Struct SnapshotCache 

pub struct SnapshotCache { /* private fields */ }

Per-session snapshot cache. Owned by the session struct; not thread-shared (one session = one user, one cache).

Implementations

impl SnapshotCache

pub fn new() -> SnapshotCache

New empty cache. Initialises to “no cached snapshot, last seen counter is 0”.

pub fn try_reuse(&self) -> Option<SnapshotId>

Try to reuse the cached snapshot. Returns Some(id) when (a) we have a cached snapshot AND (b) the global counter hasn’t advanced since we cached it. Returns None otherwise — the caller must fetch a fresh one.

pub fn cache(&mut self, snapshot: SnapshotId)

Stash a freshly-fetched snapshot. Records the current global counter so a later try_reuse can validate it hasn’t been invalidated by an intervening commit.

pub fn invalidate(&mut self)

Force-invalidate the cache. Used when the session knows it just performed a write — even if try_reuse would otherwise return the cached snapshot, the write makes it stale for self-visibility.

pub fn staleness(&self) -> u64

Diagnostic: how many bumps have we missed? Difference between the global counter and our last-seen value. Used by EXPLAIN / metrics to track reuse effectiveness.

Trait Implementations

impl Debug for SnapshotCache

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

Formats the value using the given formatter.

impl Default for SnapshotCache

fn default() -> SnapshotCache

Returns the “default value” for a type.