Method is_valid

datafusion/optimizer/src/common_subexpr_eliminate.rs:701–704

(node: &Expr)

    }

    fn is_valid(node: &Expr) -> bool {
        !node.is_volatile_node()
            && !matches!(node, Expr::Lambda(_) | Expr::LambdaVariable(_))
    }

    fn is_ignored(&self, node: &Expr) -> bool {
        // MoveTowardsLeafNodes expressions (e.g. get_field) are cheap struct