QSqlDatabasePrivate::removeDatabase: connection 'cbsdb' is still in use.

rahulvishwakarma

hi to all, I am building a small project. I've centos 6.10 server of mysql, and centos 7.5 as client of Qt 5.7.
here i created login form( DialogLogin ),
here is mine dialoglogin.h:-

#ifndef DIALOGLOGIN_H
#define DIALOGLOGIN_H

#include <QDialog>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QMessageBox>
#include <QString>
#include <QSqlError>

#include "dialogmenu.h"

class DialogMenu;

namespace Ui {
class DialogLogin;
}

class DialogLogin : public QDialog
{
    Q_OBJECT

public:
    explicit DialogLogin(QWidget *parent = 0);
    ~DialogLogin();

    QSqlDatabase *db;

private slots:


    void on_pushButtonCancel_clicked();

    void on_pushButtonLogin_clicked();

private:
    Ui::DialogLogin *ui;
//    QSqlDatabase *db;
    QString sql;
    QSqlQuery *query;

    DialogMenu *dlgmenu;
};

#endif // DIALOGLOGIN_H

and dialoglogin.cpp :-

#include "dialoglogin.h"
#include "ui_dialoglogin.h"

DialogLogin::DialogLogin(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::DialogLogin)
{
    ui->setupUi(this);
    QString database = "cbsdb";
    db = new QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL", "cbsdb"));
    db->setDatabaseName("cbs");
    db->setHostName("serverora.db.net");
    db->setUserName("rahul");
    db->setPassword("rahul");
    db->setPort(3306);

    dlgmenu = new DialogMenu(this);
    query = new QSqlQuery;
}

DialogLogin::~DialogLogin()
{

    db->removeDatabase("cbsdb");
    db->close();
    delete db;
    delete ui;
}

void DialogLogin::on_pushButtonCancel_clicked()
{

    exit(0);
}

void DialogLogin::on_pushButtonLogin_clicked()
{
    if(db->open())
    {
        QMessageBox::information(this, "inside DialogLogin::db->open ","inside db->open");
        sql = "select User from tableLogin where User = ? and Password = ?";

//        query = new QSqlQuery(sql);

        QString user = ui->lineEditUserName->text().trimmed();
        QString password = ui->lineEditPassword->text().trimmed();
//        sql = "select user from tableLogin where User = '"+user +"' and Password = '"+password+"';";
        if(!query->prepare(sql))
        {
            QMessageBox::information(this, "inside DialogLogin::query->prepare", "Error : " + query->lastError().text());
            return;
        }

        query->bindValue(0, user);
        query->bindValue(1, password);

        if(query->exec())
        {
            if(query->next())
            {
                if(QString::compare(user, query->value(0).toString().trimmed()) == 0) // && ( QString::compare(password, query->value(1).toString().trimmed()) == 0) )
                {
                    //QMessageBox::information(this, "Login Form", "Login Correct");
                    this->close();
                    dlgmenu->exec();
                    db->close();
                }
                else
                {
                    QMessageBox::information(this, "Login Form", "user name or password is incorrect");
                }
            }
            else
            {
                QMessageBox::information(this, "Login Form", "query.next() is failed : " + query->lastError().text());
            }
        }
        else
        {
            QMessageBox::information(this, "Login Form", " Error in login " + query->lastError().text());
        }
    }
    else
    {
        QMessageBox::information(this,"cbs LoginForm", "database cannot be openned : " + db->lastError().text());
    }

    db->removeDatabase("cbsdb");
}

i added login->db->open() and login->db->close() in every function where i used database connection.e.g.

void DialogAddModifyMemberRecords::on_pushButtonDeleteRecord_clicked()
{
    if(login->db->open())
    {
        QString memstr = ui->lineEditMembershipNumber->text().trimmed();
        sql = "delete from tableMemberRecords where membershipno = '"+memstr+"'";
        qry->prepare(sql);
        if(qry->exec(sql) && !memstr.isEmpty())
        {
            QMessageBox::information(this, "deleting from member record", "record sucesfully deleted");
        }
        else
        {
            QMessageBox::critical(this, "deleting from member record", "Error " + qry->lastError().text());
        }
    }
    login->db->close();
}

now i am getting this error :-
QSqlDatabasePrivate::removeDatabase: connection 'cbsdb' is still in use, all queries will cease to work.
QSqlDatabasePrivate::addDatabase: duplicate connection name 'cbsdb', old connection removed.

how to get rid of this.

SGaist

Hi,

You are using QSqlDatabase wrongly.

Please read again the documentation of QSqlDatabase and especially the warning about not keeping a local copy of it.

Christian Ehrlicher

And apart from what @SGaist said, your order is wrong. First close the database, then remove the database connection

DialogLogin::~DialogLogin()
{
    QSqlDataBase::database("cdsdb").close();
    QSQLDataBase::removeDatabase("cbsdb");
    delete ui;
}