Struct ObserverRequirements 

pub struct ObserverRequirements {
    pub needs_before_value: bool,
    pub needs_prev_hlc: bool,
}

Per-observer declaration of which optional fields the backend must populate on a TransactionEvent.

The backend OR’s all registered observers’ requirements and produces exactly the fields some observer wants. Fields nobody needs are skipped — for example, the “previous value” read before commit is expensive (an extra RocksDB get); if neither audit (with capture_state: false) nor replication (today) asks for it, the backend skips that read entirely.

Fields

needs_before_value: bool

Read the existing value at the key (if any) before committing the new write. Costs an extra storage get. Audit with capture_state: true needs this; replication today does not (CRDT merge happens at apply time on the receiver using its local state).

needs_prev_hlc: bool

Look up the HLC timestamp of the existing record at the key (if any) and pass it as prev_hlc for causal predecessor tracking. Cheap because the HLC is stored alongside the record metadata in a known location. Replication needs this for the “this write observed prev HLC X” causal-chain invariant; audit does not.

Implementations

impl ObserverRequirements

pub const fn union(self, other: Self) -> Self

Combine two requirement sets — the OR of all flags. Used by the backend to compute the union of all registered observers’ needs.

Trait Implementations

impl Clone for ObserverRequirements

fn clone(&self) -> ObserverRequirements

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ObserverRequirements

impl Debug for ObserverRequirements

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

Formats the value using the given formatter.

impl Default for ObserverRequirements

fn default() -> ObserverRequirements

Returns the “default value” for a type.