Expand description

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.


pub use dataflow::optimize_dataflow;


Derived attributes framework and definitions.
Canonicalizes MFPs, performs CSEs, and speeds up certain filters.
Transformations based on pulling information about individual columns from sources.
Common subexpression elimination.
Whole-dataflow optimization
Transformation based on pushing demand information about columns toward sources.
Transformations that fuse together others of their kind.
Install replace certain Get operators with their Let value.
Determines the join implementation for join operators.
Hoist literal values from maps wherever possible.
Analysis to identify monotonic collections, especially TopK inputs.
Push non-null requirements toward sources.
Harvests information about non-nullability of columns from sources.
Pushes predicates down through other operators.
Transform column references in a Map into a Project.
Hoist projections through operators.
Pushes column removal down through other operators.
Removes Reduce when the input has as unique keys the keys of the reduce.
Replace operators on constants collections with constant collections.
Tries to convert a reduce around a join to a join of reduces. Also absorbs Map operators into Reduce operators.
Remove redundant collections of distinct elements from joins.
Remove Threshold operators when we are certain no records have negative multiplicity.
Remove TopK operators with both an offset of zero and no limit.
Detects an input being unioned with its negation and cancels them out
Re-assign type information and identifiers to each Get to ensure uniqueness of identifiers.


An IndexOracle that knows about no indexes.
A sequence of transformations iterated some number of times.
A sequence of transformations that simplify the MirRelationExpr
A naive optimizer for relation expressions.
Arguments that get threaded through all transforms.


Errors that can occur during a transformation.


A trait for a type that can answer questions about what indexes exist.
Types capable of transforming relation expressions.