Enum Precondition 

pub enum Precondition {
    NodeUnchangedSince {
        key: String,
        expected: u64,
    },
    NodeAbsent {
        key: String,
    },
}

A precondition for a compare-and-set batch write.

All preconditions in a GraphDb::write_batch_cas or crate::SharedDb::submit_batch_cas call are checked atomically before any operation in the batch is applied. If any precondition fails, the entire batch is rejected with GraphError::CasConflict and no WAL frame is written.

Touch definition

A node’s last-change commit (last_changed) is updated when any of the following state-changing WAL records touch it:

• InsertNode / InsertNodeId — the newly-inserted node.
• SetProp / SetPropId / RemoveProp — the property-bearing node.
• InsertEdge / InsertEdgeId / DeleteEdge — both src and dst endpoints (an edge change touches both sides).
• DeleteNode — the node is tombstoned; last_changed returns None for deleted keys so the pre-deletion entry is never observed.

History markers (DerivedEdgeAdded / DerivedEdgeRetracted) are state no-ops. The underlying mutation that triggered rule firing already updated the relevant nodes’ last-change entries. Rule-management records (CreateRule, DeleteRule, RebuildRule) and view/full-text declarations do not touch any node’s last-change.

Variants

NodeUnchangedSince

The node’s last-change commit must equal expected.

Fails with GraphError::CasConflict when:

• The node does not exist (last_changed returns None), or
• The recorded commit seq does not match expected.

Fields

key: String

expected: u64

NodeAbsent

The node must not exist (not inserted, or already deleted).

Fails with GraphError::CasConflict (expected=u64::MAX, actual=last_changed(key).unwrap_or(0)) when the node is live.

Fields

key: String

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.

impl Eq for Precondition

impl PartialEq for Precondition

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Precondition