Struct StatementCache 

pub struct StatementCache { /* private fields */ }

Client-side statement cache using LRU eviction

The cache stores prepared statements keyed by their SQL text. When a statement is retrieved from cache, its cursor ID is preserved, allowing Oracle to skip parsing and use the cached server cursor.

Example

// Statement caching is automatic when enabled via config
let mut config = Config::new("localhost", 1521, "FREEPDB1", "user", "pass");
config.set_stmtcachesize(20);  // Enable with 20 statement cache

let conn = Connection::connect_with_config(config).await?;

// First call: parses SQL, gets cursor_id from Oracle
conn.query("SELECT * FROM users WHERE id = :1", &[Value::Integer(1)]).await?;

// Second call: reuses cached cursor, no re-parsing!
conn.query("SELECT * FROM users WHERE id = :1", &[Value::Integer(2)]).await?;

Implementations

impl StatementCache

pub fn new(max_size: usize) -> Self

Create a new statement cache with the given maximum size

A size of 0 effectively disables caching.

pub fn get(&mut self, sql: &str) -> Option<Statement>

Get a statement from the cache, if available

Returns a clone of the cached statement with preserved cursor_id and metadata. If the cached statement is already in use, returns a fresh statement. Updates LRU ordering on hit.

pub fn put(&mut self, sql: String, statement: Statement)

Store a statement in the cache

DDL statements are never cached. If the cache is full, the least recently used statement is evicted and its cursor ID is queued for closing.

pub fn return_statement(&mut self, sql: &str)

Return a statement to the cache after use

This marks the statement as no longer in use so it can be reused.

pub fn take_cursors_to_close(&mut self) -> Vec<u16>

Get and clear the list of cursor IDs that need to be closed

These cursor IDs should be sent to the server on the next message.

pub fn clear(&mut self)

Clear all cached statements

All cursor IDs are queued for closing. This should be called when the session changes (e.g., DRCP session switch).

pub fn len(&self) -> usize

Get the current number of cached statements

pub fn is_empty(&self) -> bool

Check if the cache is empty

pub fn max_size(&self) -> usize

Get the maximum cache size

Trait Implementations

impl Debug for StatementCache

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

Formats the value using the given formatter.