Crate mz_transform

Transformations for relation expressions.

This crate contains traits, types, and methods suitable for transforming MirRelationExpr types in ways that preserve semantics and improve performance. The core trait is Transform, and many implementors of this trait can be boxed and iterated over. Some common transformation patterns are wrapped as Transform implementors themselves.

The crate also contains the beginnings of whole-dataflow optimization, which uses the same analyses but spanning multiple dataflow elements.

Re-exports

pub use dataflow::optimize_dataflow;

Modules

attribute

Derived attributes framework and definitions.

canonicalize_mfp

Canonicalizes MFPs, performs CSEs, and speeds up certain filters.

column_knowledge

Transformations based on pulling information about individual columns from sources.

cse

Common subexpression elimination.

dataflow

Whole-dataflow optimization

demand

Transformation based on pushing demand information about columns toward sources.

fusion

Transformations that fuse together others of their kind.

inline_let

Install replace certain Get operators with their Let value.

join_implementation

Determines the join implementation for join operators.

map_lifting

Hoist literal values from maps wherever possible.

monotonic

Analysis to identify monotonic collections, especially TopK inputs.

nonnull_requirements

Push non-null requirements toward sources.

nonnullable

Harvests information about non-nullability of columns from sources.

predicate_pushdown

Pushes predicates down through other operators.

projection_extraction

Transform column references in a Map into a Project.

projection_lifting

Hoist projections through operators.

projection_pushdown

Pushes column removal down through other operators.

reduce_elision

Removes Reduce when the input has as unique keys the keys of the reduce.

reduction

Replace operators on constants collections with constant collections.

reduction_pushdown

Tries to convert a reduce around a join to a join of reduces. Also absorbs Map operators into Reduce operators.

redundant_join

Remove redundant collections of distinct elements from joins.

threshold_elision

Remove Threshold operators when we are certain no records have negative multiplicity.

topk_elision

Remove TopK operators with both an offset of zero and no limit.

union_cancel

Detects an input being unioned with its negation and cancels them out

update_let

Re-assign type information and identifiers to each Get to ensure uniqueness of identifiers.

Structs

EmptyIndexOracle

An IndexOracle that knows about no indexes.

Fixpoint

A sequence of transformations iterated some number of times.

FuseAndCollapse

A sequence of transformations that simplify the MirRelationExpr

Optimizer

A naive optimizer for relation expressions.

TransformArgs

Arguments that get threaded through all transforms.

Enums

TransformError

Errors that can occur during a transformation.

Traits

IndexOracle

A trait for a type that can answer questions about what indexes exist.

Transform

Types capable of transforming relation expressions.