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Tremendous Speed-Up with SQL Transactions

The function CustomerDatabase::importCustomers reads 500 customers from the list c_customers, creates an SQL query cmd for each customer and inserts each customer into the Customers table of the SQL database db.

void CustomerDatabase::importCustomers() {
    auto db = QSqlDatabase::database("CustomerDB");
    for (auto row : c_customers) {
        auto cmd = QString{"INSERT INTO Customers "
                   "(fullName, street, postalCode, city, phone, email) "
                   "VALUES (\'%1\')"}.arg(row.join("\', \'"));
        auto query = QSqlQuery{cmd, db};

On an NXP i.MX6 SoC with four Cortex-A9 cores, this function takes 17.5 seconds! Your user would have to wait more than 17.5 seconds for the import of a CSV file with 500 customers to finish. This is unacceptable. How can you speed up the import to 0.2 seconds?
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Performance Gains Through C++11 Move Semantics

We explore when and how our code benefits most from equipping classes with move constructors and assignment operators. We analyse in detail, which constructors and assignment operators (move or copy) are called for C++98 and C++11 when we insert or emplace objects into containers, when we initialise containers and when we shuffle and sort containers. Finally, we run benchmarks for these operations and discuss the actual speed-up, which ranges from 1% to 70%.
Read More »Performance Gains Through C++11 Move Semantics