Unable to use PostgreSQL with Qt 5.2.1

bhaskar2014

Even after reading related topics in the forum, and the details given in http://qt-project.org/doc/qt-5/sql-driver.html I am still unable to get a simple Qt desktop dialog application to work with PostgreSQL in Windows 7 64-bit. I am able to compile the application, but when I run it (from within Qt Creator), it is not loading the database driver and I am getting the following error (please note that I have the environment variable QT_DEBUG_PLUGINS set to 1).

_QFactoryLoader::QFactoryLoader() looking at "C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.dll"
Found metadata in lib C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.dll, metadata=
{
"IID": "org.qt-project.Qt.QSqlDriverFactoryInterface",
"MetaData": {
"Keys": [
"QPSQL7",
"QPSQL"
]
},
"className": "QPSQLDriverPlugin",
"debug": true,
"version": 328193
}

Got keys from plugin meta data ("QPSQL7", "QPSQL")
QFactoryLoader::QFactoryLoader() looking at "C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.pdb"
"Plugin verification data mismatch in 'C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.pdb'"
not a plugin
QFactoryLoader::QFactoryLoader() checking directory path "C:/Users/testuser/qtwork/build-TestApp-Desktop_Qt_5_2_1_MSVC2012_OpenGL_64bit-Debug/debug/sqldrivers" ...
loaded library "C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.dll"
QLibraryPrivate::loadPlugin failed on "C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.dll" : "Cannot load library C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/sqldrivers/qsqlpsqld.dll: "
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7
QFactoryLoader::QFactoryLoader() checking directory path "C:/bin/Qt/Qt5.2.1/5.2.1/msvc2012_64_opengl/plugins/accessiblebridge" ... _

The location of PostgreSQL library libpq.dll, C:\Program Files\PostgreSQL\9.3\bin, has been appended to the PATH variable.

This is what I am using:

(1) Qt Creater 3.0.1
(2) Qt 5.2.1 MSVC2012 OpenGL 64bit
(3) PostgreSQL 9.3 64-bit
(4) Windows 7 64-bit
(5) Microsoft Visual C++ Compiler 11.0

The code snippet is quite simple, taken from the documentation pages.

QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
//db.setHostName("localhost");
db.setDatabaseName("mydb");
db.setUserName("postgres");
db.setPassword("postgres");
bool ok = db.open();

if (ok == false) {
QSqlError error = db.lastError();
// printing the error here
}

The following is my project file:
_#-------------------------------------------------

Project created by QtCreator 2014-03-31T09:51:40

#-------------------------------------------------

QT += core gui sql

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = TestApp
TEMPLATE = app

SOURCES += main.cpp
dialog.cpp

HEADERS += dialog.h

FORMS += dialog.ui

LIBS += -LC:\Program Files\PostgreSQL\9.3\lib
LIBS += -llibpq_

Any help or hint to resolve this would be highly appreciated.

SGaist

Hi and welcome to devnet,

Check that the PATH environment variable in the Run part of the Project panel also contains the path to the PostgreSQL dll

Hope it helps

bhaskar2014

Hello SGalst, thank you for the reply.

Yes the path to PostgreSQL dll, C:\Program Files\PostgreSQL\9.3\bin, is already appended to the PATH env. variable in the Run part of the Project panel.

bhaskar2014

Solved after using Dependency Walker to look at qsqlpsqld.dll.

Think7

This also happens on 5.7.

I've created an issue and a resolution here:

https://bugreports.qt.io/browse/QTBUG-55077

TL;DR = Add the location of the LIBPQ.DLL client library to your windows PATH envar.