Return ErrBusyBuffer instead of driver.ErrBadConn

AUTHORS

@@ -12,6 +12,7 @@
 # Individual Persons
 
 Aaron Hopkins <go-sql-driver at die.net>
+Alexander Menzhinsky <amenzhinsky at gmail.com>
 Arne Hormann <arnehormann at gmail.com>
 Asta Xie <xiemengjun at gmail.com>
 Carlos Nieto <jose.carlos at menteslibres.net>

buffer.go

@@ -109,39 +109,39 @@ func (b *buffer) readNext(need int) ([]byte, error) {
 // If possible, a slice from the existing buffer is returned.
 // Otherwise a bigger buffer is made.
 // Only one buffer (total) can be used at a time.
-func (b *buffer) takeBuffer(length int) []byte {
+func (b *buffer) takeBuffer(length int) ([]byte, error) {
 	if b.length > 0 {
-		return nil
+		return nil, ErrUnreadTxRows
 	}
 
 	// test (cheap) general case first
 	if length <= defaultBufSize || length <= cap(b.buf) {
-		return b.buf[:length]
+		return b.buf[:length], nil
 	}
 
 	if length < maxPacketSize {
 		b.buf = make([]byte, length)
-		return b.buf
+		return b.buf, nil
 	}
-	return make([]byte, length)
+	return make([]byte, length), nil
 }
 
 // shortcut which can be used if the requested buffer is guaranteed to be
 // smaller than defaultBufSize
 // Only one buffer (total) can be used at a time.
-func (b *buffer) takeSmallBuffer(length int) []byte {
-	if b.length == 0 {
-		return b.buf[:length]
+func (b *buffer) takeSmallBuffer(length int) ([]byte, error) {
+	if b.length > 0 {
+		return nil, ErrUnreadTxRows
 	}
-	return nil
+	return b.buf[:length], nil
 }
 
 // takeCompleteBuffer returns the complete existing buffer.
 // This can be used if the necessary buffer size is unknown.
 // Only one buffer (total) can be used at a time.
-func (b *buffer) takeCompleteBuffer() []byte {
-	if b.length == 0 {
-		return b.buf
+func (b *buffer) takeCompleteBuffer() ([]byte, error) {
+	if b.length > 0 {
+		return nil, ErrUnreadTxRows
 	}
-	return nil
+	return b.buf, nil
 }

connection.go

@@ -141,11 +141,9 @@ func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (strin
 		return "", driver.ErrSkip
 	}
 
-	buf := mc.buf.takeCompleteBuffer()
-	if buf == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return "", driver.ErrBadConn
+	buf, err := mc.buf.takeCompleteBuffer()
+	if err != nil {
+		return "", err
 	}
 	buf = buf[:0]
 	argPos := 0

driver_test.go

@@ -1991,3 +1991,31 @@ func TestRejectReadOnly(t *testing.T) {
 		dbt.mustExec("DROP TABLE test")
 	})
 }
+
+func TestUnclosedRows(t *testing.T) {
+	runTests(t, dsn, func(dbt *DBTest) {
+		tx, err := dbt.db.Begin()
+		if err != nil {
+			dbt.Fatal(err)
+		}
+
+		rows, err := tx.Query("SELECT 1")
+		if err != nil {
+			dbt.Fatal(err)
+		}
+
+		// here's common mistake: rows are closed only
+		// when current func exits keeping the rows buffer
+		// busy for the following request.
+		defer rows.Close()
+
+		if !rows.Next() {
+			dbt.Fatal("no rows after `SELECT 1`")
+		}
+
+		_, err = tx.Query("SELECT 2")
+		if err != ErrUnreadTxRows {
+			dbt.Errorf("got %v, want %v", err, ErrUnreadTxRows)
+		}
+	})
+}

errors.go

@@ -30,7 +30,7 @@ var (
 	ErrPktSync           = errors.New("commands out of sync. You can't run this command now")
 	ErrPktSyncMul        = errors.New("commands out of sync. Did you run multiple statements at once?")
 	ErrPktTooLarge       = errors.New("packet for query is too large. Try adjusting the 'max_allowed_packet' variable on the server")
-	ErrBusyBuffer        = errors.New("busy buffer")
+	ErrUnreadTxRows      = errors.New("rows buffer is busy. Try to read out or close previous rows")
 )
 
 var errLog = Logger(log.New(os.Stderr, "[mysql] ", log.Ldate|log.Ltime|log.Lshortfile))

packets.go

@@ -259,11 +259,9 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	}
 
 	// Calculate packet length and get buffer with that size
-	data := mc.buf.takeSmallBuffer(pktLen + 4)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(pktLen + 4)
+	if err != nil {
+		return err
 	}
 
 	// ClientFlags [32 bit]
@@ -345,11 +343,9 @@ func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 
 	// Calculate the packet length and add a tailing 0
 	pktLen := len(scrambleBuff) + 1
-	data := mc.buf.takeSmallBuffer(4 + pktLen)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(4 + pktLen)
+	if err != nil {
+		return err
 	}
 
 	// Add the scrambled password [null terminated string]
@@ -364,11 +360,9 @@ func (mc *mysqlConn) writeOldAuthPacket(cipher []byte) error {
 func (mc *mysqlConn) writeClearAuthPacket() error {
 	// Calculate the packet length and add a tailing 0
 	pktLen := len(mc.cfg.Passwd) + 1
-	data := mc.buf.takeSmallBuffer(4 + pktLen)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(4 + pktLen)
+	if err != nil {
+		return err
 	}
 
 	// Add the clear password [null terminated string]
@@ -385,11 +379,9 @@ func (mc *mysqlConn) writeNativeAuthPacket(cipher []byte) error {
 
 	// Calculate the packet length and add a tailing 0
 	pktLen := len(scrambleBuff)
-	data := mc.buf.takeSmallBuffer(4 + pktLen)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(4 + pktLen)
+	if err != nil {
+		return err
 	}
 
 	// Add the scramble
@@ -406,11 +398,9 @@ func (mc *mysqlConn) writeCommandPacket(command byte) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
-	data := mc.buf.takeSmallBuffer(4 + 1)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(4 + 1)
+	if err != nil {
+		return err
 	}
 
 	// Add command byte
@@ -425,11 +415,9 @@ func (mc *mysqlConn) writeCommandPacketStr(command byte, arg string) error {
 	mc.sequence = 0
 
 	pktLen := 1 + len(arg)
-	data := mc.buf.takeBuffer(pktLen + 4)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeBuffer(pktLen + 4)
+	if err != nil {
+		return err
 	}
 
 	// Add command byte
@@ -446,11 +434,9 @@ func (mc *mysqlConn) writeCommandPacketUint32(command byte, arg uint32) error {
 	// Reset Packet Sequence
 	mc.sequence = 0
 
-	data := mc.buf.takeSmallBuffer(4 + 1 + 4)
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	data, err := mc.buf.takeSmallBuffer(4 + 1 + 4)
+	if err != nil {
+		return err
 	}
 
 	// Add command byte
@@ -907,16 +893,15 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 	mc.sequence = 0
 
 	var data []byte
+	var err error
 
 	if len(args) == 0 {
-		data = mc.buf.takeBuffer(minPktLen)
+		data, err = mc.buf.takeBuffer(minPktLen)
 	} else {
-		data = mc.buf.takeCompleteBuffer()
+		data, err = mc.buf.takeCompleteBuffer()
 	}
-	if data == nil {
-		// can not take the buffer. Something must be wrong with the connection
-		errLog.Print(ErrBusyBuffer)
-		return driver.ErrBadConn
+	if err != nil {
+		return err
 	}
 
 	// command [1 byte]