mirror of
https://github.com/isar/rusqlite.git
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361 lines
10 KiB
Rust
361 lines
10 KiB
Rust
//! Prepared statements cache for faster execution.
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use crate::raw_statement::RawStatement;
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use crate::{Connection, Result, Statement};
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use lru_cache::LruCache;
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use std::cell::RefCell;
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use std::ops::{Deref, DerefMut};
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use std::sync::Arc;
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impl Connection {
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/// Prepare a SQL statement for execution, returning a previously prepared
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/// (but not currently in-use) statement if one is available. The
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/// returned statement will be cached for reuse by future calls to
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/// `prepare_cached` once it is dropped.
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///
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/// ```rust,no_run
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/// # use rusqlite::{Connection, Result};
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/// fn insert_new_people(conn: &Connection) -> Result<()> {
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/// {
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/// let mut stmt = conn.prepare_cached("INSERT INTO People (name) VALUES (?)")?;
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/// stmt.execute(&["Joe Smith"])?;
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/// }
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/// {
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/// // This will return the same underlying SQLite statement handle without
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/// // having to prepare it again.
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/// let mut stmt = conn.prepare_cached("INSERT INTO People (name) VALUES (?)")?;
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/// stmt.execute(&["Bob Jones"])?;
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/// }
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/// Ok(())
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/// }
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/// ```
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///
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/// # Failure
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///
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/// Will return `Err` if `sql` cannot be converted to a C-compatible string
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/// or if the underlying SQLite call fails.
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pub fn prepare_cached(&self, sql: &str) -> Result<CachedStatement<'_>> {
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self.cache.get(self, sql)
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}
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/// Set the maximum number of cached prepared statements this connection
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/// will hold. By default, a connection will hold a relatively small
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/// number of cached statements. If you need more, or know that you
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/// will not use cached statements, you
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/// can set the capacity manually using this method.
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pub fn set_prepared_statement_cache_capacity(&self, capacity: usize) {
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self.cache.set_capacity(capacity)
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}
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/// Remove/finalize all prepared statements currently in the cache.
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pub fn flush_prepared_statement_cache(&self) {
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self.cache.flush()
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}
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}
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/// Prepared statements LRU cache.
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#[derive(Debug)]
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pub struct StatementCache(RefCell<LruCache<Arc<str>, RawStatement>>);
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/// Cacheable statement.
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///
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/// Statement will return automatically to the cache by default.
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/// If you want the statement to be discarded, call `discard()` on it.
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pub struct CachedStatement<'conn> {
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stmt: Option<Statement<'conn>>,
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cache: &'conn StatementCache,
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}
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impl<'conn> Deref for CachedStatement<'conn> {
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type Target = Statement<'conn>;
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fn deref(&self) -> &Statement<'conn> {
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self.stmt.as_ref().unwrap()
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}
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}
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impl<'conn> DerefMut for CachedStatement<'conn> {
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fn deref_mut(&mut self) -> &mut Statement<'conn> {
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self.stmt.as_mut().unwrap()
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}
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}
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impl Drop for CachedStatement<'_> {
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#[allow(unused_must_use)]
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fn drop(&mut self) {
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if let Some(stmt) = self.stmt.take() {
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self.cache.cache_stmt(unsafe { stmt.into_raw() });
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}
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}
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}
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impl CachedStatement<'_> {
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fn new<'conn>(stmt: Statement<'conn>, cache: &'conn StatementCache) -> CachedStatement<'conn> {
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CachedStatement {
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stmt: Some(stmt),
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cache,
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}
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}
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/// Discard the statement, preventing it from being returned to its
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/// `Connection`'s collection of cached statements.
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pub fn discard(mut self) {
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self.stmt = None;
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}
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}
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impl StatementCache {
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/// Create a statement cache.
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pub fn with_capacity(capacity: usize) -> StatementCache {
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StatementCache(RefCell::new(LruCache::new(capacity)))
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}
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fn set_capacity(&self, capacity: usize) {
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self.0.borrow_mut().set_capacity(capacity)
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}
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// Search the cache for a prepared-statement object that implements `sql`.
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// If no such prepared-statement can be found, allocate and prepare a new one.
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//
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// # Failure
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//
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// Will return `Err` if no cached statement can be found and the underlying
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// SQLite prepare call fails.
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fn get<'conn>(
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&'conn self,
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conn: &'conn Connection,
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sql: &str,
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) -> Result<CachedStatement<'conn>> {
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let trimmed = sql.trim();
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let mut cache = self.0.borrow_mut();
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let stmt = match cache.remove(trimmed) {
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Some(raw_stmt) => Ok(Statement::new(conn, raw_stmt)),
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None => conn.prepare(trimmed),
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};
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stmt.map(|mut stmt| {
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stmt.stmt.set_statement_cache_key(trimmed);
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CachedStatement::new(stmt, self)
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})
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}
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// Return a statement to the cache.
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fn cache_stmt(&self, stmt: RawStatement) {
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if stmt.is_null() {
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return;
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}
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let mut cache = self.0.borrow_mut();
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stmt.clear_bindings();
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if let Some(sql) = stmt.statement_cache_key() {
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cache.insert(sql, stmt);
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} else {
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debug_assert!(
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false,
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"bug in statement cache code, statement returned to cache that without key"
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);
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}
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}
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fn flush(&self) {
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let mut cache = self.0.borrow_mut();
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cache.clear()
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}
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}
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#[cfg(test)]
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mod test {
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use super::StatementCache;
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use crate::{Connection, NO_PARAMS};
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use fallible_iterator::FallibleIterator;
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impl StatementCache {
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fn clear(&self) {
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self.0.borrow_mut().clear();
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}
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fn len(&self) -> usize {
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self.0.borrow().len()
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}
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fn capacity(&self) -> usize {
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self.0.borrow().capacity()
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}
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}
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#[test]
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fn test_cache() {
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let db = Connection::open_in_memory().unwrap();
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let cache = &db.cache;
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let initial_capacity = cache.capacity();
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assert_eq!(0, cache.len());
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assert!(initial_capacity > 0);
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let sql = "PRAGMA schema_version";
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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cache.clear();
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assert_eq!(0, cache.len());
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assert_eq!(initial_capacity, cache.capacity());
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}
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#[test]
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fn test_set_capacity() {
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let db = Connection::open_in_memory().unwrap();
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let cache = &db.cache;
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let sql = "PRAGMA schema_version";
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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db.set_prepared_statement_cache_capacity(0);
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assert_eq!(0, cache.len());
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(0, cache.len());
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db.set_prepared_statement_cache_capacity(8);
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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}
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#[test]
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fn test_discard() {
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let db = Connection::open_in_memory().unwrap();
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let cache = &db.cache;
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let sql = "PRAGMA schema_version";
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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stmt.discard();
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}
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assert_eq!(0, cache.len());
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}
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#[test]
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fn test_ddl() {
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let db = Connection::open_in_memory().unwrap();
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db.execute_batch(
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r#"
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CREATE TABLE foo (x INT);
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INSERT INTO foo VALUES (1);
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"#,
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)
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.unwrap();
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let sql = "SELECT * FROM foo";
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(
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Ok(Some(1i32)),
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stmt.query(NO_PARAMS).unwrap().map(|r| r.get(0)).next()
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);
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}
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db.execute_batch(
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r#"
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ALTER TABLE foo ADD COLUMN y INT;
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UPDATE foo SET y = 2;
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"#,
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)
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.unwrap();
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(
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Ok(Some((1i32, 2i32))),
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stmt.query(NO_PARAMS)
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.unwrap()
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.map(|r| Ok((r.get(0)?, r.get(1)?)))
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.next()
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);
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}
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}
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#[test]
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fn test_connection_close() {
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let conn = Connection::open_in_memory().unwrap();
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conn.prepare_cached("SELECT * FROM sqlite_master;").unwrap();
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conn.close().expect("connection not closed");
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}
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#[test]
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fn test_cache_key() {
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let db = Connection::open_in_memory().unwrap();
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let cache = &db.cache;
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assert_eq!(0, cache.len());
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//let sql = " PRAGMA schema_version; -- comment";
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let sql = "PRAGMA schema_version; ";
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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{
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let mut stmt = db.prepare_cached(sql).unwrap();
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assert_eq!(0, cache.len());
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assert_eq!(
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0,
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stmt.query_row(NO_PARAMS, |r| r.get::<_, i64>(0)).unwrap()
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);
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}
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assert_eq!(1, cache.len());
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}
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#[test]
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fn test_empty_stmt() {
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let conn = Connection::open_in_memory().unwrap();
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conn.prepare_cached("").unwrap();
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}
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}
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