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<p>First and foremost using the PyQt database tools is completely
unnecessary and is either at the least adding much more complexity
than needed and at worst it is tying the front-end way to tightly
to the back-end which is just full numerous issues. However, on a
positive note you can interface with PostgresSQL and any other
database software using straight Python allowing one to build an
interface to the database that they can connect to the GUI via a
Data-Router (or Controller) thus in 90% or more of the cases where
you are dealing with a GUI and a data source (be it a database or
something else that supplies data) the MVC or (M-C/R-V)
methodology is generally the best method to apply as it keeps
things very simple and straight forward and you can later easily
add and/or change either the front-end and/or back-end without any
issues and these kind of changes do happen more often than one
might suspect. Next it also removes or at least reduces the
issues you might be having with drivers because once you get the
PostresSQL up and running you do not need anything more than the
Python library to interface with it.<br>
</p>
<div class="moz-cite-prefix">On 6/7/2020 12:02 PM, Nenad Lamza
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:dafb96fd-2540-f811-6e9e-bd524096e0ae@sk.t-com.hr">
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I use PostgreSQL 9.6.17 (installed on linux server on LAN) and
have Win10 (or Win7) clients with installed Python 3.7 or 3.8 and
PyQt 5.13.2, and my PyQt5 app that uses that PostgreSQL server
works ok, but I really don't know what I'm doing.<br>
<br>
I'll describe the problem. If I don't have PostgreSQL installed on
Win client (I don't need it because I use PostgreSQL on linux
server) or have installed it but not in path, my app crashes with
the error: "QSqlDatabase: QPSQL driver not loaded".<br>
<br>
So, I need some drivers. And I install PostgreSQL 9.6.x on Win
client and have it in path and after that everything works ok, but
only if I had luck and picked the right x in PostgreSQL 9.6.x
version.<br>
<br>
The alternative is that I don't install PostgreSQL 9.6.x (why
would I need to install it) on client machine and just copy some
dll files at the app directory. If I find the right files
(drivers), everything works ok, but if I don't, the app crashes
with the error: "QSqlDatabase: QPSQL driver not loaded" or worse,
recognize the PostgreSQL database on server, works ok some time,
but after the first, second or third query it crashes.<br>
<br>
Some driver combinations I copy to my app directory that work with
PyQt 5.13.2:<br>
<br>
1.<br>
Timestamp Size File<br>
25/02/2016 07:19 1,015,973 libiconv-2.dll<br>
07/01/2016 09:02 1,550,023 libintl-8.dll<br>
10/07/2019 20:20 145,408 libpq.dll<br>
<br>
2.<br>
Timestamp Size File<br>
21/06/2019 14:43 1,218,048 libeay32.dll<br>
25/02/2016 07:19 1,015,973 libiconv-2.dll<br>
07/01/2016 09:02 1,550,023 libintl-8.dll<br>
10/07/2019 20:20 145,408 libpq.dll<br>
21/06/2019 14:43 276,992 ssleay32.dll<br>
<br>
If I install PyQt 5.14 or 5.15 (instead of PyQt 5.13.2), the app
crashes, and I am afraid to upgrade PyQt5.<br>
<br>
So, my question is:<br>
How do I know which drivers I should copy to my app directory with
various version of PyQt5, that's the mistery to me. And also if
copying the drivers to my app directory is the right way at all?<br>
<br>
There's a fine answer here:<br>
<br>
<a class="moz-txt-link-freetext"
href="https://stackoverflow.com/questions/20884010/qt5-failed-to-load-psql-driver-in-windows"
moz-do-not-send="true">https://stackoverflow.com/questions/20884010/qt5-failed-to-load-psql-driver-in-windows</a><br>
<br>
"It's quite likely to be failing because there's a dependency of <code>qsqlpsql.dll</code>
missing - either <code>libpq.dll</code>, or one of the libraries
that <code>libpq</code> build requires." ... "<span
class="comment-copy">You should use the <i>same</i> libpq your
Qt's <code>qsqlpgsql.dll</code> was compiled against if
possible.</span>"<br>
<br>
If that's true, how should I know with what <span
class="comment-copy">libpq library qsqlpgsql.dll was compiled
in. I suppose </span>PyQt 5.13.2's <span class="comment-copy">qsqlpgsql.dll
is compiled with different version than </span><span
class="comment-copy">PyQt 5.14.x's <span class="comment-copy">qsqlpgsql.dll
or even </span></span><span class="comment-copy"><span
class="comment-copy">5.15.x's <span class="comment-copy">qsqlpgsql.dll</span></span>.<br>
<br>
Also, this link has some clues:<br>
<a class="moz-txt-link-freetext"
href="https://stackoverflow.com/questions/26507353/qpsql-driver-not-loaded-qt"
moz-do-not-send="true">https://stackoverflow.com/questions/26507353/qpsql-driver-not-loaded-qt</a><br>
<br>
And generally, what's the best way to work with </span><span
class="comment-copy">PostgreSQL in PyQt5. It obviously doesn't
work out of the box if </span><span class="comment-copy"></span><span
class="comment-copy">PostgreSQL is not installed on client
machine, and even if the wrong version is installed.<br>
<br>
</span>Nenad<br>
<br>
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