Enum KeyCompare

pub enum KeyCompare {
    Default,
    Number,
    Custom(fn(_: &[u8], _: &[u8]) -> Ordering),
}

Comparison behavior for Keys.

This determines how the database sorts Keys inside a database Table.

See Key for more info.

Variants

Default

Use the default comparison behavior of the backend.

Currently, both heed and redb use lexicographical comparison by default, i.e. a straight byte comparison.

Number

A by-value number comparison, i.e. 255 < 256.

This behavior is implemented as the default for all number primitives, although some implementations on numbers use KeyCompare::Custom due to internal implementation details of LMDB.

Custom(fn(_: &[u8], _: &[u8]) -> Ordering)

A custom sorting function.

The input of the function is 2 Keys in byte form.

Implementations

impl KeyCompare

pub const fn as_compare_fn<K: Key>(self) -> fn(_: &[u8], _: &[u8]) -> Ordering

Return Self as a pure comparison function.

The returned function expects 2 Keys in byte form as input.

Trait Implementations

impl Clone for KeyCompare

fn clone(&self) -> KeyCompare

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for KeyCompare

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

Formats the value using the given formatter.

impl Default for KeyCompare

fn default() -> KeyCompare

Returns the “default value” for a type.

impl Hash for KeyCompare

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for KeyCompare

fn cmp(&self, other: &KeyCompare) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for KeyCompare

fn eq(&self, other: &KeyCompare) -> 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 PartialOrd for KeyCompare

fn partial_cmp(&self, other: &KeyCompare) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for KeyCompare

impl Eq for KeyCompare

impl StructuralPartialEq for KeyCompare

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes

Size for each variant:

• Default: 0 bytes
• Number: 0 bytes
• Custom: 8 bytes