Struct mz_transform::redundant_join::RedundantJoin

pub struct RedundantJoin { /* private fields */ }

Remove redundant collections of distinct elements from joins.

Implementations

impl RedundantJoin

pub fn action(
    &self,
    relation: &mut MirRelationExpr,
    lets: &mut HashMap<Id, Vec<ProvInfo>>
) -> Result<Vec<ProvInfo>, TransformError>

Remove redundant collections of distinct elements from joins.

This method tracks “provenance” information for each collections, those being column-wise relationships to identified collections (either imported collections, or let-bound collections). These relationships state that when projected on to these columns, the records of the one collection are contained in the records of the identified collection.

This provenance information is then used for the MirRelationExpr::Join variant to remove “redundant” joins, those that can be determined to neither restrict nor augment one of the input relations. Consult the find_redundancy method and its documentation for more detail.

Trait Implementations

impl CheckedRecursion for RedundantJoin

fn recursion_guard(&self) -> &RecursionGuard

Extracts a reference to the recursion guard embedded within the type.

fn checked_recur<F, T, E>(&self, f: F) -> Result<T, E> where
    F: FnOnce(&Self) -> Result<T, E>,
    E: From<RecursionLimitError>, 

Checks whether it is safe to recur and calls f if so.

fn checked_recur_mut<F, T, E>(&mut self, f: F) -> Result<T, E> where
    F: FnOnce(&mut Self) -> Result<T, E>,
    E: From<RecursionLimitError>, 

Like CheckedRecursion::checked_recur, but operates on a mutable reference to Self.

impl Debug for RedundantJoin

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

Formats the value using the given formatter.

impl Default for RedundantJoin

fn default() -> RedundantJoin

Returns the “default value” for a type.

impl Transform for RedundantJoin

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

Transform a relation into a functionally equivalent relation.

fn debug(&self) -> String

A string describing the transform.