Crate transform

Transformations for relation expressions.

This crate contains traits, types, and methods suitable for transforming RelationExpr 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

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.
empty_map	Remove empty Map operators.
fusion	Transformations that fuse together others of their kind.
inline_let	Install replace certain Get operators with their Let value.
join_elision	Removes unit collections from joins, and joins with fewer than two inputs.
join_implementation	Determines the join implementation for join operators.
map_lifting	Hoist literal values from maps wherever possible.
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.
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	Preliminary work on reduction push-down.
redundant_join	Remove redundant collections of distinct elements from joins.
split_predicates	Transforms predicates of the form "A and B" into two: "A" and "B".
topk_elision	Remove TopK operators with both an offset of zero and no limit.
update_let	Re-assign type information and identifiers to each Get to ensure uniqueness of identifiers.

Structs

Fixpoint	A sequence of transformations iterated some number of times.
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

Transform

Types capable of transforming relation expressions.