Enum Presence 

pub enum Presence {
    In,
    NotIn,
}

Which side of an index’s answer a Op::Restrict keeps.

Two operators in one, because they are one delta rule read in two directions: the same probe, the same reverse index, the same cost, and a program that shows both halves of a partition shares one index between them (§99.5 decision 4).

Variants

In

map_contains(m, k(x)) — kept when the index holds the key. The intersection by key, which is a semi-join.

NotIn

not map_contains(m, k(x)) — kept when it does not. The difference by key, which is an anti-join, and §99.4’s one missing row that a program in the tree was already paying for.

Implementations

impl Presence

pub fn keeps(self, present: bool) -> bool

Whether an index holding the key (or not holding it) keeps the row.

pub fn name(self) -> &'static str

The name that reaches a sharing key and beck explain query.

Trait Implementations

impl Clone for Presence

fn clone(&self) -> Presence

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Presence

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

Formats the value using the given formatter.

impl PartialEq for Presence

fn eq(&self, other: &Presence) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Presence

impl Eq for Presence

impl StructuralPartialEq for Presence