Enum Consistency 

#[non_exhaustive]
pub enum Consistency {
    Eventual,
    ReadYourWrites,
    Strong,
}

How fresh a query’s view of the materialized index must be. A materialized view is a read model a projector builds by tailing the log, so it is eventually consistent: a record is queryable once the projector has applied it, not the instant it is appended. This level says what the query requires of that lag, and the contract is fail-not-downgrade: a level that cannot be met returns QueryError::Stale rather than silently serving older data.

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.

Eventual

Serve from the index as-is, whatever the projector has applied so far. The default and the cheapest: no wait, best for dashboards and scans where a little lag is fine.

ReadYourWrites

Wait until the projector has applied the source log up to its current head before serving, so a query issued after a publish sees that write (read-your-writes). Bounded: if the projector cannot catch up within the managed deadline the query returns QueryError::Stale instead of downgrading to a stale read. Backend-gated by read_your_writes.

Strong

The strongest level: a linearizable read across replicas. Backend-gated by strong_consistency. Where unavailable the query returns a clean unsupported error. Semantics past read-your-writes are still being pinned, so treat it as read-your-writes plus cross-replica agreement.

Implementations

impl Consistency

pub fn is_eventual(&self) -> bool

Whether this is the default Eventual level (omitted on the wire).

Trait Implementations

impl Clone for Consistency

fn clone(&self) -> Consistency

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Consistency

impl Debug for Consistency

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

Formats the value using the given formatter.

impl Default for Consistency

fn default() -> Consistency

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Consistency

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for Consistency

impl Ord for Consistency

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

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for Consistency

fn partial_cmp(&self, other: &Consistency) -> 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 Serialize for Consistency

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Consistency