[workaround] qt_sql_default_connection' is still in use --- again
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Hi
I'm developing a small daemon, which at regular intervals (many times every hour) opens a database connection, inserts some records, and closes the connection again.
Everything works great, except every time the database connection is closed, I get the very well known "qt_sql_default_connection' is still in use" message, some small memory leak and an open connection to the database (after some time I get "Too many connections QMYSQL:").
The funny thing is : I do not have to use any query to get the error, all I have to do, is to connect to the database, and disconnect again!
I have made this small test program, which also displays the error.
I have a form with two buttons, one for connect, one for disconnect.
@#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QSqlDatabase>MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}MainWindow::~MainWindow()
{
delete ui;
}void MainWindow::on_pushButton_clicked() // connect
{
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("localhost");
db.setDatabaseName("test");
db.setUserName("user");
db.setPassword("pwd");
db.open();
}void MainWindow::on_pushButton_2_clicked() // disconnect
{
QSqlDatabase::database().close();
QSqlDatabase::removeDatabase(QSqlDatabase::database().connectionName());
}
@Any ideas ?
I'm using QtCreator 5.1 and mysql 5.5.32 on Ubuntu 64 bit.
Kim
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Hi,
Just a design question, why not setup the database once and only open and close it ?
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Hi SGaist
That solution has crossed my mind, but because of my in-experience with this kind of long running processes (it could be running un interrupted for months), I decided this approch would be best.
What would you say is the better solution, one permanent connection, or a new one each time ?
Kim
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AFAIK, you can go with one database setup at application startup and open/close the connection has needed. Just be sure that all the transaction to the database have been executed before closing the connection.
