Struct ReaderSnapshot 

pub struct ReaderSnapshot {
    pub frozen: Arc<FrozenOverlay>,
    pub base: Option<Arc<MappedBase>>,
    pub deltas: Vec<Arc<CommitDelta>>,
    /* private fields */
}

Lock-free reader snapshot: frozen overlay + optional V8 base + pending delta tail.

Obtained cheaply via crate::SharedDb::reader, which acquires the read lock only long enough to clone the Arc fields. Subsequent query operations run without any lock.

Memory bound: holds at most FOLD_EVERY_K − 1 CommitDelta Arcs in its delta tail; the fold that resets the tail runs synchronously on the write path.

Fields

frozen: Arc<FrozenOverlay>

Most-recent fold of the overlay state.

base: Option<Arc<MappedBase>>

Shared mmap base (zero-copy, Arc-ref-counted). None for legacy stores.

deltas: Vec<Arc<CommitDelta>>

Commits since the last fold, in arrival order. Length ≤ FOLD_EVERY_K − 1.

Implementations

impl ReaderSnapshot

pub fn mask_for_role(&self, role: &str) -> Result<NodeMask>

Resolve a role name to a node visibility mask.

Coherent with Self::query_masked: both read from the same effective state (frozen or cached materialization), so the mask is never stale relative to the query data.

pub fn resolve_key(&self, key: &str) -> Option<u32>

Resolve a node key to its dense id.

Checks the delta tail (via the cached materialization) so that nodes inserted since the last fold are visible.

pub fn query( &self, cypher: &str, params: &BTreeMap<String, Value>, ) -> Result<ResultSet>

Execute a read-only Cypher query over the epoch snapshot.

pub fn query_masked( &self, cypher: &str, params: &BTreeMap<String, Value>, mask: &NodeMask, ) -> Result<ResultSet>

Execute a read-only Cypher query with a node visibility mask.

Returns Err when cypher is a write statement (CREATE / MATCH…SET / DELETE).

pub fn node_info(&self, key: &str) -> Option<NodeInfo>

Live node info from the epoch snapshot. None if key is absent or tombstoned.

pub fn node_edges(&self, key: &str) -> Result<Vec<EdgeInfo>>

Every directed edge incident on key. derived is always false since the reader snapshot has no rule engine.

Unknown key → Err(GraphError::KeyNotFound).

pub fn neighborhood_masked( &self, key: &str, depth: u32, edge_types: Option<&[&str]>, dir: Dir, mask: &NodeMask, ) -> Option<ResultSet>

BFS neighborhood expansion restricted to mask-visible nodes.

Hidden nodes are neither returned nor used as traversal intermediaries (never-leak invariant). Returns None when key does not exist.