Struct IdFilter 

pub struct IdFilter<T> { /* private fields */ }

Available on crate feature utils only.

Exact-match filter for ID columns.

• Empty set: generates no WHERE clause.
• Single ID: generates col = ?.
• Multiple IDs: generates col IN (SELECT value FROM json_each(?)) with a JSON array parameter.

deref() exposes the inner HashSet<T>, useful for inspecting added IDs.

Implementations

impl<T> IdFilter<T>

where T: Hash + PartialEq + Eq + ToSql + Serialize + Display + Clone + 'static,

pub fn new(col: &'static str) -> Self

Create an empty filter for the given column.

pub fn insert(&mut self, id: T) -> &mut Self

Add a single ID to the match set.

pub fn extend(&mut self, ids: impl IntoIterator<Item = T>) -> &mut Self

Add multiple IDs to the match set.

pub fn build_sql<U>(&self, sql: RawSql<U>) -> RawSql<U>

Translate the current ID set into a SQL WHERE condition and write it into sql.

Methods from Deref<Target = HashSet<T>>

pub fn capacity(&self) -> usize

Returns the number of elements the set can hold without reallocating.

Examples

use std::collections::HashSet;
let set: HashSet<i32> = HashSet::with_capacity(100);
assert!(set.capacity() >= 100);

pub fn iter(&self) -> Iter<'_, T>

An iterator visiting all elements in arbitrary order. The iterator element type is &'a T.

Examples

use std::collections::HashSet;
let mut set = HashSet::new();
set.insert("a");
set.insert("b");

// Will print in an arbitrary order.
for x in set.iter() {
    println!("{x}");
}

Performance

In the current implementation, iterating over set takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

pub fn len(&self) -> usize

Returns the number of elements in the set.

Examples

use std::collections::HashSet;

let mut v = HashSet::new();
assert_eq!(v.len(), 0);
v.insert(1);
assert_eq!(v.len(), 1);

pub fn is_empty(&self) -> bool

Returns true if the set contains no elements.

Examples

use std::collections::HashSet;

let mut v = HashSet::new();
assert!(v.is_empty());
v.insert(1);
assert!(!v.is_empty());

pub fn hasher(&self) -> &S

Returns a reference to the set’s BuildHasher.

Examples

use std::collections::HashSet;
use std::hash::RandomState;

let hasher = RandomState::new();
let set: HashSet<i32> = HashSet::with_hasher(hasher);
let hasher: &RandomState = set.hasher();

pub fn difference<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> Difference<'a, T, S, A>

Visits the values representing the difference, i.e., the values that are in self but not in other.

Examples

use std::collections::HashSet;
let a = HashSet::from([1, 2, 3]);
let b = HashSet::from([4, 2, 3, 4]);

// Can be seen as `a - b`.
for x in a.difference(&b) {
    println!("{x}"); // Print 1
}

let diff: HashSet<_> = a.difference(&b).collect();
assert_eq!(diff, [1].iter().collect());

// Note that difference is not symmetric,
// and `b - a` means something else:
let diff: HashSet<_> = b.difference(&a).collect();
assert_eq!(diff, [4].iter().collect());

pub fn symmetric_difference<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> SymmetricDifference<'a, T, S, A>

Visits the values representing the symmetric difference, i.e., the values that are in self or in other but not in both.

Examples

use std::collections::HashSet;
let a = HashSet::from([1, 2, 3]);
let b = HashSet::from([4, 2, 3, 4]);

// Print 1, 4 in arbitrary order.
for x in a.symmetric_difference(&b) {
    println!("{x}");
}

let diff1: HashSet<_> = a.symmetric_difference(&b).collect();
let diff2: HashSet<_> = b.symmetric_difference(&a).collect();

assert_eq!(diff1, diff2);
assert_eq!(diff1, [1, 4].iter().collect());

pub fn intersection<'a>( &'a self, other: &'a HashSet<T, S, A>, ) -> Intersection<'a, T, S, A>

Visits the values representing the intersection, i.e., the values that are both in self and other.

When an equal element is present in self and other then the resulting Intersection may yield references to one or the other. This can be relevant if T contains fields which are not compared by its Eq implementation, and may hold different value between the two equal copies of T in the two sets.

Examples

use std::collections::HashSet;
let a = HashSet::from([1, 2, 3]);
let b = HashSet::from([4, 2, 3, 4]);

// Print 2, 3 in arbitrary order.
for x in a.intersection(&b) {
    println!("{x}");
}

let intersection: HashSet<_> = a.intersection(&b).collect();
assert_eq!(intersection, [2, 3].iter().collect());

pub fn union<'a>(&'a self, other: &'a HashSet<T, S, A>) -> Union<'a, T, S, A>

Visits the values representing the union, i.e., all the values in self or other, without duplicates.

Examples

use std::collections::HashSet;
let a = HashSet::from([1, 2, 3]);
let b = HashSet::from([4, 2, 3, 4]);

// Print 1, 2, 3, 4 in arbitrary order.
for x in a.union(&b) {
    println!("{x}");
}

let union: HashSet<_> = a.union(&b).collect();
assert_eq!(union, [1, 2, 3, 4].iter().collect());

pub fn contains<Q>(&self, value: &Q) -> bool

where T: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns true if the set contains a value.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use std::collections::HashSet;

let set = HashSet::from([1, 2, 3]);
assert_eq!(set.contains(&1), true);
assert_eq!(set.contains(&4), false);

pub fn get<Q>(&self, value: &Q) -> Option<&T>

where T: Borrow<Q>, Q: Hash + Eq + ?Sized,

Returns a reference to the value in the set, if any, that is equal to the given value.

The value may be any borrowed form of the set’s value type, but Hash and Eq on the borrowed form must match those for the value type.

Examples

use std::collections::HashSet;

let set = HashSet::from([1, 2, 3]);
assert_eq!(set.get(&2), Some(&2));
assert_eq!(set.get(&4), None);

pub fn is_disjoint(&self, other: &HashSet<T, S, A>) -> bool

Returns true if self has no elements in common with other. This is equivalent to checking for an empty intersection.

Examples

use std::collections::HashSet;

let a = HashSet::from([1, 2, 3]);
let mut b = HashSet::new();

assert_eq!(a.is_disjoint(&b), true);
b.insert(4);
assert_eq!(a.is_disjoint(&b), true);
b.insert(1);
assert_eq!(a.is_disjoint(&b), false);

pub fn is_subset(&self, other: &HashSet<T, S, A>) -> bool

Returns true if the set is a subset of another, i.e., other contains at least all the values in self.

Examples

use std::collections::HashSet;

let sup = HashSet::from([1, 2, 3]);
let mut set = HashSet::new();

assert_eq!(set.is_subset(&sup), true);
set.insert(2);
assert_eq!(set.is_subset(&sup), true);
set.insert(4);
assert_eq!(set.is_subset(&sup), false);

pub fn is_superset(&self, other: &HashSet<T, S, A>) -> bool

Returns true if the set is a superset of another, i.e., self contains at least all the values in other.

Examples

use std::collections::HashSet;

let sub = HashSet::from([1, 2]);
let mut set = HashSet::new();

assert_eq!(set.is_superset(&sub), false);

set.insert(0);
set.insert(1);
assert_eq!(set.is_superset(&sub), false);

set.insert(2);
assert_eq!(set.is_superset(&sub), true);

Trait Implementations

impl<T: Debug> Debug for IdFilter<T>

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

Formats the value using the given formatter.

impl<T> Deref for IdFilter<T>

type Target = HashSet<T>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.