Enum ExpectedVersion 

pub enum ExpectedVersion {
    NoStream,
    Exact(u64),
    Any,
}

Optimistic concurrency control contract for EventStore::append.

The caller declares which sequence number they expect the stream to be at. The store atomically checks this before writing; a mismatch means a concurrent writer modified the stream and the caller must reload and retry.

Variants

NoStream

The stream must not exist yet (sequence number 0).

Exact(u64)

The stream must be at exactly this sequence number.

Any

Skip the concurrency check entirely.

Do not use in production workflow append paths. Any silently accepts any write regardless of concurrent modifications, which can produce duplicate or interleaved events in a stream.

Legitimate uses: MigrationRunner (bulk admin rewrites), snapshot-accelerated store internals, and test scaffolding where the caller owns all write access by construction.

For normal workflow event appends always use ExpectedVersion::NoStream (first event) or ExpectedVersion::Exact (subsequent events).

Trait Implementations

impl Clone for ExpectedVersion

fn clone(&self) -> ExpectedVersion

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ExpectedVersion

impl Debug for ExpectedVersion

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

Formats the value using the given formatter.

impl Eq for ExpectedVersion

impl PartialEq for ExpectedVersion

fn eq(&self, other: &ExpectedVersion) -> 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 StructuralPartialEq for ExpectedVersion