Struct transform::projection_pushdown::ProjectionPushdown

pub struct ProjectionPushdown;

Pushes projections down through other operators.

Implementations

impl ProjectionPushdown

pub fn action(
    &self,
    relation: &mut MirRelationExpr,
    desired_projection: &Vec<usize>,
    gets: &mut HashMap<Id, BTreeSet<usize>>
)

Pushes the desired_projection down through relation.

This action transforms relation to a MirRelationExpr equivalent to relation.project(desired_projection).

desired_projection is expected to consist of unique columns.

pub fn update_projection_around_get(
    &self,
    relation: &mut MirRelationExpr,
    applied_projections: &HashMap<Id, Vec<usize>>
)

When we push the desired_value_projection at value, the columns returned by Get(get_id) will change, so we need to permute Projects around Get(get_id).

Trait Implementations

impl Debug for ProjectionPushdown

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

Formats the value using the given formatter.

impl Transform for ProjectionPushdown

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.