fast way to update 10M record in Mysql database using QT

Question

I have a 500MB file which contains a data that I need to use it to update a table that contains 10M rows so I use this code in using QT SQL library

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
// my database info 
db.transaction(); // start the transaction
    QSqlQuery q;
    QString sql = ""; // to append many sql statment to this string

    QFile file(dataFile);
    file.open(QIODevice::Text | QIODevice::ReadOnly);
    QTextStream stream(&file);

    int counter = 0;
    clock_t tStart = clock();
    while (!stream.atEnd()) {
        counter++;
        QString str = stream.readLine();
        QStringList list = str.split(';');
        QString id = list[0];
        QString streetName = list[1];
        QString HouseName = list[2];
        QString HouseNumber = list[3];
        QString city = list[4];
        QString postalCode = list[5];

        QString temp_sql = "UPDATE temp_table_copy SET street_name='!1', house_number='!2',postal_code='!3',address_city='!4', house='!5' where id=" + id + ";";
        temp_sql = temp_sql.replace("!1", streetName);
        temp_sql = temp_sql.replace("!2", HouseNumber);
        temp_sql = temp_sql.replace("!3", postalCode);
        temp_sql = temp_sql.replace("!4", city);
        temp_sql = temp_sql.replace("!5", HouseName);

        sql += temp_sql;
        if (sql.size() >= 100000) {
            if (!q.exec(sql)) {
                 qDebug() << "Excute Error: " << q.lastError().text();
            }
            sql = "";
            printf("Finished: %d sql statment\n", counter);
        }

        if (counter == Number)
            break;
    }
    if (!sql.isEmpty()) {
        if (!q.exec(sql)) {
            qDebug() << "Excute Error: " << q.lastError().text();
        }
        printf("Finished: %d sql statment\n", counter);
    }
    db.commit(); // commit and


    printf("Time taken: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
    db.close();

the idea is I append the big SQL string with the SQL statement and when it reaches the 100,000 in size I execute it and empty the string to avoid bad allocation when the string is too much size in memory, and also I read that MySQL database has a certain size to the SQL statement to be executed and I get its limit using

SHOW VARIABLES LIKE 'max_allowed_packet';

the problem here is that not all the data are updated some ids have a value in the text file and not updated inside the MySQL database table so what can be the problem? those columns are null before the update so when I try to count how many not update I found 7M only which means some ids are not updated and also I did not get any error from the query, any help or suggestion to know why this happened, or a better way to do it.
Thanks in advance.

Is the any really good cause, why you didnÄ't use prepared statements and opted for an unsecure text concatination? see https://doc.qt.io/qt-5/sql-sqlstatements.html — nbk, Apr 05 '20 at 11:37
when I try to execute one command at time using statements the 1000 only take 287 seconds, which will take days to make the 10M rows update, i read that to save time to minimize excutes and try to make it in one query. — user7179690, Apr 05 '20 at 11:52
Suggest making the file as SQL file instead of text. overhead at parsing text and execute query row by row. — JustWe, Apr 05 '20 at 13:10

fast way to update 10M record in Mysql database using QT

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