if (!system(sh.str().c_str())) {
    // 4.3) execute shared library code
    void* handle = dlopen("../shared/lib.so", RTLD_NOW | RTLD_GLOBAL);
    if (!handle) {
        cerr << "error: " << dlerror() << endl;
        exit(1);
    }
    auto fn = reinterpret_cast<void (*)(
                    Database *)>(dlsym(handle, "run"));
    std::cout << fn << std::endl;
    if (!fn) {
        cerr << "error: " << dlerror() << endl;
        exit(1);
    }
    std::cout << "[ ] execute query" << std::endl;
    fn(db); // execute query

    // 4.4 print measurement results
    dlclose(handle);
}