Method combine

datafusion/common/src/cse.rs:117–122

(mut self, other: Option<Self>)

    }

    fn combine(mut self, other: Option<Self>) -> Self {
        other.map_or(self, |other_id| {
            self.hash = combine_hashes(self.hash, other_id.hash);
            self
        })
    }
}

/// A cache that contains the postorder index and the identifier of [`TreeNode`]s by the