Struct mz_transform::normalize_lets::NormalizeLets

pub struct NormalizeLets {
    pub inline_mfp: bool,
}

Install replace certain Get operators with their Let value.

Fields

inline_mfp: bool

If true, inline MFPs around a Get.

We want this value to be true for the NormalizeLets call that comes right before crate::join_implementation::JoinImplementation runs because

• JoinImplementation cannot lift MFPs through a Let.
• JoinImplementation can’t extract FilterCharacteristics through a Let.

Generally, though, we prefer to be more conservative in our inlining in order to be able to better detect CSEs.

Implementations

impl NormalizeLets

pub fn new(inline_mfp: bool) -> NormalizeLets

Construct a new NormalizeLets instance with the given inline_mfp.

impl NormalizeLets

pub fn action( &self, relation: &mut MirRelationExpr, features: &OptimizerFeatures, ) -> Result<(), TransformError>

Normalize Let and LetRec bindings in relation.

Mechanically, action first renumbers all bindings, erroring if any shadowing is encountered. It then promotes all Let and LetRec expressions to the roots of their expressions, fusing Let bindings into containing LetRec bindings, but leaving stacked LetRec bindings unfused to each other (for reasons of correctness). It then considers potential inlining in each LetRec scope. Lastly, it refreshes the types of each Get operator, erroring if any scalar types have changed but updating nullability and keys.

We then perform a final renumbering.

Trait Implementations

impl Debug for NormalizeLets

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Transform for NormalizeLets

fn transform( &self, relation: &mut MirRelationExpr, ctx: &mut TransformCtx<'_>, ) -> Result<(), TransformError>

Transform a relation into a functionally equivalent relation.

fn debug(&self) -> String

A string describing the transform.