SQLite and QTableView: Custom sorting is slow

[YuriQ]

Hello.

My primary goal is simple - to show SQLite table on QTableView. My secondary goal is to add ability for user to move rows up and down. I call it custom sorting. So this is why I use special 'position' column for sorting. So to move any row up I need just to swap it's position with row above it. And it works. But the thing is it works very slow even for very simple table like in the example below.

Question 1: Why is it so slow? Can it be faster?
Question 2: Can you suggest better/faster/different approarch for custom sorting?

Thanks in advance.

My environment: Windows 10 x64, Qt 5.10.1 msvc2015 32bit

UPD:
Maybe it is better to give up on SQLite and use QTableWidget, std::map, data structures and serialization instead. It is not so convenient compared to SQL database but at least it should work fast.

Sample code:

/*
File name: main.cpp

Project file:
QT       += core gui sql
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = MySqlTest
TEMPLATE = app
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \main.cpp
HEADERS +=
*/

#include <QApplication>
#include <QWidget>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QTableView>
#include <QHeaderView>
#include <QSqlTableModel>
#include <QSqlDatabase>
#include <QSqlQuery>

class MainWidget: public QWidget
{
    Q_OBJECT
public:
    MainWidget(QWidget* parent = Q_NULLPTR)
        : QWidget(parent)
    {
        // Setup database
        db = QSqlDatabase::addDatabase("QSQLITE");
        db.setDatabaseName("test.db");
        db.open();
        QSqlQuery query;
        query.exec("DROP TABLE items");
        query.exec(
                    "CREATE TABLE items ("
                        "id       INTEGER PRIMARY KEY UNIQUE NOT NULL,"
                        "position INTEGER NOT NULL,"
                        "name     VARCHAR NOT NULL DEFAULT ''"
                    ")"
                    );
        query.exec("INSERT INTO items ([position], name) VALUES (1, 'apple')");
        query.exec("INSERT INTO items ([position], name) VALUES (2, 'biscuit')");
        query.exec("INSERT INTO items ([position], name) VALUES (3, 'coconut')");
        query.exec("INSERT INTO items ([position], name) VALUES (4, 'donut')");
        query.exec("INSERT INTO items ([position], name) VALUES (5, 'egg')");
        query.exec("INSERT INTO items ([position], name) VALUES (6, 'fig')");
        query.exec("INSERT INTO items ([position], name) VALUES (7, 'garlic')");
        query.exec("INSERT INTO items ([position], name) VALUES (8, 'hamburger')");

        // Setup GUI
        setLayout(&layout);
        layout.addLayout(&layoutButtons);
        layoutButtons.addWidget(&buttonUp);
        buttonUp.setText("Move current up");
        connect(&buttonUp  , &QPushButton::clicked, this, &MainWidget::onMoveUp);
        connect(&buttonDown, &QPushButton::clicked, this, &MainWidget::onMoveDown);
        layoutButtons.addWidget(&buttonDown);
        buttonDown.setText("Move current down");
        layout.addWidget(&view);

        // Setup model and view
        model = new QSqlTableModel(this, db);
        model->setTable("items");
        model->setSort(1, Qt::AscendingOrder); // sort by position
        model->select();
        view.setModel(model);
        view.hideColumn(0); // hide id
        view.hideColumn(1); // hide position
        view.horizontalHeader()->hide();
        view.setSelectionMode(QAbstractItemView::SingleSelection);
        view.setSelectionBehavior(QAbstractItemView::SelectRows);
        model->setEditStrategy(QSqlTableModel::OnManualSubmit);
    }
    void onMoveUp()
    {
        int row = view.currentIndex().row();
        if (row > 0) // Can't move first row up
            swapRows(row, row-1);
    }
    void onMoveDown()
    {
        int row = view.currentIndex().row();
        if (row < model->rowCount()-1) // Can't move last row down
            swapRows(row, row+1);
    }
    void swapRows(int row1, int row2)
    {
        QModelIndex index1 = model->index(row1, 1);
        QModelIndex index2 = model->index(row2, 1);
        uint position1 = model->data(index1).toUInt();
        uint position2 = model->data(index2).toUInt();
        model->setData(index1, position2);
        model->setData(index2, position1);
        model->submitAll();
        view.setCurrentIndex(model->index(row2, 0));
    }
private:
    QSqlDatabase db;
    QVBoxLayout layout;
    QHBoxLayout layoutButtons;
    QPushButton buttonUp;
    QPushButton buttonDown;
    QTableView view;
    QSqlTableModel* model;
};

#include "main.moc"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWidget w;
    w.show();

    return a.exec();
}

[YuriQ]

I created custom model which works fast enough. It fetches and writes data using queries. Seems like working solution.