Struct NumericKey 

pub struct NumericKey { /* private fields */ }

r1039 — an exact-decimal index key, canonical so that representation equality IS value equality.

That property is the whole reason this is a struct rather than the (scaled, scale) pair the value carries. 1.5 and 1.50 are the same NUMERIC (PG18.4: 1.5::numeric = 1.50::numeric is true) and arrive here as (15, 1) and (150, 2). A B-tree keyed on the raw pair would file them apart, so WHERE n = 1.5 would miss a row stored as 1.50 — an index changing the answer, which is the one thing an index may never do. BigNumeric::cmp carries the same warning and declines to implement Ord for exactly this reason; a KEY cannot decline, so it normalizes instead.

Canonical form: significant decimal digits with no leading and no trailing zeros, most significant first, plus the decimal exponent of the leading digit. Zero is the empty digit vector with neg == false and exp == 0, so there is no -0.

Ordering is PG’s, measured: -Infinity < -1 < 0 < 1 < Infinity < NaN, and NaN = NaN.

Implementations

impl NumericKey

pub fn from_numeric(scaled: i128, scale: u16, kind: NumericKind) -> Self

The key for a Value::Numeric’s three fields.

Public because the ORDER BY key wants the same canonical form the index key uses: two sort keys that disagree about which of two NUMERICs is larger is the same class of defect as an index that disagrees with a scan, and one definition is how they stay honest.

pub fn from_i128(n: i128) -> Self

The key for an exact integer — no scale, so no rounding.

pub fn from_big(b: &BigNumeric) -> Self

The key for a mantissa that overflowed i128. The two representations of one value land on one key.

pub fn to_f64(&self) -> f64

The f64 this key means, for the one comparison PG defines that way: numeric against float8 demotes the numeric.

Lossy by construction — that is the point, and it is why nothing else uses it.

pub fn digits(&self) -> Vec<u8>

The significant decimal digits, most significant first — the form the catalog codec writes, and the one from_parts reads back.

pub fn parts(&self) -> (u8, bool, i32)

The wire parts, for the catalog codec.

pub fn from_parts(class: u8, neg: bool, exp: i32, digits: &[u8]) -> Option<Self>

Rebuild from the wire parts. Returns None on parts that are not canonical, so a corrupt catalog cannot smuggle in a key whose Eq and Ord disagree.

Trait Implementations

impl Clone for NumericKey

fn clone(&self) -> NumericKey

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for NumericKey

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

Formats the value using the given formatter.

impl Eq for NumericKey

impl Ord for NumericKey

fn cmp(&self, other: &Self) -> 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 NumericKey

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for NumericKey

fn partial_cmp(&self, other: &Self) -> 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 StructuralPartialEq for NumericKey