Struct RecordPrecondition 

pub struct RecordPrecondition {
    pub capability: String,
    pub key: String,
    pub require_absent: bool,
    pub expected_version: Option<u64>,
    pub expected_epoch: Option<u64>,
    pub expected_lease_id: Option<String>,
}

What must be true of one record for a transaction to commit.

Distinct from AtomicPrecondition, and deliberately so. That one compares the row’s internal operation sequence, and None on it means “this record must not exist”. This one compares the fields a caller can actually read back – the document’s __version, its authority epoch, its lease – which are the same fields single-record CAS compares. Plumbing a caller’s expectedVersion into the sequence check would have compared a document version against a storage sequence: two different numbers that happen to share a name.

Every predicate is optional and only a supplied one is checked. That differs from CAS, where an absent expected_lease_id asserts the record is not leased; here an absent predicate asserts nothing at all. The difference is deliberate – a transaction precondition is a fence the caller opts into, not a full description of the record – and it is why the fields are named expected_* rather than describing a state.

Fields

capability: String

key: String

require_absent: bool

The record must not exist. Mutually exclusive with the predicates below.

expected_version: Option<u64>

The document’s __version, as updateIfVersion compares it.

expected_epoch: Option<u64>

The record’s authority epoch, at /authority/epoch.

expected_lease_id: Option<String>

The id of an unexpired lease held on the record.

Implementations

impl RecordPrecondition

pub fn is_empty(&self) -> bool

True when this precondition asks for nothing, which is a caller error rather than a satisfied fence: a precondition that constrains nothing would read as protection and provide none.

Trait Implementations

impl Clone for RecordPrecondition

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RecordPrecondition

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

Formats the value using the given formatter.

impl Default for RecordPrecondition

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for RecordPrecondition

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for RecordPrecondition

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

where __S: Serializer,

Serialize this value into the given Serde serializer.