Struct codd::expression::Select

pub struct Select<T, E> where
    T: Tuple,
    E: Expression<T>,  { /* fields omitted */ }

Selects tuples of the underlying sub-expression according to a given predicate.

Example:

use codd::{Database, expression::Select};

let mut db = Database::new();
let fruit = db.add_relation::<String>("Fruit").unwrap();

db.insert(&fruit, vec!["Apple".to_string(), "BANANA".to_string(), "cherry".to_string()].into());

let select = Select::new(
    &fruit,
    |t| t.contains('A'), // select predicate
);

assert_eq!(vec!["Apple", "BANANA"], db.evaluate(&select).unwrap().into_tuples());

Implementations

impl<T, E> Select<T, E> where
    T: Tuple,
    E: Expression<T>, 

pub fn new<I, P>(expression: I, predicate: P) -> Self where
    I: IntoExpression<T, E>,
    P: FnMut(&T) -> bool + 'static, 

Creates a new Select expression over expression according to the predicate closure.

pub fn expression(&self) -> &E

Returns a reference to the underlying sub-expression.

Trait Implementations

impl<T: Clone, E: Clone> Clone for Select<T, E> where
    T: Tuple,
    E: Expression<T>, 

fn clone(&self) -> Select<T, E>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T, E> Debug for Select<T, E> where
    T: Tuple,
    E: Expression<T>, 

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

Formats the value using the given formatter.

impl<T, E> Expression<T> for Select<T, E> where
    T: Tuple,
    E: Expression<T>, 

fn visit<V>(&self, visitor: &mut V) where
    V: Visitor, 

Visits this expression by a Visitor.

fn builder(&self) -> Builder<T, Self>

Returns an expression builder over this expression.

impl<T: Tuple> From<Select<T, Mono<T>>> for Mono<T>

fn from(select: Select<T, Mono<T>>) -> Self

Performs the conversion.