Method action

src/transform/src/fold_constants.rs:73–423

Replace operators on constants collections with constant collections. This transform will cease optimization if it encounters constant collections that are larger than `self.limit`, if that is set. It is not guaranteed that a constant input within the limit will be reduced to a `Constant` variant.

(
        &self,
        relation: &mut MirRelationExpr,
        relation_type: &mut ReprRelationType,
    )

    /// that are larger than `self.limit`, if that is set. It is not guaranteed that
    /// a constant input within the limit will be reduced to a `Constant` variant.
    pub fn action(
        &self,
        relation: &mut MirRelationExpr,
        relation_type: &mut ReprRelationType,
    ) -> Result<(), TransformError> {
        match relation {
            MirRelationExpr::Constant { .. } => { /* handled after match */ }
            MirRelationExpr::Get { .. } => {}
            MirRelationExpr::Let { .. } | MirRelationExpr::LetRec { .. } => {
                // Constant propagation through bindings is currently handled by in NormalizeLets.
                // Maybe we should move it / replicate it here (see database-issues#5346 for context)?
            }
            MirRelationExpr::Reduce {
                input,
                group_key,
                aggregates,
                monotonic: _,
                expected_group_size: _,
            } => {
                // Guard against evaluating an expression that may contain
                // unmaterializable functions.
                if group_key.iter().any(|e| e.contains_unmaterializable())
                    || aggregates
                        .iter()
                        .any(|a| a.expr.contains_unmaterializable())
                {
                    return Ok(());
                }

                if let Some((rows, ..)) = (**input).as_const() {
                    let new_rows = match rows {
                        Ok(rows) => {
                            if let Some(rows) =
                                Self::fold_reduce_constant(group_key, aggregates, rows, self.limit)
                            {
                                rows
                            } else {
                                return Ok(());
                            }
                        }
                        Err(e) => Err(e.clone()),
                    };
                    *relation = MirRelationExpr::Constant {
                        rows: new_rows,
                        typ: relation_type.clone(),
                    };
                }
            }
            MirRelationExpr::TopK {
                input,
                group_key,
                order_key,
                limit,
                offset,
                ..
            } => {
                // Only fold constants when:
                //