Struct StatementCache 

pub struct StatementCache { /* private fields */ }

Two-tier prepared statement cache.

• Tier 1 (HashMap): Pre-registered queries. Never evicted. O(1) lookup.
• Tier 2 (LRU): Ad-hoc queries. Auto-evicted when full. O(1) amortized.

Statements are keyed by SQL text. Each cached statement has a unique server-side name for the PG prepared statement protocol.

Implementations

impl StatementCache

pub fn new() -> Self

Create a new statement cache with the default LRU capacity (256).

pub fn with_capacity(lru_capacity: usize) -> Self

Create a new statement cache with a custom LRU capacity.

pub fn register(&mut self, name: &str, statement: Statement)

Register a statement in Tier 1 (permanent, never evicted).

The name is the user-defined name (also used as the server-side name).

pub fn get_registered(&mut self, name: &str) -> Option<&CachedStatement>

Look up a registered statement by name (Tier 1).

pub fn get_adhoc(&mut self, sql: &str) -> Option<&CachedStatement>

Look up an ad-hoc statement by SQL text (Tier 2).

pub fn insert_adhoc( &mut self, sql: String, statement: Statement, ) -> Option<String>

Insert an ad-hoc statement into Tier 2.

Returns the evicted statement’s server-side name if the cache was full, so the caller can send a Close message to the server.

pub fn record_miss(&mut self)

Record a cache miss.

pub fn lookup_or_miss(&mut self, sql: &str) -> Option<&CachedStatement>

Get the server-side name for an ad-hoc query, or generate one.

Checks Tier 2 first. If not found, records a miss and returns None.

pub fn metrics(&self) -> &CacheMetrics

Get cache metrics.

pub fn registered_count(&self) -> usize

Number of registered (Tier 1) statements.

pub fn adhoc_count(&self) -> usize

Number of cached ad-hoc (Tier 2) statements.

pub fn generate_name(&self) -> String

Generate a unique server-side statement name.

Trait Implementations

impl Default for StatementCache

fn default() -> Self

Returns the “default value” for a type.