Enum QueryCardinality 

#[non_exhaustive]
pub enum QueryCardinality {
    Single,
    Multiple,
    List,
}

Query cardinality classification.

Indicates how many entities a query typically returns, which affects expected cache hit rate.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Single

Single entity: WHERE id = ? → 1 entity Expected cache hit rate: 91%

Multiple

Multiple entities: WHERE id IN (?, …) → N entities Expected cache hit rate: 88%

List

All entities: WHERE 1=1 or no WHERE → all entities Expected cache hit rate: 60%

Implementations

impl QueryCardinality

pub const fn expected_hit_rate(&self) -> f64

Get expected cache hit rate for this cardinality (0-1).

These values are conservative estimates derived from internal load testing on OLTP-style workloads (small keyspace, high query repetition). They inform cache sizing and eviction strategy decisions and are not guaranteed to reflect production hit rates for a given schema or workload.

To calibrate for your workload, compare the cache_hit_rate metric exposed at /metrics against these values. Operator-specific overrides can be configured via the cache.expected_hit_rates section in fraiseql.toml:

[fraiseql.cache.expected_hit_rates]
single   = 0.85   # default: 0.91
multiple = 0.80   # default: 0.88
list     = 0.55   # default: 0.60

Trait Implementations

impl Clone for QueryCardinality

fn clone(&self) -> QueryCardinality

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for QueryCardinality

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

Formats the value using the given formatter.

impl Ord for QueryCardinality

fn cmp(&self, other: &QueryCardinality) -> 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 QueryCardinality

fn eq(&self, other: &QueryCardinality) -> 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 QueryCardinality

fn partial_cmp(&self, other: &QueryCardinality) -> 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 QueryCardinality

impl Eq for QueryCardinality

impl StructuralPartialEq for QueryCardinality