Method let_in

src/expr/src/relation.rs:1586–1607

Store `self` in a `Let` and pass the corresponding `Get` to `body`.

(self, id_gen: &mut IdGen, body: Body)

    /// Store `self` in a `Let` and pass the corresponding `Get` to `body`.
    pub fn let_in<Body, E>(self, id_gen: &mut IdGen, body: Body) -> Result<MirRelationExpr, E>
    where
        Body: FnOnce(&mut IdGen, MirRelationExpr) -> Result<MirRelationExpr, E>,
    {
        if let MirRelationExpr::Get { .. } = self {
            // already done
            body(id_gen, self)
        } else {
            let id = LocalId::new(id_gen.allocate_id());
            let get = MirRelationExpr::Get {
                id: Id::Local(id),
                typ: self.typ(),
                access_strategy: AccessStrategy::UnknownOrLocal,
            };
            let body = (body)(id_gen, get)?;
            Ok(MirRelationExpr::Let {
                id,
                value: Box::new(self),
                body: Box::new(body),
            })
        }
    }

    /// Return every row in `self` that does not have a matching row in the first columns of `keys_and_values`, using `default` to fill in the remaining columns
    /// (If `default` is a row of nulls, this is the 'outer' part of LEFT OUTER JOIN)