    qDebug() << "Plugin Loader error=" << loader.errorString();

    qDebug() << QCoreApplication::libraryPaths();
    QCoreApplication::addLibraryPath("/home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so");
    qDebug() << QSqlDatabase::drivers();

I get this error :

PluginLoader worked = false
Plugin Loader error= "Cannot load library /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so: (libmysqlclient_r.so.16: cannot open shared object file: No such file or directory)"
("/home/myuser/Qt/5.4/gcc/plugins", "/home/myuser/Qt TestProject/build-TestProject-Desktop_Qt_5_4_1_GCC_32bit-Debug")
("QSQLITE", "QPSQL", "QPSQL7")

I can not understand what is happening, please very much you can help me?
I stress that I have installed and QT4 (maybe somewhere confused).

Thank you in advance.

[jsulm]

Did you check that /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so really exists? Is it 32bit?
One note: if you add a directory to library path then do not pass the file name! It must be a directory.

[Tas-sos]

@jsulm Firstly thank you very much friend for so prompt reply.
Yes I have 32-bit.

As for the file:

ls Qt/5.4/gcc/plugins/sqldrivers/
libqsqlite.so  libqsqlmysql.so  libqsqlpsql.so

one more effort:

    qDebug() << QCoreApplication::libraryPaths();
    QCoreApplication::addLibraryPath("/home/myuser/Qt/5.4/gcc/plugins/sqldrivers/");
    qDebug() << QSqlDatabase::drivers();


    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("myTEST_db");
    db.setUserName("root");
    db.setPassword("123456789");
    if (!db.open())
    {
      QMessageBox::critical(0, QObject::tr("Database Error"),
                db.lastError().text());

Error :

("/home/myuser/Qt/5.4/gcc/plugins", "/home/myuser/Qt TestProject/build-TestProject-Desktop_Qt_5_4_1_GCC_32bit-Debug")
("QSQLITE", "QMYSQL", "QMYSQL3", "QPSQL", "QPSQL7")
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

[SGaist]

Hi,

Do you have the MySQL client libraries installed on your system ?

[Tas-sos]

@SGaist If i do not do wrong , yes.
Extra now again I ran :

sudo apt-get install mysql-client
sudo apt-get install libmysqlclient-dev
sudo apt-get install libqt5sql5-mysql
sudo apt-get install libmysqlclient16-dev
sudo apt-get install libmysql++-dev

Because I despaired, that I have found of libraries i have installing.

But absolutely nothing. I did not expect to be so hard. :(

[SGaist]

Can you run ldd on Qt's MySQL plugin ?

[Tas-sos]

@SGaist
this is what you mean;

:~/Qt/5.4/gcc/plugins/sqldrivers$ ldd libqsqlmysql.so
	linux-gate.so.1 =>  (0xb76e3000)
	libmysqlclient_r.so.16 => not found
	libQt5Sql.so.5 => /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0xb7672000)
	libQt5Core.so.5 => /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0xb712d000)
	libstdc++.so.6 => /usr/lib/i386-linux-gnu/libstdc++.so.6 (0xb702b000)
	libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb6e7d000)
	libpthread.so.0 => /lib/i386-linux-gnu/libpthread.so.0 (0xb6e61000)
	libicui18n.so.53 => /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/./../../lib/libicui18n.so.53 (0xb6c0a000)
	libicuuc.so.53 => /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/./../../lib/libicuuc.so.53 (0xb6a8a000)
	libdl.so.2 => /lib/i386-linux-gnu/libdl.so.2 (0xb6a85000)
	libgthread-2.0.so.0 => /usr/lib/i386-linux-gnu/libgthread-2.0.so.0 (0xb6a82000)
	librt.so.1 => /lib/i386-linux-gnu/librt.so.1 (0xb6a79000)
	libglib-2.0.so.0 => /lib/i386-linux-gnu/libglib-2.0.so.0 (0xb696d000)
	libm.so.6 => /lib/i386-linux-gnu/libm.so.6 (0xb6926000)
	libgcc_s.so.1 => /lib/i386-linux-gnu/libgcc_s.so.1 (0xb6908000)
	/lib/ld-linux.so.2 (0xb76e4000)
	libicudata.so.53 => /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/./../../lib/libicudata.so.53 (0xb547f000)
	libpcre.so.3 => /lib/i386-linux-gnu/libpcre.so.3 (0xb5441000)

I entered the forum to tell you , this problem have just i found. xaxa and I see that what you ask (if i do not do wrong)

[jsulm]

That's probably the problem:
libmysqlclient_r.so.16 => not found

It looks like the MySQL lib is not installed.

[Tas-sos]

what can I do to fix it?

[jsulm]

Can you check whether you have libmysqlclient_r.so.16 on your system?
On my Ubuntu 14.04 it is libmysqlclient_r.so.18

[Tas-sos]

@jsulm
Yes I have the same too :

:/usr/lib/i386-linux-gnu$ ls | grep libmysql
libmysqlclient.a
libmysqlclient_r.a
libmysqlclient_r.so
libmysqlclient_r.so.18
libmysqlclient_r.so.18.0.0
libmysqlclient.so
libmysqlclient.so.18
libmysqlclient.so.18.0.0

[SGaist]

Then the easiest way is to rebuild the plugin against your installed MySQL client libraries. It's described here

[Tas-sos]

@SGaist
Could someone please guide me?
This guide does not help that much.. :/

There is no other way?

[hskoglund]

Hi, you could try to trick Qt you've got the correct file, by using the newer version as the older one (just a guess :-):
cp libmysqlclient_r.so.18.0.0 libmysqlclient_r.so.16

[Tas-sos]

@hskoglund
I tried to shortcut and copy as you say now.
but the same effect :

code :

    QPluginLoader loader;
    loader.setFileName("/home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so");
    qDebug() << "PluginLoader worked =" << loader.load();
    qDebug() << "Plugin Loader error=" << loader.errorString();

error :

PluginLoader worked = false
Plugin Loader error= "Cannot load library /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so: (/usr/lib/i386-linux-gnu/libmysqlclient_r.so.16: version `libmysqlclient_16' not found (required by /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so))"

[hskoglund]

Ok, maybe you need to go further tricking Qt also that the libmysqlclient.so.16 is fine and well, by also copying that file:
cp libmysqlclient.so.18.0.0 libmysqlclient.so.16

[Tas-sos]

@hskoglund
oops you're right! I had not noticed the name. But now? I have this error :

PluginLoader worked = false
Plugin Loader error= "Cannot load library /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so: (/usr/lib/i386-linux-gnu/libmysqlclient_r.so.16: version `libmysqlclient_16' not found (required by /home/myuser/Qt/5.4/gcc/plugins/sqldrivers/libqsqlmysql.so))"

and these files :

:/usr/lib/i386-linux-gnu$ ls | grep libmysql
libmysqlclient.a
libmysqlclient_r.a
libmysqlclient_r.so
libmysqlclient_r.so.16
libmysqlclient_r.so.18
libmysqlclient_r.so.18.0.0
libmysqlclient.so
libmysqlclient.so.16
libmysqlclient.so.18
libmysqlclient.so.18.0.0

[hskoglund]

Ahhh, sorry it seems the ruse didn't work all the way :-(
It's probably a version resource or something simular in the libmysqlclient.so.18.0.0 file that says "version 18" and not "version 16".

Anyway I think your next step is instead to try to download and install the kosher *.16, have you tried?
sudo apt-get install libmysqlclient16

[SGaist]

You can't cheat like that on Linux ;)

@Tas-sos what trouble did you have to rebuild the plugin ? It's really just grab Qt's source and follow the lines of the documentation.

[Tas-sos]

@hskoglund

Never mind my friend anyway thank you very much!
Yes I have tried it and got this:

E: Unable to locate the package libmysqlclient16

or this :

E: Unable to locate the package libmysqlclient16-dev

@SGaist
xaxaax my friend like your answer.
"You can't cheat like that on Linux ;)"

As for the guide (documentation) , basically confuses me a little and I do not know if I can follow him because for example he says to run this command :

cd $QTDIR/qtbase/src/plugins/sqldrivers/mysql

But me the file structure is :

:~$ ls Qt 
5.4
components.xml
Docs
Examples
Extras
InstallationLog.txt
Licenses
MaintenanceTool
MaintenanceTool.dat
MaintenanceTool.ini
network.xml
Tools

:~/Qt/5.4$ ls
android_armv7  gcc

:~/Qt/5.4/gcc$ ls
bin
icudtl.dat
imports
include
lib
libexec
mkspecs
phrasebooks
plugins
qml
qtwebengine_resources.pak
translations

:~/Qt/5.4/gcc/plugins$ ls -l

audio
bearer
designer
generic
geoservices
iconengines
imageformats
mediaservice
platforminputcontexts
platforms
platformthemes
playlistformats
position
printsupport
qml1tooling
qmltooling
qtwebengine
sensorgestures
sensors
sqldrivers  <-----------

:~/Qt/5.4/gcc/plugins$ tree sqldrivers/
sqldrivers/
├── libqsqlite.so
├── libqsqlmysql.so
└── libqsqlpsql.so

the path that says, to me (as you see) does not exist. :/
Extra searches:

find  ~/Qt -name "sqldrivers"
/home/myuser/Qt/Tools/QtCreator/bin/plugins/sqldrivers
/home/myuser/Qt/5.4/gcc/plugins/sqldrivers

$find  ~/Qt -name "qtbase"
-nothing-

$ find  ~/Qt -name "mysql"
-nothing-

In my system the folders with name "mysql" are only those :

sudo find  / -name "mysql"
/var/lib/mysql
/var/lib/mysql/mysql
/var/log/mysql
/etc/apparmor.d/abstractions/mysql
/etc/init.d/mysql
/etc/mysql
/usr/bin/mysql
/usr/lib/perl5/auto/DBD/mysql
/usr/lib/perl5/DBD/mysql
/usr/lib/mysql
/usr/share/maven-repo/mysql
/usr/share/mysql
/usr/share/bash-completion/completions/mysql
/usr/include/mysql
/usr/include/mysql/mysql

and folder named "qtbase" does not exist.
For this reason the documentation does not help.