Another step toward Stmt cache support.

cache.go

@@ -49,11 +49,10 @@ func (c *Cache) find(sql string) *Stmt {
 	return nil
 }
 
-// TODO To be called instead of Stmt#Finalize
-func (c *Cache) release(s *Stmt) {
+// To be called in Stmt#Finalize
+func (c *Cache) release(s *Stmt) error {
 	if c.maxSize <= 0 || len(s.tail) > 0 {
-		s.Finalize()
-		return
+		return s.finalize()
 	}
 	c.m.Lock()
 	defer c.m.Unlock()
@@ -61,9 +60,10 @@ func (c *Cache) release(s *Stmt) {
 	for c.l.Len() > c.maxSize {
 		v := c.l.Remove(c.l.Back())
 		if s, ok := v.(*Stmt); ok {
-			s.Finalize()
+			s.finalize()
 		}
 	}
+	return nil
 }
 
 // Finalize and free the cached prepared statements
@@ -79,7 +79,7 @@ func (c *Cache) flush() {
 		next = e.Next()
 		v := c.l.Remove(e)
 		if s, ok := v.(*Stmt); ok {
-			s.Finalize()
+			s.finalize()
 		} else {
 			panic(fmt.Sprintf("unexpected element in Stmt cache: %#v", v))
 		}

meta.go

@@ -40,7 +40,7 @@ func (c *Conn) Databases() (map[string]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var databases map[string]string = make(map[string]string)
 	var name, file string
 	err = s.Select(func(s *Stmt) (err error) {
@@ -63,7 +63,7 @@ func (c *Conn) Tables() ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var tables []string = make([]string, 0, 20)
 	err = s.Select(func(s *Stmt) (err error) {
 		name, _ := s.ScanText(0)
@@ -95,7 +95,7 @@ func (c *Conn) Columns(table string) ([]Column, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var columns []Column = make([]Column, 0, 20)
 	err = s.Select(func(s *Stmt) (err error) {
 		c := Column{}
@@ -148,7 +148,7 @@ func (c *Conn) ForeignKeys(table string) (map[int]*ForeignKey, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var fks = make(map[int]*ForeignKey)
 	var id, seq int
 	var ref, from, to string
@@ -185,7 +185,7 @@ func (c *Conn) Indexes(table string) ([]Index, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var indexes []Index = make([]Index, 0, 5)
 	err = s.Select(func(s *Stmt) (err error) {
 		i := Index{}
@@ -208,7 +208,7 @@ func (c *Conn) IndexColumns(index string) ([]Column, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	var columns []Column = make([]Column, 0, 5)
 	err = s.Select(func(s *Stmt) (err error) {
 		c := Column{}

sqlite.go

@@ -319,24 +319,24 @@ func (c *Conn) Exec(cmd string, args ...interface{}) error {
 		} else if s.stmt == nil {
 			// this happens for a comment or white-space
 			cmd = s.tail
-			if err = s.Finalize(); err != nil {
+			if err = s.finalize(); err != nil {
 				return err
 			}
 			continue
 		}
 		err = s.Exec(args...)
 		if err != nil {
-			s.Finalize()
+			s.finalize()
 			return err
 		}
 		if len(s.tail) > 0 {
 			if len(args) > 0 {
-				s.Finalize()
+				s.finalize()
 				return c.specificError("Cannot execute multiple statements when args are specified")
 			}
 		}
 		cmd = s.tail
-		if err = s.Finalize(); err != nil {
+		if err = s.finalize(); err != nil {
 			return err
 		}
 	}
@@ -349,7 +349,7 @@ func (c *Conn) Exists(query string, args ...interface{}) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	return s.Next()
 }
 
@@ -360,7 +360,7 @@ func (c *Conn) OneValue(query string, value interface{}, args ...interface{}) er
 	if err != nil {
 		return err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	b, err := s.Next()
 	if err != nil {
 		return err
@@ -445,7 +445,7 @@ func (c *Conn) exec(cmd string) error {
 	if err != nil {
 		return err
 	}
-	defer s.Finalize()
+	defer s.finalize()
 	rv := C.sqlite3_step(s.stmt)
 	if Errno(rv) != Done {
 		return s.error(rv)

stmt.go

@@ -76,8 +76,10 @@ type Stmt struct {
 	cols               map[string]int // cached columns index by name
 	bindParameterCount int
 	params             map[string]int // cached parameter index by name
-	// Enable type check in Scan methods
+	// Enable type check in Scan methods (default true)
 	CheckTypeMismatch bool
+	// Tell if the stmt should be cached (default false)
+	Cacheable bool
 }
 
 // Compile an SQL statement and optionally bind values.
@@ -109,7 +111,7 @@ func (c *Conn) Prepare(cmd string, args ...interface{}) (*Stmt, error) {
 	if len(args) > 0 {
 		err := s.Bind(args...)
 		if err != nil {
-			s.Finalize()
+			s.finalize()
 			return nil, err
 		}
 	}
@@ -880,6 +882,12 @@ func (s *Stmt) Busy() bool {
 // Destroy a prepared statement
 // (See http://sqlite.org/c3ref/finalize.html)
 func (s *Stmt) Finalize() error {
+	if s.Cacheable {
+		return s.c.stmtCache.release(s)
+	}
+	return s.finalize()
+}
+func (s *Stmt) finalize() error {
 	rv := C.sqlite3_finalize(s.stmt)
 	if rv != C.SQLITE_OK {
 		return s.error(rv)