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table.selectRow no doing anything

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  • P Offline
    P Offline
    PeterB74
    wrote on last edited by
    #6

    No longer stored qt_db as a class variable. Unloading code is changed to

        self.table.setModel(QtGui.QStandardItemModel())
        del self.card_model
        self.card_model = None
        QtSql.QSqlDatabase.removeDatabase(\
            QtSql.QSqlDatabase.database().connectionName())
    

    Does not help with the error message...

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #7

      Then please provide a minimal runnable code example that shows the issue.

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      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • P Offline
        P Offline
        PeterB74
        wrote on last edited by
        #8

        I've done some more debugging and it looks like the database stuff is a red herring. First of all, I have the same warnings on my machine, and they don't affect the row selection.

        Also, I now had the user execute the following code after the database has been unloaded and reloaded, and the model and the table have been completely reinitialised from scratch:

        def page_up_down_edit(self, up_down):
            <...database manipulation stuff...>
            self.table.selectRow(current_row + shift)
            QtWidgets.QMessageBox(text=f"Exit: selected_rows {current_row+shift} {self.table.selectionModel().selectedRows()}").exec_()
            return
        

        This shows a dialog on his machine displaying "Exit: selected_rows 435 []". So, no row gets selected, even though that's exactly what the previous command should do....

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #9

          Are you sure about the values of current_row and shift ?

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          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • P Offline
            P Offline
            PeterB74
            wrote on last edited by
            #10

            Yes, that's entirely expected.

            I am destroying and recreating the model and the table from scratch inbetween, though. Could it be related to that in any way? Or does the selectRow statement take a while to get into effect?

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #11

              Do you really need to destroy everything every time ?

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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              • P Offline
                P Offline
                PeterB74
                wrote on last edited by
                #12

                Yes, because I need to release access to the Qt database, so I have to invalidate the model.

                Meanwhile, I managed to get rid of a consistent 'qt_sql_default_connection' still in use' warning (I was still holding on to a variable containing the model), but that has had zero effect....

                self.table.selectRow(current_row + shift) does not do anything in that place in my code (at least on my user's machine), and no error message gets written to the console either.

                I tried all sorts of things, like rearranging my code, in the hope that I could work around this, but to no avail....

                My guess is that there's a very subtle bug in Qt that causes this, but as it only happens on some machines and in a quite specific scenario that cannot be be reduced to a simple runnable test case, it will be very difficult to track down what's happening.

                Unless people here have some brilliant insight or new things to try?

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #13

                  One thing you can do is to just clear the model content rather than replacing the whole model object.

                  What type of database are you using ?

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                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                  • P Offline
                    P Offline
                    PeterB74
                    wrote on last edited by PeterB74
                    #14

                    It's an sqlite database.

                    I do this when I unload the Qt view of the database:

                    self.table.setModel(QtGui.QStandardItemModel())
                    del self.card_model
                    self.card_model = None
                    

                    And when I reload, I do

                    self.card_model = CardModel(component_manager=self.component_manager)
                    self.card_model.setTable("cards")
                    <...>
                    self.table.setModel(self.card_model)
                    
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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #15

                      That looks pretty convoluted. Can you explain why you remove the connection ?

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                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                      • P Offline
                        P Offline
                        PeterB74
                        wrote on last edited by
                        #16

                        Because the backend library I use to process the necessary changes to the database is pure Python, so I need to release Qt's lock on the database first, have the Python library change the database, and then reload the database in Qt.

                        JonBJ 1 Reply Last reply
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                        • P PeterB74

                          Because the backend library I use to process the necessary changes to the database is pure Python, so I need to release Qt's lock on the database first, have the Python library change the database, and then reload the database in Qt.

                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by
                          #17

                          @PeterB74
                          I will say this then: if you are saying you are actually using non-Qt Python stuff to execute the database updates/access I wonder why you are also trying to use QSqlDatabase at all? Maybe you should go via the Python level model? Closing and re-opening the connection/database/model is an "expensive" operation. Just a thought, I admit I don't know your full situation.

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                          • P Offline
                            P Offline
                            PeterB74
                            wrote on last edited by
                            #18

                            I don't think replacing a fast C++ Qt direct database access with a slow Python wrapper is a good idea :-)

                            Updates to the database happen relatively infrequently, but scrolling through it and filtering is very common.

                            JonBJ 1 Reply Last reply
                            0
                            • P PeterB74

                              I don't think replacing a fast C++ Qt direct database access with a slow Python wrapper is a good idea :-)

                              Updates to the database happen relatively infrequently, but scrolling through it and filtering is very common.

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by
                              #19

                              @PeterB74
                              And you think the time taken to process the data in-memory in C++ versus in Python outweighs the time taken to access the data in the database across the library/protocol?

                              Anyway, best of luck.

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                              • P Offline
                                P Offline
                                PeterB74
                                wrote on last edited by
                                #20

                                The overhead of performing function calls in Python is very big because of the dynamical typing, and you need hundreds of calls to display a reasonable part of your table.

                                I tried it out, and scrolling becomes unbearingly slow... Accessing the database while staying in C is way more efficient than C calling Python which then calls C again.

                                JonBJ 1 Reply Last reply
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                                • P PeterB74

                                  The overhead of performing function calls in Python is very big because of the dynamical typing, and you need hundreds of calls to display a reasonable part of your table.

                                  I tried it out, and scrolling becomes unbearingly slow... Accessing the database while staying in C is way more efficient than C calling Python which then calls C again.

                                  JonBJ Offline
                                  JonBJ Offline
                                  JonB
                                  wrote on last edited by
                                  #21

                                  @PeterB74
                                  Point taken! I can only say I used Python/PyQt to do SQL database read/writes/attached as model for Qt views and found it fine for large data (obviously with suitable paging for views if required). But I wasn't doing any Python<->C++ (other, of course, than what's going on in Qt C++ code).

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                                  • SGaistS Offline
                                    SGaistS Offline
                                    SGaist
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #22

                                    One thing that intrigues me, why not just close the connection and reopen it after that ? It looks like there's no need to remove it completely. Or is the file trashed and recreated ?

                                    Interested in AI ? www.idiap.ch
                                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                    • P Offline
                                      P Offline
                                      PeterB74
                                      wrote on last edited by
                                      #23

                                      If I only close the connection but otherwise leave my table intact, I'm getting into trouble because it seems there are still paint calls to my delegates, which require Qt database access...

                                      But I guess I can add some logic to detect a closed database and return from the paint events without doing anything.

                                      I'll have my user try out a version where I do that, thanks for the suggestion!

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                                      • SGaistS Offline
                                        SGaistS Offline
                                        SGaist
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #24

                                        You can try QWidget's updatesEnabled property.

                                        Interested in AI ? www.idiap.ch
                                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                        • P Offline
                                          P Offline
                                          PeterB74
                                          wrote on last edited by
                                          #25

                                          My user got back to me, still the same behaviour. selectRow simply refuses to do anything...

                                          JonBJ 1 Reply Last reply
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