PyQt4: Reading binary data from Postgresql fails under Windows

[leonidas]

I need to read from Postgresql bytea field that stores binary data and save to disk as pdf.
I use the following code, which it works under linux but fails under Windows.
@ self.db = QtSql.QSqlDatabase.database("my_connection")
if self.db.open():
query = QtSql.QSqlQuery(self.db)
query.exec_("SELECT Data FROM files where id =1")
query.next() # get first row
bytearr = query.value(0) # get the value of first field

        file=QTemporaryFile(QDir.tempPath() + "/XXXXXX." + '.pdf')

        file.setAutoRemove(False)
        file.open(QIODevice.WriteOnly)
        file.writeData(bytearr)

        QDesktopServices.openUrl(QUrl("file:///" + file.fileName()))# open pdf
        file.close()

@

The saved file looks corrupted when I run the code under Windows. There is no problem on Linux.
Could it be a PyQt version problem???

On Arch linux
@
('Qt version:', '4.8.6')
('SIP version:', '4.16.4')
('PyQt version:', '4.10.4-snapshot-f62fabcefe39')
@

On WINDOS 7
@('Qt version:', '4.7.1')
('SIP version:', '4.13.1')
('PyQt version:', '4.8.3')
@

[SGaist]

Hi and welcome to devnet,

It rather looks like your software doesn't find the PostgreSQL client libraries. Check with something like Dependency Walker

[leonidas]

I can connect to Postgresql and execute other queries but that one has a problem.

[SGaist]

Sorry, I've misunderstood your original problem. Saving a byte array in a file named something.pdf doesn't make it a valid pdf file. If you want to create a PDF you should create one using e.g. QPdfWriter

[leonidas]

Ok, the file can be any file format in the database i.e. zip, pdf,doc,jpg etc. Is there any generic way to exctract from database and write to disk?

[SGaist]

A text file works great

[leonidas]

Thank you. I 'll check it. I have already checked a pdf and an xml

[SGaist]

QFile doesn't know how to write pdf or xml just because you put that extension on the file name. It's your job to provide the right data.

[leonidas]

Is that an OS specific issue? It works under Linux and not under Windows?

[SGaist]

It's not OS nor Qt specific. A file extension doesn't do anything magic when writing programmatically to a file

[leonidas]

How is it explained that the code works under Linux?
With the same code I can write pdf and zip.
Thanks for your patience!