Qt Threads and the default QSQLDatabase connection (sqlite)

Question

Is it safe to use default database connection from different threads? Like this:

bool upSafe(const QString &mig_to, const QString &mig_from) const {
  if (!QSqlDatabase::database().transaction()) {
    qCCritical(hfCoreMT) << "Failed init database transaction";
    return false;
  }

  if (!up(mig_to, mig_from)) {
    QSqlDatabase::database().rollback();
    return false;
  }

  return QSqlDatabase::database().commit();
}

In function up default QSQLQuery created and executed. Maybe some hints to the right pattern?

read this: code.qt.io/cgit/qt/qtbase.git/tree/dist/changes-5.11.0/… — eyllanesc
– eyllanesc, Commented May 30, 2018 at 6:25
@eyllanesc should I interpret is as: "It should be safe but till 5.11 there was a bug" ? — ephemerr
– ephemerr, Commented May 30, 2018 at 6:29

peppe · Accepted Answer · 2018-05-30 07:07:44Z

2

QSqlDatabase (which represents one DB connection) is not reentrant. You can use a connection only from the thread you created it. If you need to perform queries from another thread you need to create another connection from that thread first.

answered May 30, 2018 at 7:07

peppe

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1 Comment

ephemerr Over a year ago

So the answer is "No". Default connection as any connectoin should be used only in thread where it have been opened.

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