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I am developing an application using QtRuby and PostgreSQL. I successfully developed and running successfully in Linux. Now i want to run the same application in windows. But I am failing to connect to database(postgresql). I am getting the following errors:

 QSqlDatabase: QPSQL driver not loaded
 QSqlDatabase: available drivers: QSQLITE QODBC3 QODBC
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As the error message says, the QPSQL driver is not available for Qt to talk to Postgres with. Probably the plugin has not been compiled yet.

As this how-to indicates, you need to install the PostgreSQL developer libraries, and then manually build the Qt driver plugin. See the how-to for the exact commands.

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Thanks for your reply. I compiled driver and it generated qsqlpsql4.dll, but still i am getting the same error. What should i do now.
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  1. Compile the QPSQL plugin as instructed here: http://ldc.usb.ve/docs/qt/sql-driver.html#qpsql-for-postgresql-version-7-3-and-above
  2. Add the PostgreSQL bin path to your PATH environment variable
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Postgresql using QT in Windows: How to compile driver QPSQL - MinGw - Win7

1) check installation directory, in my pc:

PostgreSQL (32 bit)    C:\PSQL32\bin
Qt (32 bit)            C:\QT\4.8.0\bin
MingW32                C:\QT\qtcreator-2.4.0\mingw\bin

2) add these 3 directory to system PATH

3) Download 'mingw-utils' and install in C:\Qt\4.8.0\bin (need utility REIMP.exe)

4) Convert libpq.lib in useful format for mingw32:

CD C:\PSQL32\lib

REIMP -d libpq.lib

Open libpq.def and delete ALL "_" at the beginning of definitions

dlltool --input-def libpq.def --output-lib libpq.a --dllname libpq.dll

5) Compile:

CD C:\Qt\4.8.0\src\plugins\sqldrivers\psql

qmake -o Makefile "INCLUDEPATH+=C:\PSQL32\include" "LIBS+=C:\PSQL32\lib\libpq.a" psql.pro

mingw32-make debug

mingw32-make release

10) copy dll:

libqsqlpsqld4.a   qsqlpsqld4.dll    (debug)  

libqsqlpsql4.a   qsqlpsql4.dll      (release)

in the directory:

C:\Qt\4.8.0\plugins\sqldrivers

NEW problem for QT version 5.01

there is a multiple definitions of struct timespec

in file pthread.h of PostgreSQL (C:\PSQL32\include\pthread.h)

replace:

#ifndef HAVE_STRUCT_TIMESPEC

with:

#if ((!defined(_TIMESPEC_DEFINED)) && (!defined(HAVE_STRUCT_TIMESPEC)))

Done :-)

Faust

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Hello, I know it's been a while since this was post. But i am trying to make this work with no success. In my case it doesn't load the driver, but lists it as available. Also, I do not have the code for compiling the plugins. I installed the QT Opensource, tried to alter it and download the codes, but the plugins codes are not provided through the installer. What should I do?
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Great! It's done! However there are some tips to pay attention: 1. Mingw-utils, 0.4-1 will not work on Windows 7, we must use 0.3. 2. There is a psql.json file in the directory of PSQL driver, please don't delete it.

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