sql: add DB.Close, fix bugs, remove Execer on Driver (only Conn)

R=rsc
CC=golang-dev
https://golang.org/cl/5372099

src/pkg/exp/sql/sql.go

@@ -88,8 +88,9 @@ type DB struct {
 	driver driver.Driver
 	dsn    string
 
-	mu       sync.Mutex
+	mu       sync.Mutex // protects freeConn and closed
 	freeConn []driver.Conn
+	closed   bool
 }
 
 // Open opens a database specified by its database driver name and a
@@ -106,6 +107,22 @@ func Open(driverName, dataSourceName string) (*DB, error) {
 	return &DB{driver: driver, dsn: dataSourceName}, nil
 }
 
+// Close closes the database, releasing any open resources.
+func (db *DB) Close() error {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	var err error
+	for _, c := range db.freeConn {
+		err1 := c.Close()
+		if err1 != nil {
+			err = err1
+		}
+	}
+	db.freeConn = nil
+	db.closed = true
+	return err
+}
+
 func (db *DB) maxIdleConns() int {
 	const defaultMaxIdleConns = 2
 	// TODO(bradfitz): ask driver, if supported, for its default preference
@@ -116,6 +133,9 @@ func (db *DB) maxIdleConns() int {
 // conn returns a newly-opened or cached driver.Conn
 func (db *DB) conn() (driver.Conn, error) {
 	db.mu.Lock()
+	if db.closed {
+		return nil, errors.New("sql: database is closed")
+	}
 	if n := len(db.freeConn); n > 0 {
 		conn := db.freeConn[n-1]
 		db.freeConn = db.freeConn[:n-1]
@@ -140,11 +160,13 @@ func (db *DB) connIfFree(wanted driver.Conn) (conn driver.Conn, ok bool) {
 }
 
 func (db *DB) putConn(c driver.Conn) {
-	if n := len(db.freeConn); n < db.maxIdleConns() {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+	if n := len(db.freeConn); !db.closed && n < db.maxIdleConns() {
 		db.freeConn = append(db.freeConn, c)
 		return
 	}
-	db.closeConn(c)
+	db.closeConn(c) // TODO(bradfitz): release lock before calling this?
 }
 
 func (db *DB) closeConn(c driver.Conn) {
@@ -180,17 +202,11 @@ func (db *DB) Prepare(query string) (*Stmt, error) {
 
 // Exec executes a query without returning any rows.
 func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
-	// Optional fast path, if the driver implements driver.Execer.
-	if execer, ok := db.driver.(driver.Execer); ok {
-		resi, err := execer.Exec(query, args)
-		if err != nil {
-			return nil, err
-		}
-		return result{resi}, nil
+	sargs, err := subsetTypeArgs(args)
+	if err != nil {
+		return nil, err
 	}
 
-	// If the driver does not implement driver.Execer, we need
-	// a connection.
 	ci, err := db.conn()
 	if err != nil {
 		return nil, err
@@ -198,11 +214,13 @@ func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
 	defer db.putConn(ci)
 
 	if execer, ok := ci.(driver.Execer); ok {
-		resi, err := execer.Exec(query, args)
-		if err != nil {
-			return nil, err
+		resi, err := execer.Exec(query, sargs)
+		if err != driver.ErrSkip {
+			if err != nil {
+				return nil, err
+			}
+			return result{resi}, nil
 		}
-		return result{resi}, nil
 	}
 
 	sti, err := ci.Prepare(query)
@@ -210,7 +228,8 @@ func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
 		return nil, err
 	}
 	defer sti.Close()
-	resi, err := sti.Exec(args)
+
+	resi, err := sti.Exec(sargs)
 	if err != nil {
 		return nil, err
 	}
@@ -386,7 +405,13 @@ func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
 		return nil, err
 	}
 	defer sti.Close()
-	resi, err := sti.Exec(args)
+
+	sargs, err := subsetTypeArgs(args)
+	if err != nil {
+		return nil, err
+	}
+
+	resi, err := sti.Exec(sargs)
 	if err != nil {
 		return nil, err
 	}
@@ -548,7 +573,11 @@ func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
 	if len(args) != si.NumInput() {
 		return nil, fmt.Errorf("db: statement expects %d inputs; got %d", si.NumInput(), len(args))
 	}
-	rowsi, err := si.Query(args)
+	sargs, err := subsetTypeArgs(args)
+	if err != nil {
+		return nil, err
+	}
+	rowsi, err := si.Query(sargs)
 	if err != nil {
 		s.db.putConn(ci)
 		return nil, err