QMYSQL SIGSEGV

[ckvsoft]

@JonB
This was a test while without these Options i got a "Lost connection to MySQL server during query" without SEGV but the Query was not made. The Server is running normaly without troubles Its a TCP connection while not on the same machine. I test an other Server with do the same. Tomorow i will test a localhost machine.

Its not allways the same query and not allways the prepare. Sometimes it is by "QSqlQuery query(dbc)" and somtime by the exec.

[SGaist]

What is that qrkcore library you are using ?

[ckvsoft]

@SGaist
This is a Part of my Application . Why?

[SGaist]

Well... To know whether it's an external library you are using or something you are implementing.

Do you have the same crash if you implement just a minimal application that connects to the database and does the queries ?

[ckvsoft]

@SGaist
I will try this at weekend. Also i will test if MySQL and MariaDB has the same. The queries where made from the library. Thx for the time

[ckvsoft]

Hi
I connect to a localhost mysql server and it seems to work. When i has running in the background some sql queries and i do at the same time from other window with the same connection any query it works.

When i connect to a server via TCP it will crash.
Edit: Its also with localhost, but the time is a bit longer ;(

[SGaist]

Can you trigger also that when using an application that's not using the QSql** classes ?

[ckvsoft]

I think i have found a solution ;-) Some Test will be good. I will enhance my tests.
The Idea i found by reading http://doc.qt.io/qt-5/threads-modules.html

Just my Application worked since 2015 with QSQLITE without troubles. But some users will also use MySQL.

For the solution i have adapted a database manager for my requirement.

[SGaist]

So you're using multiple threads to write to your database ?

[ckvsoft]

@SGaist
Yes. I Import JSON Files with an Import Walter Thread. Wenn a File is copied in a Directory it will Import and created new sql entries.
Nur Why SQlite has no Troubles?
I will also Move long Working Stuff to thread

Ob they GUI you also can do some queries by clicking Buttons

[SGaist]

I'd say pure luck.

Are you creating one connection per thread like suggested in the documentation ?

[ckvsoft]

@SGaist
Yes. The DatabaseManager save the connections per thread into a

QHash<QThread*, QHash<QString, QSqlDatabase> > 

I have only one thread at a time wich write to the database. All others max. 4 to only select
Sorry for my "Austrian English" ;-)

[SGaist]

Can you show how your are setting up the connections ?

[ckvsoft]

@SGaist

The first connection is in my first post
Than for every connection i call

QSqlDatabase dbc = DatabaseManager::database("CN");
QSqlQuery query(dbc)
.
.

.

#include "databasemanager.h"

#include <QSqlDatabase>
#include <QMutexLocker>
#include <QThread>
#include <QSqlError>
#include <QDebug>

QMutex DatabaseManager::s_databaseMutex;
QHash<QThread*, QHash<QString, QSqlDatabase> > DatabaseManager::s_instances;

QSqlDatabase DatabaseManager::database(const QString& connectionName)
{
    QMutexLocker locker(&s_databaseMutex);
    QThread *thread = QThread::currentThread();

    // if we have a connection for this thread, return it
    QHash<QThread*, QHash<QString, QSqlDatabase> >::Iterator it_thread = s_instances.find(thread);
    if (it_thread != s_instances.end()) {
        QHash<QString, QSqlDatabase>::iterator it_conn = it_thread.value().find(connectionName);
        if (it_conn != it_thread.value().end()) {
            QSqlDatabase connection = it_conn.value();
//            qDebug() << "Function Name: " << Q_FUNC_INFO << " found SQL connection instances Thread: " << thread->currentThreadId() << " Name: " << connectionName;
            if (connection.isValid())
                return it_conn.value();
        }
    }

    // otherwise, create a new connection for this thread
    QSqlDatabase connection = QSqlDatabase::cloneDatabase(
                                  QSqlDatabase::database(connectionName),
                                  QString("%1_%2").arg(connectionName).arg((int)thread));

    // open the database connection
    // initialize the database connection
    if (!connection.open()) {
        // Todo: Exeption Handling
        qCritical() << "Function Name: " << Q_FUNC_INFO << connection.lastError().text();
        return connection;
    }

    qDebug() << "Function Name: " << Q_FUNC_INFO << " new SQL connection instances Thread: " << thread->currentThreadId() << " Name: " << connectionName;

    s_instances[thread][connectionName] = connection;
    return connection;
}

#ifndef DATABASEMANAGER_H
#define DATABASEMANAGER_H

#include "qrkcore_global.h"

#include <QMutex>
#include <QHash>
#include <QSqlDatabase>

class QThread;

class QRK_EXPORT DatabaseManager
{
    public:
        static QSqlDatabase database(const QString& connectionName = QLatin1String(QSqlDatabase::defaultConnection));
    private:
        static QMutex s_databaseMutex;
        static QHash<QThread*, QHash<QString, QSqlDatabase>> s_instances;

};

#endif // DATABASEMANAGER_H

I found the code and adapted it for my requirement.

[ckvsoft]

So. I made some tests with create more than 1000 receipts and do concurrent imports with 10000 Products and do some select. I seems it works now without any troubles localhost and IP also over slow connection over the internet.

i think it fix my problem.
lg chris