Preparestmt use LRU Map instead default map (#7435)

* 支持lru淘汰preparestmt cache

* 支持lru淘汰preparestmt cache

* 支持lru淘汰preparestmt cache

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* 只使用lru

* change const export

* Add stmt_store

* refact prepare stmt store

* Rename lru store

* change const export

* ADD UT

* format code and add session level prepare stmt config

* code format according to golinter ci

* ADD UT

---------

Co-authored-by: xiezhaodong <xiezhaodong@bytedance.com>
Co-authored-by: Jinzhu <wosmvp@gmail.com>

gorm.go

@@ -34,6 +34,11 @@ type Config struct {
 	DryRun bool
 	// PrepareStmt executes the given query in cached statement
 	PrepareStmt bool
+	// PrepareStmt cache support LRU expired,
+	// default maxsize=int64 Max value and ttl=1h
+	PrepareStmtMaxSize int
+	PrepareStmtTTL     time.Duration
+
 	// DisableAutomaticPing
 	DisableAutomaticPing bool
 	// DisableForeignKeyConstraintWhenMigrating
@@ -105,6 +110,8 @@ type DB struct {
 type Session struct {
 	DryRun                   bool
 	PrepareStmt              bool
+	PrepareStmtMaxSize       int
+	PrepareStmtTTL           time.Duration
 	NewDB                    bool
 	Initialized              bool
 	SkipHooks                bool
@@ -197,7 +204,7 @@ func Open(dialector Dialector, opts ...Option) (db *DB, err error) {
 	}
 
 	if config.PrepareStmt {
-		preparedStmt := NewPreparedStmtDB(db.ConnPool)
+		preparedStmt := NewPreparedStmtDB(db.ConnPool, config.PrepareStmtMaxSize, config.PrepareStmtTTL)
 		db.cacheStore.Store(preparedStmtDBKey, preparedStmt)
 		db.ConnPool = preparedStmt
 	}
@@ -268,7 +275,7 @@ func (db *DB) Session(config *Session) *DB {
 		if v, ok := db.cacheStore.Load(preparedStmtDBKey); ok {
 			preparedStmt = v.(*PreparedStmtDB)
 		} else {
-			preparedStmt = NewPreparedStmtDB(db.ConnPool)
+			preparedStmt = NewPreparedStmtDB(db.ConnPool, config.PrepareStmtMaxSize, config.PrepareStmtTTL)
 			db.cacheStore.Store(preparedStmtDBKey, preparedStmt)
 		}
 

internal/lru/lru.go

@@ -0,0 +1,493 @@
+package lru
+
+// golang -lru
+// https://github.com/hashicorp/golang-lru
+import (
+	"sync"
+	"time"
+)
+
+// EvictCallback is used to get a callback when a cache entry is evicted
+type EvictCallback[K comparable, V any] func(key K, value V)
+
+// LRU implements a thread-safe LRU with expirable entries.
+type LRU[K comparable, V any] struct {
+	size      int
+	evictList *LruList[K, V]
+	items     map[K]*Entry[K, V]
+	onEvict   EvictCallback[K, V]
+
+	// expirable options
+	mu   sync.Mutex
+	ttl  time.Duration
+	done chan struct{}
+
+	// buckets for expiration
+	buckets []bucket[K, V]
+	// uint8 because it's number between 0 and numBuckets
+	nextCleanupBucket uint8
+}
+
+// bucket is a container for holding entries to be expired
+type bucket[K comparable, V any] struct {
+	entries     map[K]*Entry[K, V]
+	newestEntry time.Time
+}
+
+// noEvictionTTL - very long ttl to prevent eviction
+const noEvictionTTL = time.Hour * 24 * 365 * 10
+
+// because of uint8 usage for nextCleanupBucket, should not exceed 256.
+// casting it as uint8 explicitly requires type conversions in multiple places
+const numBuckets = 100
+
+// NewLRU returns a new thread-safe cache with expirable entries.
+//
+// Size parameter set to 0 makes cache of unlimited size, e.g. turns LRU mechanism off.
+//
+// Providing 0 TTL turns expiring off.
+//
+// Delete expired entries every 1/100th of ttl value. Goroutine which deletes expired entries runs indefinitely.
+func NewLRU[K comparable, V any](size int, onEvict EvictCallback[K, V], ttl time.Duration) *LRU[K, V] {
+	if size < 0 {
+		size = 0
+	}
+	if ttl <= 0 {
+		ttl = noEvictionTTL
+	}
+
+	res := LRU[K, V]{
+		ttl:       ttl,
+		size:      size,
+		evictList: NewList[K, V](),
+		items:     make(map[K]*Entry[K, V]),
+		onEvict:   onEvict,
+		done:      make(chan struct{}),
+	}
+
+	// initialize the buckets
+	res.buckets = make([]bucket[K, V], numBuckets)
+	for i := 0; i < numBuckets; i++ {
+		res.buckets[i] = bucket[K, V]{entries: make(map[K]*Entry[K, V])}
+	}
+
+	// enable deleteExpired() running in separate goroutine for cache with non-zero TTL
+	//
+	// Important: done channel is never closed, so deleteExpired() goroutine will never exit,
+	// it's decided to add functionality to close it in the version later than v2.
+	if res.ttl != noEvictionTTL {
+		go func(done <-chan struct{}) {
+			ticker := time.NewTicker(res.ttl / numBuckets)
+			defer ticker.Stop()
+			for {
+				select {
+				case <-done:
+					return
+				case <-ticker.C:
+					res.deleteExpired()
+				}
+			}
+		}(res.done)
+	}
+	return &res
+}
+
+// Purge clears the cache completely.
+// onEvict is called for each evicted key.
+func (c *LRU[K, V]) Purge() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for k, v := range c.items {
+		if c.onEvict != nil {
+			c.onEvict(k, v.Value)
+		}
+		delete(c.items, k)
+	}
+	for _, b := range c.buckets {
+		for _, ent := range b.entries {
+			delete(b.entries, ent.Key)
+		}
+	}
+	c.evictList.Init()
+}
+
+// Add adds a value to the cache. Returns true if an eviction occurred.
+// Returns false if there was no eviction: the item was already in the cache,
+// or the size was not exceeded.
+func (c *LRU[K, V]) Add(key K, value V) (evicted bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	now := time.Now()
+
+	// Check for existing item
+	if ent, ok := c.items[key]; ok {
+		c.evictList.MoveToFront(ent)
+		c.removeFromBucket(ent) // remove the entry from its current bucket as expiresAt is renewed
+		ent.Value = value
+		ent.ExpiresAt = now.Add(c.ttl)
+		c.addToBucket(ent)
+		return false
+	}
+
+	// Add new item
+	ent := c.evictList.PushFrontExpirable(key, value, now.Add(c.ttl))
+	c.items[key] = ent
+	c.addToBucket(ent) // adds the entry to the appropriate bucket and sets entry.expireBucket
+
+	evict := c.size > 0 && c.evictList.Length() > c.size
+	// Verify size not exceeded
+	if evict {
+		c.removeOldest()
+	}
+	return evict
+}
+
+// Get looks up a key's value from the cache.
+func (c *LRU[K, V]) Get(key K) (value V, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	var ent *Entry[K, V]
+	if ent, ok = c.items[key]; ok {
+		// Expired item check
+		if time.Now().After(ent.ExpiresAt) {
+			return value, false
+		}
+		c.evictList.MoveToFront(ent)
+		return ent.Value, true
+	}
+	return
+}
+
+// Contains checks if a key is in the cache, without updating the recent-ness
+// or deleting it for being stale.
+func (c *LRU[K, V]) Contains(key K) (ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	_, ok = c.items[key]
+	return ok
+}
+
+// Peek returns the key value (or undefined if not found) without updating
+// the "recently used"-ness of the key.
+func (c *LRU[K, V]) Peek(key K) (value V, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	var ent *Entry[K, V]
+	if ent, ok = c.items[key]; ok {
+		// Expired item check
+		if time.Now().After(ent.ExpiresAt) {
+			return value, false
+		}
+		return ent.Value, true
+	}
+	return
+}
+
+// Remove removes the provided key from the cache, returning if the
+// key was contained.
+func (c *LRU[K, V]) Remove(key K) bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if ent, ok := c.items[key]; ok {
+		c.removeElement(ent)
+		return true
+	}
+	return false
+}
+
+// RemoveOldest removes the oldest item from the cache.
+func (c *LRU[K, V]) RemoveOldest() (key K, value V, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if ent := c.evictList.Back(); ent != nil {
+		c.removeElement(ent)
+		return ent.Key, ent.Value, true
+	}
+	return
+}
+
+// GetOldest returns the oldest entry
+func (c *LRU[K, V]) GetOldest() (key K, value V, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if ent := c.evictList.Back(); ent != nil {
+		return ent.Key, ent.Value, true
+	}
+	return
+}
+
+func (c *LRU[K, V]) KeyValues() map[K]V {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	maps := make(map[K]V)
+	now := time.Now()
+	for ent := c.evictList.Back(); ent != nil; ent = ent.PrevEntry() {
+		if now.After(ent.ExpiresAt) {
+			continue
+		}
+		maps[ent.Key] = ent.Value
+		// keys = append(keys, ent.Key)
+	}
+	return maps
+}
+
+// Keys returns a slice of the keys in the cache, from oldest to newest.
+// Expired entries are filtered out.
+func (c *LRU[K, V]) Keys() []K {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	keys := make([]K, 0, len(c.items))
+	now := time.Now()
+	for ent := c.evictList.Back(); ent != nil; ent = ent.PrevEntry() {
+		if now.After(ent.ExpiresAt) {
+			continue
+		}
+		keys = append(keys, ent.Key)
+	}
+	return keys
+}
+
+// Values returns a slice of the values in the cache, from oldest to newest.
+// Expired entries are filtered out.
+func (c *LRU[K, V]) Values() []V {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	values := make([]V, 0, len(c.items))
+	now := time.Now()
+	for ent := c.evictList.Back(); ent != nil; ent = ent.PrevEntry() {
+		if now.After(ent.ExpiresAt) {
+			continue
+		}
+		values = append(values, ent.Value)
+	}
+	return values
+}
+
+// Len returns the number of items in the cache.
+func (c *LRU[K, V]) Len() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.evictList.Length()
+}
+
+// Resize changes the cache size. Size of 0 means unlimited.
+func (c *LRU[K, V]) Resize(size int) (evicted int) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if size <= 0 {
+		c.size = 0
+		return 0
+	}
+	diff := c.evictList.Length() - size
+	if diff < 0 {
+		diff = 0
+	}
+	for i := 0; i < diff; i++ {
+		c.removeOldest()
+	}
+	c.size = size
+	return diff
+}
+
+// Close destroys cleanup goroutine. To clean up the cache, run Purge() before Close().
+// func (c *LRU[K, V]) Close() {
+//	c.mu.Lock()
+//	defer c.mu.Unlock()
+//	select {
+//	case <-c.done:
+//		return
+//	default:
+//	}
+//	close(c.done)
+// }
+
+// removeOldest removes the oldest item from the cache. Has to be called with lock!
+func (c *LRU[K, V]) removeOldest() {
+	if ent := c.evictList.Back(); ent != nil {
+		c.removeElement(ent)
+	}
+}
+
+// removeElement is used to remove a given list element from the cache. Has to be called with lock!
+func (c *LRU[K, V]) removeElement(e *Entry[K, V]) {
+	c.evictList.Remove(e)
+	delete(c.items, e.Key)
+	c.removeFromBucket(e)
+	if c.onEvict != nil {
+		c.onEvict(e.Key, e.Value)
+	}
+}
+
+// deleteExpired deletes expired records from the oldest bucket, waiting for the newest entry
+// in it to expire first.
+func (c *LRU[K, V]) deleteExpired() {
+	c.mu.Lock()
+	bucketIdx := c.nextCleanupBucket
+	timeToExpire := time.Until(c.buckets[bucketIdx].newestEntry)
+	// wait for newest entry to expire before cleanup without holding lock
+	if timeToExpire > 0 {
+		c.mu.Unlock()
+		time.Sleep(timeToExpire)
+		c.mu.Lock()
+	}
+	for _, ent := range c.buckets[bucketIdx].entries {
+		c.removeElement(ent)
+	}
+	c.nextCleanupBucket = (c.nextCleanupBucket + 1) % numBuckets
+	c.mu.Unlock()
+}
+
+// addToBucket adds entry to expire bucket so that it will be cleaned up when the time comes. Has to be called with lock!
+func (c *LRU[K, V]) addToBucket(e *Entry[K, V]) {
+	bucketID := (numBuckets + c.nextCleanupBucket - 1) % numBuckets
+	e.ExpireBucket = bucketID
+	c.buckets[bucketID].entries[e.Key] = e
+	if c.buckets[bucketID].newestEntry.Before(e.ExpiresAt) {
+		c.buckets[bucketID].newestEntry = e.ExpiresAt
+	}
+}
+
+// removeFromBucket removes the entry from its corresponding bucket. Has to be called with lock!
+func (c *LRU[K, V]) removeFromBucket(e *Entry[K, V]) {
+	delete(c.buckets[e.ExpireBucket].entries, e.Key)
+}
+
+// Cap returns the capacity of the cache
+func (c *LRU[K, V]) Cap() int {
+	return c.size
+}
+
+// Entry is an LRU Entry
+type Entry[K comparable, V any] struct {
+	// Next and previous pointers in the doubly-linked list of elements.
+	// To simplify the implementation, internally a list l is implemented
+	// as a ring, such that &l.root is both the next element of the last
+	// list element (l.Back()) and the previous element of the first list
+	// element (l.Front()).
+	next, prev *Entry[K, V]
+
+	// The list to which this element belongs.
+	list *LruList[K, V]
+
+	// The LRU Key of this element.
+	Key K
+
+	// The Value stored with this element.
+	Value V
+
+	// The time this element would be cleaned up, optional
+	ExpiresAt time.Time
+
+	// The expiry bucket item was put in, optional
+	ExpireBucket uint8
+}
+
+// PrevEntry returns the previous list element or nil.
+func (e *Entry[K, V]) PrevEntry() *Entry[K, V] {
+	if p := e.prev; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+// LruList represents a doubly linked list.
+// The zero Value for LruList is an empty list ready to use.
+type LruList[K comparable, V any] struct {
+	root Entry[K, V] // sentinel list element, only &root, root.prev, and root.next are used
+	len  int         // current list Length excluding (this) sentinel element
+}
+
+// Init initializes or clears list l.
+func (l *LruList[K, V]) Init() *LruList[K, V] {
+	l.root.next = &l.root
+	l.root.prev = &l.root
+	l.len = 0
+	return l
+}
+
+// NewList returns an initialized list.
+func NewList[K comparable, V any]() *LruList[K, V] { return new(LruList[K, V]).Init() }
+
+// Length returns the number of elements of list l.
+// The complexity is O(1).
+func (l *LruList[K, V]) Length() int { return l.len }
+
+// Back returns the last element of list l or nil if the list is empty.
+func (l *LruList[K, V]) Back() *Entry[K, V] {
+	if l.len == 0 {
+		return nil
+	}
+	return l.root.prev
+}
+
+// lazyInit lazily initializes a zero List Value.
+func (l *LruList[K, V]) lazyInit() {
+	if l.root.next == nil {
+		l.Init()
+	}
+}
+
+// insert inserts e after at, increments l.len, and returns e.
+func (l *LruList[K, V]) insert(e, at *Entry[K, V]) *Entry[K, V] {
+	e.prev = at
+	e.next = at.next
+	e.prev.next = e
+	e.next.prev = e
+	e.list = l
+	l.len++
+	return e
+}
+
+// insertValue is a convenience wrapper for insert(&Entry{Value: v, ExpiresAt: ExpiresAt}, at).
+func (l *LruList[K, V]) insertValue(k K, v V, expiresAt time.Time, at *Entry[K, V]) *Entry[K, V] {
+	return l.insert(&Entry[K, V]{Value: v, Key: k, ExpiresAt: expiresAt}, at)
+}
+
+// Remove removes e from its list, decrements l.len
+func (l *LruList[K, V]) Remove(e *Entry[K, V]) V {
+	e.prev.next = e.next
+	e.next.prev = e.prev
+	e.next = nil // avoid memory leaks
+	e.prev = nil // avoid memory leaks
+	e.list = nil
+	l.len--
+
+	return e.Value
+}
+
+// move moves e to next to at.
+func (l *LruList[K, V]) move(e, at *Entry[K, V]) {
+	if e == at {
+		return
+	}
+	e.prev.next = e.next
+	e.next.prev = e.prev
+
+	e.prev = at
+	e.next = at.next
+	e.prev.next = e
+	e.next.prev = e
+}
+
+// PushFront inserts a new element e with value v at the front of list l and returns e.
+func (l *LruList[K, V]) PushFront(k K, v V) *Entry[K, V] {
+	l.lazyInit()
+	return l.insertValue(k, v, time.Time{}, &l.root)
+}
+
+// PushFrontExpirable inserts a new expirable element e with Value v at the front of list l and returns e.
+func (l *LruList[K, V]) PushFrontExpirable(k K, v V, expiresAt time.Time) *Entry[K, V] {
+	l.lazyInit()
+	return l.insertValue(k, v, expiresAt, &l.root)
+}
+
+// MoveToFront moves element e to the front of list l.
+// If e is not an element of l, the list is not modified.
+// The element must not be nil.
+func (l *LruList[K, V]) MoveToFront(e *Entry[K, V]) {
+	if e.list != l || l.root.next == e {
+		return
+	}
+	// see comment in List.Remove about initialization of l
+	l.move(e, &l.root)
+}

internal/stmt_store/stmt_store.go

@@ -0,0 +1,182 @@
+package stmt_store
+
+import (
+	"context"
+	"database/sql"
+	"sync"
+	"time"
+
+	"gorm.io/gorm/internal/lru"
+)
+
+type Stmt struct {
+	*sql.Stmt
+	Transaction bool
+	prepared    chan struct{}
+	prepareErr  error
+}
+
+func (stmt *Stmt) Error() error {
+	return stmt.prepareErr
+}
+
+func (stmt *Stmt) Close() error {
+	<-stmt.prepared
+
+	if stmt.Stmt != nil {
+		return stmt.Stmt.Close()
+	}
+	return nil
+}
+
+// Store defines an interface for managing the caching operations of SQL statements (Stmt).
+// This interface provides methods for creating new statements, retrieving all cache keys,
+// getting cached statements, setting cached statements, and deleting cached statements.
+type Store interface {
+	// New creates a new Stmt object and caches it.
+	// Parameters:
+	//   ctx: The context for the request, which can carry deadlines, cancellation signals, etc.
+	//   key: The key representing the SQL query, used for caching and preparing the statement.
+	//   isTransaction: Indicates whether this operation is part of a transaction, which may affect the caching strategy.
+	//   connPool: A connection pool that provides database connections.
+	//   locker: A synchronization lock that is unlocked after initialization to avoid deadlocks.
+	// Returns:
+	//   *Stmt: A newly created statement object for executing SQL operations.
+	//   error: An error if the statement preparation fails.
+	New(ctx context.Context, key string, isTransaction bool, connPool ConnPool, locker sync.Locker) (*Stmt, error)
+
+	// Keys returns a slice of all cache keys in the store.
+	Keys() []string
+
+	// Get retrieves a Stmt object from the store based on the given key.
+	// Parameters:
+	//   key: The key used to look up the Stmt object.
+	// Returns:
+	//   *Stmt: The found Stmt object, or nil if not found.
+	//   bool: Indicates whether the corresponding Stmt object was successfully found.
+	Get(key string) (*Stmt, bool)
+
+	// Set stores the given Stmt object in the store and associates it with the specified key.
+	// Parameters:
+	//   key: The key used to associate the Stmt object.
+	//   value: The Stmt object to be stored.
+	Set(key string, value *Stmt)
+
+	// Delete removes the Stmt object corresponding to the specified key from the store.
+	// Parameters:
+	//   key: The key associated with the Stmt object to be deleted.
+	Delete(key string)
+}
+
+// defaultMaxSize defines the default maximum capacity of the cache.
+// Its value is the maximum value of the int64 type, which means that when the cache size is not specified,
+// the cache can theoretically store as many elements as possible.
+// (1 << 63) - 1 is the maximum value that an int64 type can represent.
+const (
+	defaultMaxSize = (1 << 63) - 1
+	// defaultTTL defines the default time-to-live (TTL) for each cache entry.
+	// When the TTL for cache entries is not specified, each cache entry will expire after 24 hours.
+	defaultTTL = time.Hour * 24
+)
+
+// New creates and returns a new Store instance.
+//
+// Parameters:
+//   - size: The maximum capacity of the cache. If the provided size is less than or equal to 0,
+//     it defaults to defaultMaxSize.
+//   - ttl: The time-to-live duration for each cache entry. If the provided ttl is less than or equal to 0,
+//     it defaults to defaultTTL.
+//
+// This function defines an onEvicted callback that is invoked when a cache entry is evicted.
+// The callback ensures that if the evicted value (v) is not nil, its Close method is called asynchronously
+// to release associated resources.
+//
+// Returns:
+//   - A Store instance implemented by lruStore, which internally uses an LRU cache with the specified size,
+//     eviction callback, and TTL.
+func New(size int, ttl time.Duration) Store {
+	if size <= 0 {
+		size = defaultMaxSize
+	}
+
+	if ttl <= 0 {
+		ttl = defaultTTL
+	}
+
+	onEvicted := func(k string, v *Stmt) {
+		if v != nil {
+			go v.Close()
+		}
+	}
+	return &lruStore{lru: lru.NewLRU[string, *Stmt](size, onEvicted, ttl)}
+}
+
+type lruStore struct {
+	lru *lru.LRU[string, *Stmt]
+}
+
+func (s *lruStore) Keys() []string {
+	return s.lru.Keys()
+}
+
+func (s *lruStore) Get(key string) (*Stmt, bool) {
+	stmt, ok := s.lru.Get(key)
+	if ok && stmt != nil {
+		<-stmt.prepared
+	}
+	return stmt, ok
+}
+
+func (s *lruStore) Set(key string, value *Stmt) {
+	s.lru.Add(key, value)
+}
+
+func (s *lruStore) Delete(key string) {
+	s.lru.Remove(key)
+}
+
+type ConnPool interface {
+	PrepareContext(ctx context.Context, query string) (*sql.Stmt, error)
+}
+
+// New creates a new Stmt object for executing SQL queries.
+// It caches the Stmt object for future use and handles preparation and error states.
+// Parameters:
+//
+//	ctx: Context for the request, used to carry deadlines, cancellation signals, etc.
+//	key: The key representing the SQL query, used for caching and preparing the statement.
+//	isTransaction: Indicates whether this operation is part of a transaction, affecting cache strategy.
+//	conn: A connection pool that provides database connections.
+//	locker: A synchronization lock that is unlocked after initialization to avoid deadlocks.
+//
+// Returns:
+//
+//	*Stmt: A newly created statement object for executing SQL operations.
+//	error: An error if the statement preparation fails.
+func (s *lruStore) New(ctx context.Context, key string, isTransaction bool, conn ConnPool, locker sync.Locker) (_ *Stmt, err error) {
+	// Create a Stmt object and set its Transaction property.
+	// The prepared channel is used to synchronize the statement preparation state.
+	cacheStmt := &Stmt{
+		Transaction: isTransaction,
+		prepared:    make(chan struct{}),
+	}
+	// Cache the Stmt object with the associated key.
+	s.Set(key, cacheStmt)
+	// Unlock after completing initialization to prevent deadlocks.
+	locker.Unlock()
+
+	// Ensure the prepared channel is closed after the function execution completes.
+	defer close(cacheStmt.prepared)
+
+	// Prepare the SQL statement using the provided connection.
+	cacheStmt.Stmt, err = conn.PrepareContext(ctx, key)
+	if err != nil {
+		// If statement preparation fails, record the error and remove the invalid Stmt object from the cache.
+		cacheStmt.prepareErr = err
+		s.Delete(key)
+		return &Stmt{}, err
+	}
+
+	// Return the successfully prepared Stmt object.
+	return cacheStmt, nil
+}

prepare_stmt.go

@@ -7,29 +7,35 @@ import (
 	"errors"
 	"reflect"
 	"sync"
+	"time"
+
+	"gorm.io/gorm/internal/stmt_store"
 )
 
-type Stmt struct {
-	*sql.Stmt
-	Transaction bool
-	prepared    chan struct{}
-	prepareErr  error
-}
-
 type PreparedStmtDB struct {
-	Stmts map[string]*Stmt
+	Stmts stmt_store.Store
 	Mux   *sync.RWMutex
 	ConnPool
 }
 
-func NewPreparedStmtDB(connPool ConnPool) *PreparedStmtDB {
+// NewPreparedStmtDB creates and initializes a new instance of PreparedStmtDB.
+//
+// Parameters:
+// - connPool: A connection pool that implements the ConnPool interface, used for managing database connections.
+// - maxSize: The maximum number of prepared statements that can be stored in the statement store.
+// - ttl: The time-to-live duration for each prepared statement in the store. Statements older than this duration will be automatically removed.
+//
+// Returns:
+// - A pointer to a PreparedStmtDB instance, which manages prepared statements using the provided connection pool and configuration.
+func NewPreparedStmtDB(connPool ConnPool, maxSize int, ttl time.Duration) *PreparedStmtDB {
 	return &PreparedStmtDB{
-		ConnPool: connPool,
-		Stmts:    make(map[string]*Stmt),
-		Mux:      &sync.RWMutex{},
+		ConnPool: connPool,                     // Assigns the provided connection pool to manage database connections.
+		Stmts:    stmt_store.New(maxSize, ttl), // Initializes a new statement store with the specified maximum size and TTL.
+		Mux:      &sync.RWMutex{},              // Sets up a read-write mutex for synchronizing access to the statement store.
 	}
 }
 
+// GetDBConn returns the underlying *sql.DB connection
 func (db *PreparedStmtDB) GetDBConn() (*sql.DB, error) {
 	if sqldb, ok := db.ConnPool.(*sql.DB); ok {
 		return sqldb, nil
@@ -42,98 +48,41 @@ func (db *PreparedStmtDB) GetDBConn() (*sql.DB, error) {
 	return nil, ErrInvalidDB
 }
 
+// Close closes all prepared statements in the store
 func (db *PreparedStmtDB) Close() {
 	db.Mux.Lock()
 	defer db.Mux.Unlock()
 
-	for _, stmt := range db.Stmts {
-		go func(s *Stmt) {
-			// make sure the stmt must finish preparation first
-			<-s.prepared
-			if s.Stmt != nil {
-				_ = s.Close()
-			}
-		}(stmt)
+	for _, key := range db.Stmts.Keys() {
+		db.Stmts.Delete(key)
 	}
-	// setting db.Stmts to nil to avoid further using
-	db.Stmts = nil
 }
 
-func (sdb *PreparedStmtDB) Reset() {
-	sdb.Mux.Lock()
-	defer sdb.Mux.Unlock()
-
-	for _, stmt := range sdb.Stmts {
-		go func(s *Stmt) {
-			// make sure the stmt must finish preparation first
-			<-s.prepared
-			if s.Stmt != nil {
-				_ = s.Close()
-			}
-		}(stmt)
-	}
-	sdb.Stmts = make(map[string]*Stmt)
+// Reset Deprecated use Close instead
+func (db *PreparedStmtDB) Reset() {
+	db.Close()
 }
 
-func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransaction bool, query string) (Stmt, error) {
+func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransaction bool, query string) (_ *stmt_store.Stmt, err error) {
 	db.Mux.RLock()
-	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {
-		db.Mux.RUnlock()
-		// wait for other goroutines prepared
-		<-stmt.prepared
-		if stmt.prepareErr != nil {
-			return Stmt{}, stmt.prepareErr
+	if db.Stmts != nil {
+		if stmt, ok := db.Stmts.Get(query); ok && (!stmt.Transaction || isTransaction) {
+			db.Mux.RUnlock()
+			return stmt, stmt.Error()
 		}
-
-		return *stmt, nil
 	}
 	db.Mux.RUnlock()
 
+	// retry
 	db.Mux.Lock()
-	// double check
-	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {
-		db.Mux.Unlock()
-		// wait for other goroutines prepared
-		<-stmt.prepared
-		if stmt.prepareErr != nil {
-			return Stmt{}, stmt.prepareErr
+	if db.Stmts != nil {
+		if stmt, ok := db.Stmts.Get(query); ok && (!stmt.Transaction || isTransaction) {
+			db.Mux.Unlock()
+			return stmt, stmt.Error()
 		}
-
-		return *stmt, nil
-	}
-	// check db.Stmts first to avoid Segmentation Fault(setting value to nil map)
-	// which cause by calling Close and executing SQL concurrently
-	if db.Stmts == nil {
-		db.Mux.Unlock()
-		return Stmt{}, ErrInvalidDB
-	}
-	// cache preparing stmt first
-	cacheStmt := Stmt{Transaction: isTransaction, prepared: make(chan struct{})}
-	db.Stmts[query] = &cacheStmt
-	db.Mux.Unlock()
-
-	// prepare completed
-	defer close(cacheStmt.prepared)
-
-	// Reason why cannot lock conn.PrepareContext
-	// suppose the maxopen is 1, g1 is creating record and g2 is querying record.
-	// 1. g1 begin tx, g1 is requeue because of waiting for the system call, now `db.ConnPool` db.numOpen == 1.
-	// 2. g2 select lock `conn.PrepareContext(ctx, query)`, now db.numOpen == db.maxOpen , wait for release.
-	// 3. g1 tx exec insert, wait for unlock `conn.PrepareContext(ctx, query)` to finish tx and release.
-	stmt, err := conn.PrepareContext(ctx, query)
-	if err != nil {
-		cacheStmt.prepareErr = err
-		db.Mux.Lock()
-		delete(db.Stmts, query)
-		db.Mux.Unlock()
-		return Stmt{}, err
 	}
 
-	db.Mux.Lock()
-	cacheStmt.Stmt = stmt
-	db.Mux.Unlock()
-
-	return cacheStmt, nil
+	return db.Stmts.New(ctx, query, isTransaction, conn, db.Mux)
 }
 
 func (db *PreparedStmtDB) BeginTx(ctx context.Context, opt *sql.TxOptions) (ConnPool, error) {
@@ -162,10 +111,7 @@ func (db *PreparedStmtDB) ExecContext(ctx context.Context, query string, args ..
 	if err == nil {
 		result, err = stmt.ExecContext(ctx, args...)
 		if errors.Is(err, driver.ErrBadConn) {
-			db.Mux.Lock()
-			defer db.Mux.Unlock()
-			go stmt.Close()
-			delete(db.Stmts, query)
+			db.Stmts.Delete(query)
 		}
 	}
 	return result, err
@@ -176,11 +122,7 @@ func (db *PreparedStmtDB) QueryContext(ctx context.Context, query string, args .
 	if err == nil {
 		rows, err = stmt.QueryContext(ctx, args...)
 		if errors.Is(err, driver.ErrBadConn) {
-			db.Mux.Lock()
-			defer db.Mux.Unlock()
-
-			go stmt.Close()
-			delete(db.Stmts, query)
+			db.Stmts.Delete(query)
 		}
 	}
 	return rows, err
@@ -230,11 +172,7 @@ func (tx *PreparedStmtTX) ExecContext(ctx context.Context, query string, args ..
 	if err == nil {
 		result, err = tx.Tx.StmtContext(ctx, stmt.Stmt).ExecContext(ctx, args...)
 		if errors.Is(err, driver.ErrBadConn) {
-			tx.PreparedStmtDB.Mux.Lock()
-			defer tx.PreparedStmtDB.Mux.Unlock()
-
-			go stmt.Close()
-			delete(tx.PreparedStmtDB.Stmts, query)
+			tx.PreparedStmtDB.Stmts.Delete(query)
 		}
 	}
 	return result, err
@@ -245,11 +183,7 @@ func (tx *PreparedStmtTX) QueryContext(ctx context.Context, query string, args .
 	if err == nil {
 		rows, err = tx.Tx.StmtContext(ctx, stmt.Stmt).QueryContext(ctx, args...)
 		if errors.Is(err, driver.ErrBadConn) {
-			tx.PreparedStmtDB.Mux.Lock()
-			defer tx.PreparedStmtDB.Mux.Unlock()
-
-			go stmt.Close()
-			delete(tx.PreparedStmtDB.Stmts, query)
+			tx.PreparedStmtDB.Stmts.Delete(query)
 		}
 	}
 	return rows, err

tests/go.mod

@@ -1,15 +1,17 @@
 module gorm.io/gorm/tests
 
-go 1.18
+go 1.23.0
+
+toolchain go1.24.2
 
 require (
 	github.com/google/uuid v1.6.0
 	github.com/jinzhu/now v1.1.5
 	github.com/lib/pq v1.10.9
-	github.com/stretchr/testify v1.9.0
+	github.com/stretchr/testify v1.10.0
 	gorm.io/driver/mysql v1.5.7
-	gorm.io/driver/postgres v1.5.10
-	gorm.io/driver/sqlite v1.5.6
+	gorm.io/driver/postgres v1.5.11
+	gorm.io/driver/sqlite v1.5.7
 	gorm.io/driver/sqlserver v1.5.4
 	gorm.io/gorm v1.25.12
 )
@@ -17,7 +19,7 @@ require (
 require (
 	filippo.io/edwards25519 v1.1.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/go-sql-driver/mysql v1.8.1 // indirect
+	github.com/go-sql-driver/mysql v1.9.2 // indirect
 	github.com/golang-sql/civil v0.0.0-20220223132316-b832511892a9 // indirect
 	github.com/golang-sql/sqlexp v0.1.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
@@ -25,12 +27,12 @@ require (
 	github.com/jackc/pgx/v5 v5.7.1 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/kr/text v0.2.0 // indirect
-	github.com/mattn/go-sqlite3 v1.14.24 // indirect
+	github.com/mattn/go-sqlite3 v1.14.28 // indirect
 	github.com/microsoft/go-mssqldb v1.7.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rogpeppe/go-internal v1.12.0 // indirect
-	golang.org/x/crypto v0.29.0 // indirect
-	golang.org/x/text v0.20.0 // indirect
+	golang.org/x/crypto v0.37.0 // indirect
+	golang.org/x/text v0.24.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

tests/lru_test.go

@@ -0,0 +1,561 @@
+package tests_test
+
+import (
+	"crypto/rand"
+	"fmt"
+	"gorm.io/gorm/internal/lru"
+	"math"
+	"math/big"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestLRU_Add_ExistingKey_UpdatesValueAndExpiresAt(t *testing.T) {
+	lru := lru.NewLRU[string, int](10, nil, time.Hour)
+	lru.Add("key1", 1)
+	lru.Add("key1", 2)
+
+	if value, ok := lru.Get("key1"); !ok || value != 2 {
+		t.Errorf("Expected value to be updated to 2, got %v", value)
+	}
+}
+
+func TestLRU_Add_NewKey_AddsEntry(t *testing.T) {
+	lru := lru.NewLRU[string, int](10, nil, time.Hour)
+	lru.Add("key1", 1)
+
+	if value, ok := lru.Get("key1"); !ok || value != 1 {
+		t.Errorf("Expected key1 to be added with value 1, got %v", value)
+	}
+}
+
+func TestLRU_Add_ExceedsSize_RemovesOldest(t *testing.T) {
+	lru := lru.NewLRU[string, int](2, nil, time.Hour)
+	lru.Add("key1", 1)
+	lru.Add("key2", 2)
+	lru.Add("key3", 3)
+
+	if _, ok := lru.Get("key1"); ok {
+		t.Errorf("Expected key1 to be removed, but it still exists")
+	}
+}
+
+func TestLRU_Add_UnlimitedSize_NoEviction(t *testing.T) {
+	lru := lru.NewLRU[string, int](0, nil, time.Hour)
+	lru.Add("key1", 1)
+	lru.Add("key2", 2)
+	lru.Add("key3", 3)
+
+	if _, ok := lru.Get("key1"); !ok {
+		t.Errorf("Expected key1 to exist, but it was evicted")
+	}
+}
+
+func TestLRU_Add_Eviction(t *testing.T) {
+	lru := lru.NewLRU[string, int](0, nil, time.Second*2)
+	lru.Add("key1", 1)
+	lru.Add("key2", 2)
+	lru.Add("key3", 3)
+	time.Sleep(time.Second * 3)
+	if lru.Cap() != 0 {
+		t.Errorf("Expected lru to be empty, but it was not")
+	}
+
+}
+
+func BenchmarkLRU_Rand_NoExpire(b *testing.B) {
+	l := lru.NewLRU[int64, int64](8192, nil, 0)
+
+	trace := make([]int64, b.N*2)
+	for i := 0; i < b.N*2; i++ {
+		trace[i] = getRand(b) % 32768
+	}
+
+	b.ResetTimer()
+
+	var hit, miss int
+	for i := 0; i < 2*b.N; i++ {
+		if i%2 == 0 {
+			l.Add(trace[i], trace[i])
+		} else {
+			if _, ok := l.Get(trace[i]); ok {
+				hit++
+			} else {
+				miss++
+			}
+		}
+	}
+	b.Logf("hit: %d miss: %d ratio: %f", hit, miss, float64(hit)/float64(hit+miss))
+}
+
+func BenchmarkLRU_Freq_NoExpire(b *testing.B) {
+	l := lru.NewLRU[int64, int64](8192, nil, 0)
+
+	trace := make([]int64, b.N*2)
+	for i := 0; i < b.N*2; i++ {
+		if i%2 == 0 {
+			trace[i] = getRand(b) % 16384
+		} else {
+			trace[i] = getRand(b) % 32768
+		}
+	}
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		l.Add(trace[i], trace[i])
+	}
+	var hit, miss int
+	for i := 0; i < b.N; i++ {
+		if _, ok := l.Get(trace[i]); ok {
+			hit++
+		} else {
+			miss++
+		}
+	}
+	b.Logf("hit: %d miss: %d ratio: %f", hit, miss, float64(hit)/float64(hit+miss))
+}
+
+func BenchmarkLRU_Rand_WithExpire(b *testing.B) {
+	l := lru.NewLRU[int64, int64](8192, nil, time.Millisecond*10)
+
+	trace := make([]int64, b.N*2)
+	for i := 0; i < b.N*2; i++ {
+		trace[i] = getRand(b) % 32768
+	}
+
+	b.ResetTimer()
+
+	var hit, miss int
+	for i := 0; i < 2*b.N; i++ {
+		if i%2 == 0 {
+			l.Add(trace[i], trace[i])
+		} else {
+			if _, ok := l.Get(trace[i]); ok {
+				hit++
+			} else {
+				miss++
+			}
+		}
+	}
+	b.Logf("hit: %d miss: %d ratio: %f", hit, miss, float64(hit)/float64(hit+miss))
+}
+
+func BenchmarkLRU_Freq_WithExpire(b *testing.B) {
+	l := lru.NewLRU[int64, int64](8192, nil, time.Millisecond*10)
+
+	trace := make([]int64, b.N*2)
+	for i := 0; i < b.N*2; i++ {
+		if i%2 == 0 {
+			trace[i] = getRand(b) % 16384
+		} else {
+			trace[i] = getRand(b) % 32768
+		}
+	}
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		l.Add(trace[i], trace[i])
+	}
+	var hit, miss int
+	for i := 0; i < b.N; i++ {
+		if _, ok := l.Get(trace[i]); ok {
+			hit++
+		} else {
+			miss++
+		}
+	}
+	b.Logf("hit: %d miss: %d ratio: %f", hit, miss, float64(hit)/float64(hit+miss))
+}
+
+func TestLRUNoPurge(t *testing.T) {
+	lc := lru.NewLRU[string, string](10, nil, 0)
+
+	lc.Add("key1", "val1")
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	v, ok := lc.Peek("key1")
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+	if !lc.Contains("key1") {
+		t.Fatalf("should contain key1")
+	}
+	if lc.Contains("key2") {
+		t.Fatalf("should not contain key2")
+	}
+
+	v, ok = lc.Peek("key2")
+	if v != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+
+	if !reflect.DeepEqual(lc.Keys(), []string{"key1"}) {
+		t.Fatalf("value differs from expected")
+	}
+
+	if lc.Resize(0) != 0 {
+		t.Fatalf("evicted count differs from expected")
+	}
+	if lc.Resize(2) != 0 {
+		t.Fatalf("evicted count differs from expected")
+	}
+	lc.Add("key2", "val2")
+	if lc.Resize(1) != 1 {
+		t.Fatalf("evicted count differs from expected")
+	}
+}
+
+func TestLRUEdgeCases(t *testing.T) {
+	lc := lru.NewLRU[string, *string](2, nil, 0)
+
+	// Adding a nil value
+	lc.Add("key1", nil)
+
+	value, exists := lc.Get("key1")
+	if value != nil || !exists {
+		t.Fatalf("unexpected value or existence flag for key1: value=%v, exists=%v", value, exists)
+	}
+
+	// Adding an entry with the same key but different value
+	newVal := "val1"
+	lc.Add("key1", &newVal)
+
+	value, exists = lc.Get("key1")
+	if value != &newVal || !exists {
+		t.Fatalf("unexpected value or existence flag for key1: value=%v, exists=%v", value, exists)
+	}
+}
+
+func TestLRU_Values(t *testing.T) {
+	lc := lru.NewLRU[string, string](3, nil, 0)
+
+	lc.Add("key1", "val1")
+	lc.Add("key2", "val2")
+	lc.Add("key3", "val3")
+
+	values := lc.Values()
+	if !reflect.DeepEqual(values, []string{"val1", "val2", "val3"}) {
+		t.Fatalf("values differs from expected")
+	}
+}
+
+// func TestExpirableMultipleClose(_ *testing.T) {
+//	lc :=lru.NewLRU[string, string](10, nil, 0)
+//	lc.Close()
+//	// should not panic
+//	lc.Close()
+// }
+
+func TestLRUWithPurge(t *testing.T) {
+	var evicted []string
+	lc := lru.NewLRU(10, func(key string, value string) { evicted = append(evicted, key, value) }, 150*time.Millisecond)
+
+	k, v, ok := lc.GetOldest()
+	if k != "" {
+		t.Fatalf("should be empty")
+	}
+	if v != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+
+	lc.Add("key1", "val1")
+
+	time.Sleep(100 * time.Millisecond) // not enough to expire
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	v, ok = lc.Get("key1")
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+	time.Sleep(200 * time.Millisecond) // expire
+	v, ok = lc.Get("key1")
+	if ok {
+		t.Fatalf("should be false")
+	}
+	if v != "" {
+		t.Fatalf("should be nil")
+	}
+
+	if lc.Len() != 0 {
+		t.Fatalf("length differs from expected")
+	}
+	if !reflect.DeepEqual(evicted, []string{"key1", "val1"}) {
+		t.Fatalf("value differs from expected")
+	}
+
+	// add new entry
+	lc.Add("key2", "val2")
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	k, v, ok = lc.GetOldest()
+	if k != "key2" {
+		t.Fatalf("value differs from expected")
+	}
+	if v != "val2" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+}
+
+func TestLRUWithPurgeEnforcedBySize(t *testing.T) {
+	lc := lru.NewLRU[string, string](10, nil, time.Hour)
+
+	for i := 0; i < 100; i++ {
+		i := i
+		lc.Add(fmt.Sprintf("key%d", i), fmt.Sprintf("val%d", i))
+		v, ok := lc.Get(fmt.Sprintf("key%d", i))
+		if v != fmt.Sprintf("val%d", i) {
+			t.Fatalf("value differs from expected")
+		}
+		if !ok {
+			t.Fatalf("should be true")
+		}
+		if lc.Len() > 20 {
+			t.Fatalf("length should be less than 20")
+		}
+	}
+
+	if lc.Len() != 10 {
+		t.Fatalf("length differs from expected")
+	}
+}
+
+func TestLRUConcurrency(t *testing.T) {
+	lc := lru.NewLRU[string, string](0, nil, 0)
+	wg := sync.WaitGroup{}
+	wg.Add(1000)
+	for i := 0; i < 1000; i++ {
+		go func(i int) {
+			lc.Add(fmt.Sprintf("key-%d", i/10), fmt.Sprintf("val-%d", i/10))
+			wg.Done()
+		}(i)
+	}
+	wg.Wait()
+	if lc.Len() != 100 {
+		t.Fatalf("length differs from expected")
+	}
+}
+
+func TestLRUInvalidateAndEvict(t *testing.T) {
+	var evicted int
+	lc := lru.NewLRU(-1, func(_, _ string) { evicted++ }, 0)
+
+	lc.Add("key1", "val1")
+	lc.Add("key2", "val2")
+
+	val, ok := lc.Get("key1")
+	if !ok {
+		t.Fatalf("should be true")
+	}
+	if val != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if evicted != 0 {
+		t.Fatalf("value differs from expected")
+	}
+
+	lc.Remove("key1")
+	if evicted != 1 {
+		t.Fatalf("value differs from expected")
+	}
+	val, ok = lc.Get("key1")
+	if val != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+}
+
+func TestLoadingExpired(t *testing.T) {
+	lc := lru.NewLRU[string, string](0, nil, time.Millisecond*5)
+
+	lc.Add("key1", "val1")
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	v, ok := lc.Peek("key1")
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+	v, ok = lc.Get("key1")
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+	for {
+		result, ok := lc.Get("key1")
+		if ok && result == "" {
+			t.Fatalf("ok should return a result")
+		}
+		if !ok {
+			break
+		}
+	}
+
+	time.Sleep(time.Millisecond * 100) // wait for expiration reaper
+	if lc.Len() != 0 {
+		t.Fatalf("length differs from expected")
+	}
+
+	v, ok = lc.Peek("key1")
+	if v != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+
+	v, ok = lc.Get("key1")
+	if v != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+}
+
+func TestLRURemoveOldest(t *testing.T) {
+	lc := lru.NewLRU[string, string](2, nil, 0)
+
+	if lc.Cap() != 2 {
+		t.Fatalf("expect cap is 2")
+	}
+
+	k, v, ok := lc.RemoveOldest()
+	if k != "" {
+		t.Fatalf("should be empty")
+	}
+	if v != "" {
+		t.Fatalf("should be empty")
+	}
+	if ok {
+		t.Fatalf("should be false")
+	}
+
+	ok = lc.Remove("non_existent")
+	if ok {
+		t.Fatalf("should be false")
+	}
+
+	lc.Add("key1", "val1")
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	v, ok = lc.Get("key1")
+	if !ok {
+		t.Fatalf("should be true")
+	}
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+
+	if !reflect.DeepEqual(lc.Keys(), []string{"key1"}) {
+		t.Fatalf("value differs from expected")
+	}
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+
+	lc.Add("key2", "val2")
+	if !reflect.DeepEqual(lc.Keys(), []string{"key1", "key2"}) {
+		t.Fatalf("value differs from expected")
+	}
+	if lc.Len() != 2 {
+		t.Fatalf("length differs from expected")
+	}
+
+	k, v, ok = lc.RemoveOldest()
+	if k != "key1" {
+		t.Fatalf("value differs from expected")
+	}
+	if v != "val1" {
+		t.Fatalf("value differs from expected")
+	}
+	if !ok {
+		t.Fatalf("should be true")
+	}
+
+	if !reflect.DeepEqual(lc.Keys(), []string{"key2"}) {
+		t.Fatalf("value differs from expected")
+	}
+	if lc.Len() != 1 {
+		t.Fatalf("length differs from expected")
+	}
+}
+
+func ExampleLRU() {
+	// make cache with 10ms TTL and 5 max keys
+	cache := lru.NewLRU[string, string](5, nil, time.Millisecond*10)
+
+	// set value under key1.
+	cache.Add("key1", "val1")
+
+	// get value under key1
+	r, ok := cache.Get("key1")
+
+	// check for OK value
+	if ok {
+		fmt.Printf("value before expiration is found: %v, value: %q\n", ok, r)
+	}
+
+	// wait for cache to expire
+	time.Sleep(time.Millisecond * 100)
+
+	// get value under key1 after key expiration
+	r, ok = cache.Get("key1")
+	fmt.Printf("value after expiration is found: %v, value: %q\n", ok, r)
+
+	// set value under key2, would evict old entry because it is already expired.
+	cache.Add("key2", "val2")
+
+	fmt.Printf("Cache len: %d\n", cache.Len())
+	// Output:
+	// value before expiration is found: true, value: "val1"
+	// value after expiration is found: false, value: ""
+	// Cache len: 1
+}
+
+func getRand(tb testing.TB) int64 {
+	out, err := rand.Int(rand.Reader, big.NewInt(math.MaxInt64))
+	if err != nil {
+		tb.Fatal(err)
+	}
+	return out.Int64()
+}

tests/prepared_stmt_test.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"sync"
-	"sync/atomic"
 	"testing"
 	"time"
 
@@ -92,6 +91,65 @@ func TestPreparedStmtFromTransaction(t *testing.T) {
 	tx2.Commit()
 }
 
+func TestPreparedStmtLruFromTransaction(t *testing.T) {
+	db, _ := OpenTestConnection(&gorm.Config{PrepareStmt: true, PrepareStmtMaxSize: 10, PrepareStmtTTL: 20 * time.Second})
+
+	tx := db.Begin()
+	defer func() {
+		if r := recover(); r != nil {
+			tx.Rollback()
+		}
+	}()
+	if err := tx.Error; err != nil {
+		t.Errorf("Failed to start transaction, got error %v\n", err)
+	}
+
+	if err := tx.Where("name=?", "zzjin").Delete(&User{}).Error; err != nil {
+		tx.Rollback()
+		t.Errorf("Failed to run one transaction, got error %v\n", err)
+	}
+
+	if err := tx.Create(&User{Name: "zzjin"}).Error; err != nil {
+		tx.Rollback()
+		t.Errorf("Failed to run one transaction, got error %v\n", err)
+	}
+
+	if err := tx.Commit().Error; err != nil {
+		t.Errorf("Failed to commit transaction, got error %v\n", err)
+	}
+
+	if result := db.Where("name=?", "zzjin").Delete(&User{}); result.Error != nil || result.RowsAffected != 1 {
+		t.Fatalf("Failed, got error: %v, rows affected: %v", result.Error, result.RowsAffected)
+	}
+
+	tx2 := db.Begin()
+	if result := tx2.Where("name=?", "zzjin").Delete(&User{}); result.Error != nil || result.RowsAffected != 0 {
+		t.Fatalf("Failed, got error: %v, rows affected: %v", result.Error, result.RowsAffected)
+	}
+
+	tx2.Commit()
+	// Attempt to convert the connection pool of tx to the *gorm.PreparedStmtDB type.
+	// If the conversion is successful, ok will be true and conn will be the converted object;
+	// otherwise, ok will be false and conn will be nil.
+	conn, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
+	// Get the number of statement keys stored in the PreparedStmtDB.
+	lens := len(conn.Stmts.Keys())
+	// Check if the number of stored statement keys is 0.
+	if lens == 0 {
+		// If the number is 0, it means there are no statements stored in the LRU cache.
+		// The test fails and an error message is output.
+		t.Fatalf("lru should not be empty")
+	}
+	// Wait for 40 seconds to give the statements in the cache enough time to expire.
+	time.Sleep(time.Second * 40)
+	// Assert whether the connection pool of tx is successfully converted to the *gorm.PreparedStmtDB type.
+	AssertEqual(t, ok, true)
+	// Assert whether the number of statement keys stored in the PreparedStmtDB is 0 after 40 seconds.
+	// If it is not 0, it means the statements in the cache have not expired as expected.
+	AssertEqual(t, len(conn.Stmts.Keys()), 0)
+
+}
+
 func TestPreparedStmtDeadlock(t *testing.T) {
 	tx, err := OpenTestConnection(&gorm.Config{})
 	AssertEqual(t, err, nil)
@@ -117,9 +175,9 @@ func TestPreparedStmtDeadlock(t *testing.T) {
 
 	conn, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
 	AssertEqual(t, ok, true)
-	AssertEqual(t, len(conn.Stmts), 2)
-	for _, stmt := range conn.Stmts {
-		if stmt == nil {
+	AssertEqual(t, len(conn.Stmts.Keys()), 2)
+	for _, stmt := range conn.Stmts.Keys() {
+		if stmt == "" {
 			t.Fatalf("stmt cannot bee nil")
 		}
 	}
@@ -143,10 +201,10 @@ func TestPreparedStmtInTransaction(t *testing.T) {
 	}
 }
 
-func TestPreparedStmtReset(t *testing.T) {
+func TestPreparedStmtClose(t *testing.T) {
 	tx := DB.Session(&gorm.Session{PrepareStmt: true})
 
-	user := *GetUser("prepared_stmt_reset", Config{})
+	user := *GetUser("prepared_stmt_close", Config{})
 	tx = tx.Create(&user)
 
 	pdb, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
@@ -155,16 +213,16 @@ func TestPreparedStmtReset(t *testing.T) {
 	}
 
 	pdb.Mux.Lock()
-	if len(pdb.Stmts) == 0 {
+	if len(pdb.Stmts.Keys()) == 0 {
 		pdb.Mux.Unlock()
 		t.Fatalf("prepared stmt can not be empty")
 	}
 	pdb.Mux.Unlock()
 
-	pdb.Reset()
+	pdb.Close()
 	pdb.Mux.Lock()
 	defer pdb.Mux.Unlock()
-	if len(pdb.Stmts) != 0 {
+	if len(pdb.Stmts.Keys()) != 0 {
 		t.Fatalf("prepared stmt should be empty")
 	}
 }
@@ -174,10 +232,10 @@ func isUsingClosedConnError(err error) bool {
 	return err.Error() == "sql: statement is closed"
 }
 
-// TestPreparedStmtConcurrentReset test calling reset and executing SQL concurrently
+// TestPreparedStmtConcurrentClose test calling close and executing SQL concurrently
 // this test making sure that the gorm would not get a Segmentation Fault, and the only error cause by this is using a closed Stmt
-func TestPreparedStmtConcurrentReset(t *testing.T) {
-	name := "prepared_stmt_concurrent_reset"
+func TestPreparedStmtConcurrentClose(t *testing.T) {
+	name := "prepared_stmt_concurrent_close"
 	user := *GetUser(name, Config{})
 	createTx := DB.Session(&gorm.Session{}).Create(&user)
 	if createTx.Error != nil {
@@ -220,7 +278,7 @@ func TestPreparedStmtConcurrentReset(t *testing.T) {
 	go func() {
 		defer wg.Done()
 		<-writerFinish
-		pdb.Reset()
+		pdb.Close()
 	}()
 
 	wg.Wait()
@@ -229,88 +287,3 @@ func TestPreparedStmtConcurrentReset(t *testing.T) {
 		t.Fatalf("should is a unexpected error")
 	}
 }
-
-// TestPreparedStmtConcurrentClose test calling close and executing SQL concurrently
-// for example: one goroutine found error and just close the database, and others are executing SQL
-// this test making sure that the gorm would not get a Segmentation Fault,
-// and the only error cause by this is using a closed Stmt or gorm.ErrInvalidDB
-// and all of the goroutine must got gorm.ErrInvalidDB after database close
-func TestPreparedStmtConcurrentClose(t *testing.T) {
-	name := "prepared_stmt_concurrent_close"
-	user := *GetUser(name, Config{})
-	createTx := DB.Session(&gorm.Session{}).Create(&user)
-	if createTx.Error != nil {
-		t.Fatalf("failed to prepare record due to %s, test cannot be continue", createTx.Error)
-	}
-
-	// create a new connection to keep away from other tests
-	tx, err := OpenTestConnection(&gorm.Config{PrepareStmt: true})
-	if err != nil {
-		t.Fatalf("failed to open test connection due to %s", err)
-	}
-	pdb, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
-	if !ok {
-		t.Fatalf("should assign PreparedStatement Manager back to database when using PrepareStmt mode")
-	}
-
-	loopCount := 100
-	var wg sync.WaitGroup
-	var lastErr error
-	closeValid := make(chan struct{}, loopCount)
-	closeStartIdx := loopCount / 2 // close the database at the middle of the execution
-	var lastRunIndex int
-	var closeFinishedAt int64
-
-	wg.Add(1)
-	go func(id uint) {
-		defer wg.Done()
-		defer close(closeValid)
-		for lastRunIndex = 1; lastRunIndex <= loopCount; lastRunIndex++ {
-			if lastRunIndex == closeStartIdx {
-				closeValid <- struct{}{}
-			}
-			var tmp User
-			now := time.Now().UnixNano()
-			err := tx.Session(&gorm.Session{}).First(&tmp, id).Error
-			if err == nil {
-				closeFinishedAt := atomic.LoadInt64(&closeFinishedAt)
-				if (closeFinishedAt != 0) && (now > closeFinishedAt) {
-					lastErr = errors.New("must got error after database closed")
-					break
-				}
-				continue
-			}
-			lastErr = err
-			break
-		}
-	}(user.ID)
-
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
-		for range closeValid {
-			for i := 0; i < loopCount; i++ {
-				pdb.Close() // the Close method must can be call multiple times
-				atomic.CompareAndSwapInt64(&closeFinishedAt, 0, time.Now().UnixNano())
-			}
-		}
-	}()
-
-	wg.Wait()
-	var tmp User
-	err = tx.Session(&gorm.Session{}).First(&tmp, user.ID).Error
-	if err != gorm.ErrInvalidDB {
-		t.Fatalf("must got a gorm.ErrInvalidDB while execution after db close, got %+v instead", err)
-	}
-
-	// must be error
-	if lastErr != gorm.ErrInvalidDB && !isUsingClosedConnError(lastErr) {
-		t.Fatalf("exp error gorm.ErrInvalidDB, got %+v instead", lastErr)
-	}
-	if lastRunIndex >= loopCount || lastRunIndex < closeStartIdx {
-		t.Fatalf("exp loop times between (closeStartIdx %d <=) and (< loopCount %d), got %d instead", closeStartIdx, loopCount, lastRunIndex)
-	}
-	if pdb.Stmts != nil {
-		t.Fatalf("stmts must be nil")
-	}
-}