void DimexReportsProcessor::countRows(const QString &databaseName, std::function<void(void)> onStart, std::function<void(long long)> onDone)
{
    auto watcher = getWatcher();

    watchers_ << watcher;

    connect(watcher, &Watcher::finished, [this, watcher, databaseName, onDone]()
    {
        QVariantMap result = watcher->future().result();

        if (result["job"].toString().compare("count") == 0)
        {
            long long rowsCount = result["count"].toLongLong();

            onDone(rowsCount);
        }
        freeWatchers_ << watcher;
        watchers_.removeAll(watcher);
        watcher->disconnect();
    });

    onStart();

    watcher->setFuture(QtConcurrent::run([databaseName, this]() -> QVariantMap
    {
        QVariantMap   result;
        QString       query = loadQuery("totalrowsnumberquery");
        soci::session sql(soci::firebird, QString("service=%1 user=SYSDBA password=masterkey").arg(databaseName).toStdString());
        long long     count = 0;

        sql << query.toStdString(), soci::into(count);
        result["job"] = QString("count");
        result["count"] = count;

        return result;
    }));
}



.........


    connect(ui->openButton, &QPushButton::clicked, [this]
    {
        QString fileName = QFileDialog::getOpenFileName(this, trUtf8("Select database files"), "", trUtf8("Firebird database files (*.fdb)"));

        if (!fileName.isNull())
        {
            qDebug() << fileName;

            processor_->countRows(fileName, [this, fileName]
            {
                ui->exportButton->setEnabled(false);
......
            },
            [this, fileName](long long rowsCount)
            {
                ui->rowsCountLabel->setText(trUtf8("[Rows count: <b style='color:green'>%1</b>]").arg(rowsCount));
                openedDataBaseName_ = fileName;
                ui->exportButton->setEnabled(true);
            });
        }
        else
        {
.....

        }
    });