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