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SQL connections on multiple threads in a Qt application

How can I create and use multiple SQL db connections on different threads in a Qt application?

I have read the documentation which says

The connection can only be used from the thread that created it.

How can I separate connections on different threads?

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3 answers


You need to create a database connection for each thread. Use QSqlDatabase::addDatabase()

with different named connections as parameters in each thread to instantiate QSqlDatabase

. A static function addDatabase

is thread safe and can be called on different threads.



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How can I create and use multiple sql db connections on different threads in a program using Qt?

// general worker init slot
DbWorker::init()
{
    this->db = QSqlDatabase::addDatabase("QSQLITE", dbName);
    db.setDatabaseName(dbPath);
    db.open();
}

when in your main class or wherever you are:



DbWorker w1 = new DbWorker;
w1.setDbName("mem_db");
w1.setDbPath(":memory:");
QThread* t1 = new QThread(this);
w1->moveToThread(t1);
connect(t1, SIGNAL(started()), w1, SLOT(init()));
t1->start();

DbWorker w2 = new DbWorker;
w1.setDbName("file_db");
w1.setDbPath("~/usr/foo.db");
QThread* t2 = new QThread(this);
w1->moveToThread(t1);
connect(t2, SIGNAL(started()), w2, SLOT(init()));
t1->start();

so you have a memory connection at thread1 and a file connection at thread2. the only thing to do is get the data into the gui stream if it is a gui app

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Follow this VoidRealms @youtube tutorial. It has a very good explanation on sql hookups, models and many other things about Qt.

If you still need more help after browsing, I'd love to send you a sample code to test.

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