Struct PlanCache 

pub struct PlanCache { /* private fields */ }

LRU cache for query plans

Recency is tracked by a monotonic clock counter stamped onto each entry’s lru_seq on insert and hit, rather than a Vec<String> that had to be linearly scanned (position() + remove()) on every promotion and removal. Promotion (the cache-hit hot path) is now O(1) and allocation-free; eviction picks the entry with the smallest stamp, which is the exact same victim the old front-of-Vec policy would have chosen for any given access sequence.

Implementations

impl PlanCache

pub fn new(capacity: usize) -> PlanCache

Create a new plan cache with the given capacity

A capacity of 0 is meaningless and unreachable from every call site today. If one ever appears, the LRU keeps a single entry rather than evicting forever (the pre-#2012 code looped indefinitely on it).

pub fn with_ttl(self, ttl: Duration) -> PlanCache

Set the TTL for cache entries

pub fn peek(&self, key: &str) -> Option<&CachedPlan>

Read-only cache probe — no LRU promotion, no mutation.

Use this with a read() lock in the hot query path so concurrent readers don’t serialize on a write lock. Falls back to None when the entry is expired or has a pending replan; the caller must then re-acquire a write() lock and call get() to handle eviction and miss insertion.

pub fn get(&mut self, key: &str) -> Option<&CachedPlan>

Get a cached plan by key

pub fn insert(&mut self, key: String, plan: CachedPlan)

Insert a plan into the cache

pub fn remove(&mut self, key: &str) -> Option<CachedPlan>

Remove an entry from the cache

pub fn invalidate<F>(&mut self, predicate: F)

where F: Fn(&str) -> bool,

Invalidate entries matching a predicate

pub fn clear(&mut self)

Clear all entries

pub fn stats(&self) -> CacheStats

Get cache statistics

pub fn prune_expired(&mut self)

Prune expired entries

pub fn record_observation(&mut self, key: &str, rows_scanned: u64)

Trait Implementations

impl Default for PlanCache

fn default() -> PlanCache

Returns the “default value” for a type.