QSortFilterProxyModel is super slow in Qt-5.15.2

[Sivan]

Hi all,

I am currently using Qt-5.15.2 on MacOS 14.5 (MacBook Pro M1) and creating a feature that uses QSortFilterProxyModel. This feature is part of an existing complex application and upgrading to Qt 6 is not a choice at the moment. I noticed that whenever I tried to filter items, the process was extremely slow.

Here is my test case. I used customsortFilterModel example in Qt and simplified it.

• The original model is a simple model inherited from QAbstractItemModel.
• In this model, the rowCount is 25000 while columnCount is only 3.
• Removed the proxy view (QTreeView) from the example as it was very slow to even launch the app.
• Connected a button to do the filtering on proxyModel (QSortFilterProxyModel). In the slot of the button click, I called invalidateFilter() on the proxyModel.
• Override filterAcceptRow function to return true/false for even/odd rows respectively.

SourceModel::SourceModel(QObject* p_Parent)
    : QAbstractItemModel(p_Parent)
{
}

SourceModel::~SourceModel()
{
}

QVariant SourceModel::headerData(int p_Section, Qt::Orientation p_Orientation, int p_Role) const
{
    if (p_Role != Qt::DisplayRole) return QVariant();

    switch (p_Section)
    {
        case 1: return QVariant("Column 1");
        case 2: return QVariant("Column 2");
        default:
            return QVariant("Column 3");
    }
}

QVariant SourceModel::data(const QModelIndex& p_Index, int p_Role) const
{
    if (p_Role != Qt::DisplayRole) return QVariant();

    switch (p_Index.column())
    {
        case 1: return QVariant(p_Index.row() + 1);
        case 2: return QVariant(QString("Column 2 Row %1").arg(p_Index.row() + 1));
        default:
            return QVariant(QString("Last Column Row %1").arg(p_Index.row() + 1));
    }
}

int SourceModel::rowCount(const QModelIndex& p_Parent) const
{
    return 25000;
}

int SourceModel::columnCount(const QModelIndex& p_Parent) const
{
    return 3;
}

QModelIndex SourceModel::index(int p_Row, int p_Column, const QModelIndex& p_Parent) const
{
    return createIndex(p_Row, p_Column);
}

MySortFilterProxyModel::MySortFilterProxyModel(QObject *parent)
    : QSortFilterProxyModel(parent)
{
}

void MySortFilterProxyModel::SetIsFilterRows(bool p_IsFilter)
{
    isFilter = p_IsFilter;
    invalidateRowsFilter(); // invalidateFilter();
}

bool MySortFilterProxyModel::filterAcceptsRow(int sourceRow,
        const QModelIndex &sourceParent) const
{
    if (!isFilter) return true;

    return (sourceRow & 1);
}

Window::Window()
{
     proxyModel = new MySortFilterProxyModel(this);
     sourceView = new QTreeView;

    .... // Other UI inits

    QPushButton* btn = new QPushButton("Filter Items", this);
    btn->setCheckable(true);
    connect(btn, &QPushButton::toggled, proxyModel, &MySortFilterProxyModel::SetIsFilterRows);

    ... // Add to layouts
}

void Window::setSourceModel(QAbstractItemModel *model)
{
    proxyModel->setSourceModel(model);
    sourceView->setModel(model);
}

void Window::showEvent(QShowEvent* p_Event)
{
    const QModelIndex& index = proxyModel->mapToSource(proxyModel->index(0, 0)); // To force the proxy model to create mapping since there is no proxy view now. 
    QWidget::showEvent(p_Event);
}

Observations - Whenever the model is filtering data, it's extremely slow. It takes about 5 seconds plus. It is not even because of the view since I removed the proxy view. I have attached screenshot from time profile

I backported the following fixes, and used invalidateRowsFilter() instead
https://github.com/qt/qtbase/commit/8455bfee76ed3f1bd3bba8bd3688a7afa94ae0bb
https://github.com/qt/qtbase/commit/b5f6a85d274

It improved the performance from 5 seconds to 3 seconds plus. But I still find it slow. Finally, I tried it with Qt6. And that improved the performance tremendously (~200ms). However, I am not able to find any other commits that would contribute to this performance improvement. I am suspecting the replacement of QVector to QList, but I am not sure.

Could any expert here please advise on what contributes to the performance improvement in Qt6. Thanks in advance.

[SGaist]

Hi,

I see a lot of call to detach which seems odd for just showing data.
Can you share your model implementation ?

[Sivan]

Hi @SGaist , both the source and proxy model code are attached above. I just did not include header files.

[Sivan]

I was able to fix this with the following:
https://github.com/qt/qtbase/commit/7d92ef63d7c

And the following patch in Qt-5.15.2 which tremendously improved the timing: