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Too much query executed with QSqlQuery cause fatal signal if executed in different thread

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  • C Offline
    C Offline
    cmra
    wrote on last edited by
    #12

    The processEvents() calls does not change nothing (I call it at line number 300 and the error happen at line 315 in release build). The error happen again.
    connName is a global QString variable defined in the QRunnableDerivedObject and it's value is "async_conn", but this connection name is used only with one QSqlDatabase at start of importing process, no more.

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

      So there's your problem: you are creating connections with the exact same name in all of your threads. You should make the name unique per thread. For example add the thread id to the connection string.

      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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      • C Offline
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        cmra
        wrote on last edited by
        #14

        No it doesn't...because as I explained before I have just one thread and so just one connection.. I create only one thread fot importing data and no other. The connections in the main app don't use thread to exec query and they have different names.
        I don't beleave that QThreadPool create more than one thread itself.

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        • C Offline
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          cmra
          wrote on last edited by
          #15

          I'm developing for and running the app on an Android Device.

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          • SGaistS SGaist

            So there's your problem: you are creating connections with the exact same name in all of your threads. You should make the name unique per thread. For example add the thread id to the connection string.

            C Offline
            C Offline
            cmra
            wrote on last edited by
            #16

            @SGaist I tried also to add to the connName variable the thread Id by QThread::currentThreadId() so the new name is (for example): async_connca6b1920 but this don't solve my problem.

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            • C Offline
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              cmra
              wrote on last edited by
              #17

              I tried also to re install qt - android sdk and ndk- changing testing phone...but nothing of these solutions solve the problem...

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #18

                To be sure to understand you correctly, you are trying to execute 33000 queries on an Android phone ? What kind of device is that ?

                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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                • C Offline
                  C Offline
                  cmra
                  wrote on last edited by cmra
                  #19

                  Yes it is right....I tried on Samsung S6 and Samsung j6. But I already execute with success all the queries in the past, but now I can't find what wrong...if depend by an update of android sdk or ndk or I made a mistake in some place (the code is so simple that I exclude that).
                  So I ask for help to you because may be some errors that I can't see.

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                  • C Offline
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                    cmra
                    wrote on last edited by cmra
                    #20

                    And I think that the problem is not the high number of queries, because it fails after only 300... 300 is not too much.

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                    • C Offline
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                      cmra
                      wrote on last edited by
                      #21

                      ....and FINALLY I FOUND THE SOLUTIONS that wasn't in this part of code (this is correct)...
                      I use reference & to a global variable in the base app and assign it to a pointer * = &var.. When declare as pointer also the global variable all works good.
                      Thanks too much all people help me, but the problem was not here. I'm sorry to busy your time...
                      Thanks again.

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

                        Glad you found out !

                        Global variable ?

                        They should be avoided as much as possible. What is it and what are you doing with it ?

                        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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                        • C Offline
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                          cmra
                          wrote on last edited by cmra
                          #23

                          The global variables are custom classes to manage the tables of database derived by QObject class. I write inside them functions to read and write data and the tables structure.

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                          • C Offline
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                            cmra
                            wrote on last edited by
                            #24

                            The strange thing is that I don't use these variables in the new thread but I use only the QStringList passed.
                            But the error happen only in the new thread during the import otherwise the app seam to work right.
                            I don't know why.
                            To develop the app I use qml and I use "qmlRegisterType()" to use c++ object.

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #25

                              If you really need that kind of global object (which you likely don't), then you should rather implement them as singletons with proper access protection.

                              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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                              • C Offline
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                                cmra
                                wrote on last edited by
                                #26

                                It's ok...thanks again for your time!

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