Struct AppendCondition 

pub struct AppendCondition {
    pub fail_if_events_match: Query,
    pub after: Position,
    pub fail_if_exists: Option<Query>,
}

The guard on an append call: two independent checks, OR’d, so the append is rejected if either fires.

The boundary check ignores everything at or before after and rejects the append if anything matching fail_if_events_match landed since. after is the highest position the client observed while building its decision model, which may be higher than the last matching event’s position. Positions are 1-based, so after = Position::ZERO (the default) means “consider the whole log”: the spec’s “omit after” case, i.e. fail if any event matches (the uniqueness-guard pattern).

The optional existence check (fail_if_exists) rejects the append if any event anywhere matches its query, independent of after (an implicit after = 0). It is the idempotency/dedupe primitive: assert a key is globally absent even when the boundary legitimately advanced past events the decision read, which a single after cannot express. A conflict from this clause is reported distinctly from a boundary conflict (the engine’s ConflictClause), so a client can treat “already applied” differently from “boundary moved, rebuild and retry”.

This type only holds the condition. Evaluating it (position filtering plus the match predicate over the durable suffix) is the engine’s job.

Fields

fail_if_events_match: Query

Boundary check: reject the append if any event after after matches this query.

after: Position

Ignore everything at or before this position for the boundary check. Position::ZERO means the whole log.

fail_if_exists: Option<Query>

Optional existence check: reject the append if any event anywhere (implicit after = 0) matches this query. None disables it.

Implementations

impl AppendCondition

pub fn new(fail_if_events_match: Query) -> Self

A condition checking the whole log (after = Position::ZERO): fail if any event matches.

pub fn exists_only(query: Query) -> Self

A condition with no boundary check, only the existence clause: fail the append if any event anywhere matches query. The pure idempotency/dedupe guard, without a decision boundary. Equivalent to AppendCondition::new(Query::items([])).fail_if_exists(query) (an empty boundary matches nothing), without the empty-boundary boilerplate.

pub fn after(self, after: Position) -> Self

Sets the exclusive lower bound for the boundary check: only events strictly after after are checked.

pub fn fail_if_exists(self, query: Query) -> Self

Adds the existence check: fail the append if any event anywhere (implicit after = 0) matches query, independent of the boundary. The idempotency/dedupe guard.

Trait Implementations

impl Clone for AppendCondition

fn clone(&self) -> AppendCondition

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for AppendCondition

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

Formats the value using the given formatter.

impl Eq for AppendCondition

impl PartialEq for AppendCondition

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for AppendCondition