QAbstractItemModel::endInsertRows message in terminal

[user4592357]

i have implemented incremental loading for tree view. when a new batch is being fetched, i get the following message in terminal, and the rest of node children do not load:
QAbstractItemModel::endInsertRows: Invalid index ( 123 , 0 ) in model QAbstractItemModel(0xwhatever)
here are relevant functions from tree model:

bool TreeModel::canFetchMore(const QModelIndex &parent) const
{
	if (!parent.isValid())
	{
		// return whether mode data is available
		return m_pRootNode->childCount() < m_pRootNode->actualChildCount();
	}

	// get the node pointer
	auto node = static_cast<TreeNode *>(parent.internalPointer());
	return node->childCount() < node->actualChildCount();
}

void TreeModel::fetchMore(const QModelIndex &parentIdx)
{
	// get the node pointer
	auto node = !parentIdx.isValid()
		? m_pRootNode.get()
		: static_cast<TreeNode *>(parentIdx.internalPointer());
	if (!node) return;

	// get the number of items to fetch
	const auto nChildCount = node->childCount();
	int itemsToFetch = qMin(node->childBatchCount(), node->actualChildCount() - nChildCount);
	if (itemsToFetch <= 0) return;

	// fetch the data from the node
	beginInsertRows(parent(parentIdx), nChildCount, nChildCount + itemsToFetch - 1);
	node->fetchItems(itemsToFetch);
	endInsertRows();
}

bool TreeModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
	if (!index.isValid())
		return false;

	// get the node pointer
	auto node = static_cast<TreeNode *>(index.internalPointer());

	bool bUpdated = true;
	if (role == Qt::DisplayRole)
	{
		QList<QVariant> data;
		data << value;
		node->setColumnsData(data);
	}
	else if (role == Qt::CheckStateRole)
	{
		bUpdated = node->setProperty(index.column(), value);
	}
	else
		bUpdated = false;

	// emit the dataChanged() signal
	if (bUpdated)
	{
		auto parentIndex = parent(index);
		auto topLeftIndex = this->index(0, 0, parentIndex);
		auto bottomRightIndex = this->index(
			rowCount(parentIndex) - 1, columnCount(parentIndex) - 1, parentIndex);
		emit dataChanged(topLeftIndex, bottomRightIndex);
	}

	return bUpdated;
}

void TreeModel::insertChild(TreeNode *parent, TreeNode *child, int row /* = -1 */)
{
	// get the parent node's model index
	auto parentIndex = index(parent);

	// adjust row if necessary
	if (row == -1)
		row = parent->childCount();

	// let the model know we're making modifications
	beginInsertRows(parentIndex, row, row);
	parent->addChild(child, row);
	endInsertRows();

	// update the model
	updateModel();
}

and from node:

void TreeNode::fetchItems(int itemsToFetch)
{
	QSqlQuery sqlQuery(QSqlDatabase::database(getPath()));
	sqlQuery.prepare(sQueryString).arg(itemsToFetch/* limit */).arg(childCount()/* offset */));

	sqlQuery.bindValue(key, value);
	if (!sqlQuery.exec()) return;

	while (sqlQuery.next())
	{
		// create a node
		addChild(new ChildNode(sqlQuery.value(0).toString(), this));
	}
}

the node is populated with only 60 items (20 is the batch fetch count), and the number of total items is 129, but the error reports 123.

[SGaist]

Hi,

Might be a silly question but are you sure that you are getting as much data as you think from the database ?

[user4592357]

i executed the query on the database and yes, i do get the 129 results.
i don't get why it's reporting 123, when i only have 60 child nodes currently

[Christian Ehrlicher]

Just add some debug output to see what really happens / how often the stuff is called.

[user4592357]

@Christian-Ehrlicher
i did. found out after inserting 60th child node from fetchMore, endInsertRows prints the message.

i looked at implementation of rowsInserted but i don't see how it could get from 60 to 123.

[user4592357]

EDIT: i found this issue, beginInsertRows should take parent index, not parent of parent.

i found more details on the issue.
so i have two level tree view:

a
|_a1
|_a2
|_...
b
|_b2

the problem occurs when i expand a first level node, e.g. a, and i get the message when the expanded node happens to be near the bottom.
when i moved the same node near top, there's no message in terminal.
so i guess the 123 i'm getting actually refers to first level item population, and not for expanded node.
but see, it says ( 123 , 0 ) i.e. first column, so why is it happening when i expand the node?
seems it is trying to insert expanded node's children as first level items, but first level items (rowCount()) are less than 123