Struct mz_transform::semijoin_idempotence::Replacement

struct Replacement {
    id: Id,
    columns: Vec<(usize, usize, usize)>,
    replacement: MirRelationExpr,
}

A restricted form of a semijoin idempotence information.

A Replacement may be offered up by any MirRelationExpr, meant to be B from above or similar, and indicates that the offered expression can be projected onto columns such that it then exactly equals a column projection of Get{id} semijoin replacement. Specifically, the columns member lists indexes (a, b, c) where column b of the offering expression corresponds to columns a in Get{id} and c in replacement, and for which the semijoin requires a = c. The values of the projection of the offering expression onto the b indexes exactly equal the intersection of the projection of Get{id} onto the a indexes and the projection of replacement onto the c columns.

Fields

id: Id

columns: Vec<(usize, usize, usize)>

replacement: MirRelationExpr

Trait Implementations

impl Clone for Replacement

fn clone(&self) -> Replacement

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Replacement

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

Formats the value using the given formatter.