func (ng *Engine) cumulativeSubqueryOffset(path []Node) time.Duration {
	var subqOffset time.Duration
	for _, node := range path {
		switch n := node.(type) {
		case *SubqueryExpr:
			subqOffset += n.Range + n.Offset
		}
	}
	return subqOffset
}
func (ng *Engine) cumulativeSubqueryOffset(path []Node) time.Duration {
	var subqOffset time.Duration
	for _, node := range path {
		switch n := node.(type) {
		case *SubqueryExpr:
			subqOffset += n.Range + n.Offset
		}
	}
	return subqOffset
}
// cumulativeSubqueryOffset returns the sum of range and offset of all subqueries in the path.