insert method
Implementation
void insert(dynamic key, int rowId) {
final r = root;
if (r.keys.length == 2 * order - 1) {
final s = BTreeNode(order: order, isLeaf: false);
s.children.add(r);
_splitChild(s, 0);
root = s;
_insertNonFull(s, key, rowId);
} else {
_insertNonFull(r, key, rowId);
}
}