QAbstractItemModel memory usage - c++

Question

I'm reading a ~2 MB json file to a QAbstractItemModel visualised by a QTreeView. Each json object converts to a row in the model. The program consumes +700 MB in memory. This ratio of storage space and memory usage is not very satisfying.
I assume, the QAbstractItemModel is responsible:
Using a very small json file, memory consumption drops to ~50 MB.
Disabling the views setModel function does not change the memory consumption significantly.
Is this the behavior to be expected? I assume not.
Is there a way to optimise the memory usage? I assume this should be handled in the models data item realisation. I attached my RowItem realisation in the following:
.h file:
class RowItem
{
public:
explicit RowItem();
virtual ~RowItem();
void setParent( RowItem * p_pParent );
void appendChild( RowItem * p_pChild );
void insertChild( int p_nRow, RowItem * p_pChild );
bool removeChild(int p_nRow);
bool replaceChild(RowItem * p_pOldChild , RowItem *p_pNewChild);
RowItem * child( int p_nRow ) const;
int rowCount() const;
int columnCount() const;
int column( const QVariant & p_grData, int p_nRole = Qt::DisplayRole ) const;
QVariant data(const int & p_nColumn, int p_nRole = Qt::DisplayRole ) const;
int row() const;
RowItem * parentItem();
bool setData( const int & p_nColumn, const QVariant & p_grData, int p_nRole = Qt::DisplayRole );
RowItem & operator=( RowItem & pSrc );
protected:
QList< RowItem * > m_pChildItems;
QList< QMap< quint8, QVariant > > m_grColList; /// #attention List index = column; value map: quint8 = p_nRole ( e.g. Qt::DisplayRole, limited to max 256), QVarinat = data
RowItem * m_pParentItem;
};
.cpp file
RowItem::RowItem() : m_pParentItem( nullptr )
{
}
RowItem::~RowItem()
{
qDeleteAll(m_pChildItems );
}
void RowItem::setParent(RowItem *p_pParent)
{
m_pParentItem = p_pParent;
}
void RowItem::appendChild(RowItem *p_pChild)
{
m_pChildItems.append(p_pChild);
p_pChild->setParent( this );
}
void RowItem::insertChild(int p_nRow, RowItem *p_pChild)
{
m_pChildItems.insert( p_nRow, p_pChild );
p_pChild->setParent( this );
}
bool RowItem::removeChild(int p_nRow )
{
if ( m_pChildItems.size() <= p_nRow ) {
return false;
}
RowItem * pChild = m_pChildItems.at( p_nRow );
delete pChild;
pChild = nullptr;
m_pChildItems.removeAt( p_nRow );
return true;
}
bool RowItem::replaceChild(RowItem * p_pOldChild, RowItem * p_pNewChild )
{
if ( ( p_pOldChild == nullptr ) || ( p_pNewChild == nullptr ) ) {
return false;
}
int nIdx = m_pChildItems.indexOf( p_pOldChild );
if ( nIdx == -1 ) {
return false;
}
m_pChildItems.replace( nIdx, p_pNewChild );
p_pNewChild->setParent( this );
return true;
}
RowItem *RowItem::child(int p_nRow) const
{
if ( ( p_nRow >= m_pChildItems.size() ) || ( p_nRow < 0 ) )
{
QLOG_ERROR() << "Requested child item not existent. m_pChildItems.size() = " << m_pChildItems.size() << "; requested item:" << p_nRow << Q_FUNC_INFO;
return nullptr;
}
return m_pChildItems.at(p_nRow);
}
int RowItem::rowCount() const
{
return m_pChildItems.count();
}
int RowItem::columnCount() const
{
return m_grColList.count();
}
int RowItem::column(const QVariant &p_grData, int /*p_nRole*/) const
{
for( int i = 0; i < m_grColList.size(); ++i ) {
const QMap< quint8, QVariant > & grRoleMap = m_grColList.at( i );
if( grRoleMap.values().contains( p_grData ) == true ) {
return i;
}
}
return -1;
}
QVariant RowItem::data(const int &p_nColumn, int p_nRole) const
{
if ( ( p_nColumn < 0 ) || ( p_nRole < 0 ) ) {
QLOG_ERROR() << "Requested invalid column or role data:" << p_nColumn << p_nRole << Q_FUNC_INFO;
return QVariant();
}
if ( m_grColList.size() <= p_nColumn ) {
QLOG_ERROR() << "Requested column does not exists. Column size is " << m_grColList.size() << "; requested was col" << p_nColumn << Q_FUNC_INFO;
return QVariant();
}
const QMap< quint8, QVariant > & grRoleMap = m_grColList.at( p_nColumn );
QVariant grValue = grRoleMap.value( p_nRole, QVariant() );
if ( ( p_nRole == Qt::EditRole ) && ( ! grValue.isValid() ) ) {
grValue = grRoleMap.value( Qt::DisplayRole, QVariant() );
}
return grValue;
}
int RowItem::row() const
{
int nRow = 0;
if ( m_pParentItem != nullptr ) {
nRow = m_pParentItem->m_pChildItems.indexOf( const_cast< RowItem* >( this ) );
}
return nRow;
}
RowItem *RowItem::parentItem()
{
return m_pParentItem;
}
bool RowItem::setData( const int & p_nColumn, const QVariant &p_grData , int p_nRole)
{
QMap< quint8 , QVariant > grRoleMap;
int nCol = p_nColumn;
if ( p_nColumn == -1 ) {
m_grColList.append( QMap< quint8 , QVariant >() );
nCol = m_grColList.size() - 1;
}
else {
// expand coloumns if required
while( m_grColList.size() <= p_nColumn ) {
m_grColList.append( QMap< quint8 , QVariant >() );
}
grRoleMap = m_grColList.at( p_nColumn );
}
grRoleMap.insert( p_nRole, p_grData );
m_grColList.replace( nCol, grRoleMap );
return true;
}
RowItem &RowItem::operator=(RowItem &p_grSrc)
{
m_grColList = p_grSrc.m_grColList;
return * this;
}