Enum Precondition 

pub enum Precondition {
    IfAbsent,
    IfMatch(String),
}

Precondition for a conditional write (ObjectStore::put_if).

Maps onto S3/R2 conditional-write headers so a caller can perform a linearizable compare-and-swap on a single object — e.g. the global tenant→cell pointer in W243 — without any external lock or consensus.

Variants

IfAbsent

Write only if no object exists at the key yet (create-only). Wire form: If-None-Match: *. Fails with Error::PreconditionFailed if any object already exists at the key.

IfMatch(String)

Write only if the current object’s ETag equals this value (optimistic concurrency). Wire form: If-Match: <etag>. Fails with Error::PreconditionFailed if the stored ETag differs or the key is absent. The comparand is an ETag returned by a prior ObjectStore::put_if or ObjectStore::etag.

Trait Implementations

impl Clone for Precondition

fn clone(&self) -> Precondition

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Precondition

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

Formats the value using the given formatter.