Querying within Threads

[jacek]

qplot is an object of the ui file which is a plotting application.
In the above code there are lineEdits for from and to dateTime which are entered by the user and accessed here.

Then read this carefully: http://doc.trolltech.com/3.3/threads.html
Especially the part about classes that use implicit sharing (like QString) and about classes derived from QObject.

[pdoria]

Hey bera82

Remember that each connection to the DB must be uniquely named ...

I use the following when working with dbconns inside threads:

// create a unique database connection to serve this thread
// two calls to rand() are a bit expensive but *effective*...
// note: this is for a PostgreSQL connection ..
sprintf(dbUnique, "myDB%x%x", rand(), rand() );
myDB = QSqlDatabase::addDatabase ( "QPSQL", dbUnique );
// set needed conn parameters here...
 
// whatever code...
QSqlQuery query(myDB);		// this is the important part: access it by its unique name.
 
// remember to close after you're done... (or upon the thread's destruction)
myDB.close();

// create a unique database connection to serve this thread
// two calls to rand() are a bit expensive but *effective*...
// note: this is for a PostgreSQL connection ..
sprintf(dbUnique, "myDB%x%x", rand(), rand() );
myDB = QSqlDatabase::addDatabase ( "QPSQL", dbUnique );
// set needed conn parameters here...

// whatever code...
QSqlQuery query(myDB);		// this is the important part: access it by its unique name.

// remember to close after you're done... (or upon the thread's destruction)
myDB.close();

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HTH,
Pedro Doria Meunier