Enum AppendCondition

Source

pub enum AppendCondition {
    Min(EventSelector, u64),
    Max(EventSelector, u64),
    Range(EventSelector, Range),
}

Expand description

An append condition for a batch transaction (DCB spec: “Append Condition”).

Append conditions ensure that events matching a selector have revision numbers within specified bounds at the time of transaction.

See: https://dcb.events/specification/

Variants§

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Min(EventSelector, u64)

Events matching selector must have revision >= min.

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Max(EventSelector, u64)

Events matching selector must have revision <= max.

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Range(EventSelector, Range)

Events matching selector must have revision within range.

Implementations§

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impl AppendCondition

Source

pub fn min(selector: EventSelector, revision: u64) -> AppendCondition

Create a MIN condition (events must have revision >= min).

Use this when you want to ensure events exist (min=1) or have been updated to at least a certain revision.

Source

pub fn max(selector: EventSelector, revision: u64) -> AppendCondition

Create a MAX condition (events must have revision <= max).

Use this when you want to ensure events don’t exist yet (max=0) or haven’t changed beyond a known revision (optimistic concurrency).

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pub fn range(selector: EventSelector, range: Range) -> AppendCondition

Create a RANGE condition (events must have revision within range).

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pub fn fail_if_events_match(selector: EventSelector) -> AppendCondition

Create a condition that fails if any events match the selector.

This is the core DCB pattern for ensuring uniqueness. It’s equivalent to max(selector, 0).

See: https://dcb.events/specification/

§Example

use evidentsource_core::domain::{AppendCondition, EventSelector};

let selector = EventSelector::stream_equals("my-stream").unwrap();
let condition = AppendCondition::fail_if_events_match(selector);

Source

pub fn must_not_exist(selector: EventSelector) -> AppendCondition

Require that no events matching the selector exist.

This is a semantic alias for max(selector, 0). Use this when creating new entities to ensure uniqueness.

§Example

use evidentsource_core::domain::{AppendCondition, EventSelector};

let selector = EventSelector::stream_equals("my-stream").unwrap();
let condition = AppendCondition::must_not_exist(selector);

Source

pub fn must_exist(selector: EventSelector) -> AppendCondition

Require that at least one event matching the selector exists.

This is a semantic alias for min(selector, 1). Use this when updating existing entities to ensure they exist.

§Example

use evidentsource_core::domain::{AppendCondition, EventSelector};

let selector = EventSelector::stream_equals("my-stream").unwrap();
let condition = AppendCondition::must_exist(selector);

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pub fn at_revision( selector: EventSelector, revision: u64, ) -> Result<AppendCondition, ConstraintError>

Require events matching the selector to be exactly at a specific revision.

Use this for strict revision checks where you need to ensure the exact state hasn’t changed.

§Errors

Returns ConstraintError::InvalidRange if the revision is invalid for creating a range (this should never happen in practice).

§Example

use evidentsource_core::domain::{AppendCondition, EventSelector};

let selector = EventSelector::stream_equals("my-stream").unwrap();
let condition = AppendCondition::at_revision(selector, 42).unwrap();

Source

pub fn unchanged_since( selector: EventSelector, last_seen_revision: u64, ) -> AppendCondition

Require events matching the selector haven’t changed since a known revision.

This is a semantic alias for max(selector, revision). Use this for optimistic concurrency control where you want to ensure no updates have occurred since you last read the data.

§Example

use evidentsource_core::domain::{AppendCondition, EventSelector};

let selector = EventSelector::stream_equals("my-stream").unwrap();
// Ensure the stream hasn't been modified since revision 42
let condition = AppendCondition::unchanged_since(selector, 42);

Source