Method find

src/expr/src/relation/canonicalize.rs:522–538

(&'a mut self, x: &T)

impl<T: Clone + Ord> UnionFind<T> for BTreeMap<T, T> {
    fn find<'a>(&'a mut self, x: &T) -> Option<&'a T> {
        if !self.contains_key(x) {
            None
        } else {
            if self[x] != self[&self[x]] {
                // Path halving
                let mut y = self[x].clone();
                while y != self[&y] {
                    let grandparent = self[&self[&y]].clone();
                    *self.get_mut(&y).unwrap() = grandparent;
                    y.clone_from(&self[&y]);
                }
                *self.get_mut(x).unwrap() = y;
            }
            Some(&self[x])
        }
    }

    fn union(&mut self, x: &T, y: &T) {
        match (self.find(x).is_some(), self.find(y).is_some()) {