diff --git a/ssdb/app.go b/ssdb/app.go
index d3286aa..8b3e9d5 100644
--- a/ssdb/app.go
+++ b/ssdb/app.go
@@ -4,7 +4,6 @@ import (
 	"github.com/siddontang/golib/leveldb"
 	"net"
 	"strings"
-	"sync"
 )
 
 type App struct {
@@ -14,10 +13,10 @@ type App struct {
 
 	db *leveldb.DB
 
-	kvMutex   sync.Mutex
-	hashMutex sync.Mutex
-	listMutex sync.Mutex
-	zsetMutex sync.Mutex
+	kvTx   *tx
+	listTx *tx
+	hashTx *tx
+	zsetTx *tx
 }
 
 func NewApp(cfg *Config) (*App, error) {
@@ -42,6 +41,11 @@ func NewApp(cfg *Config) (*App, error) {
 		return nil, err
 	}
 
+	app.kvTx = app.newTx()
+	app.listTx = app.newTx()
+	app.hashTx = app.newTx()
+	app.zsetTx = app.newTx()
+
 	return app, nil
 }
 
diff --git a/ssdb/client.go b/ssdb/client.go
index 2c8ad96..8c7b296 100644
--- a/ssdb/client.go
+++ b/ssdb/client.go
@@ -123,8 +123,6 @@ func (c *client) readRequest() ([][]byte, error) {
 			}
 
 		} else {
-			println("return 6")
-
 			return nil, errReadRequest
 		}
 	}
diff --git a/ssdb/cmd_list.go b/ssdb/cmd_list.go
index a10cb55..4fba6e0 100644
--- a/ssdb/cmd_list.go
+++ b/ssdb/cmd_list.go
@@ -1,30 +1,131 @@
 package ssdb
 
+import (
+	"github.com/siddontang/golib/hack"
+	"strconv"
+)
+
 func lpushCommand(c *client) error {
+	args := c.args
+	if len(args) < 2 {
+		return ErrCmdParams
+	}
+
+	if n, err := c.app.list_lpush(args[0], args[1:]); err != nil {
+		return err
+	} else {
+		c.writeInteger(n)
+	}
+
 	return nil
 }
 
 func rpushCommand(c *client) error {
+	args := c.args
+	if len(args) < 2 {
+		return ErrCmdParams
+	}
+
+	if n, err := c.app.list_rpush(args[0], args[1:]); err != nil {
+		return err
+	} else {
+		c.writeInteger(n)
+	}
+
 	return nil
 }
 
 func lpopCommand(c *client) error {
+	args := c.args
+	if len(args) != 1 {
+		return ErrCmdParams
+	}
+
+	if v, err := c.app.list_lpop(args[0]); err != nil {
+		return err
+	} else {
+		c.writeBulk(v)
+	}
+
 	return nil
 }
 
 func rpopCommand(c *client) error {
+	args := c.args
+	if len(args) != 1 {
+		return ErrCmdParams
+	}
+
+	if v, err := c.app.list_rpop(args[0]); err != nil {
+		return err
+	} else {
+		c.writeBulk(v)
+	}
+
 	return nil
 }
 
 func llenCommand(c *client) error {
+	args := c.args
+	if len(args) != 1 {
+		return ErrCmdParams
+	}
+
+	if n, err := c.app.list_len(args[0]); err != nil {
+		return err
+	} else {
+		c.writeInteger(n)
+	}
+
 	return nil
 }
 
 func lindexCommand(c *client) error {
+	args := c.args
+	if len(args) != 2 {
+		return ErrCmdParams
+	}
+
+	index, err := strconv.ParseInt(hack.String(args[1]), 10, 64)
+	if err != nil {
+		return err
+	}
+
+	if v, err := c.app.list_index(args[0], index); err != nil {
+		return err
+	} else {
+		c.writeBulk(v)
+	}
+
 	return nil
 }
 
 func lrangeCommand(c *client) error {
+	args := c.args
+	if len(args) != 3 {
+		return ErrCmdParams
+	}
+
+	var start int64
+	var stop int64
+	var err error
+
+	start, err = strconv.ParseInt(hack.String(args[1]), 10, 64)
+	if err != nil {
+		return err
+	}
+
+	stop, err = strconv.ParseInt(hack.String(args[2]), 10, 64)
+	if err != nil {
+		return err
+	}
+
+	if v, err := c.app.list_range(args[0], start, stop); err != nil {
+		return err
+	} else {
+		c.writeArray(v)
+	}
+
 	return nil
 }
 
diff --git a/ssdb/cmd_list_test.go b/ssdb/cmd_list_test.go
new file mode 100644
index 0000000..8cfed80
--- /dev/null
+++ b/ssdb/cmd_list_test.go
@@ -0,0 +1,293 @@
+package ssdb
+
+import (
+	"fmt"
+	"github.com/garyburd/redigo/redis"
+	"strconv"
+	"testing"
+)
+
+func testListIndex(key []byte, index int64, v int) error {
+	c := getTestConn()
+	defer c.Close()
+
+	n, err := redis.Int(c.Do("lindex", key, index))
+	if err == redis.ErrNil && v != 0 {
+		return fmt.Errorf("must nil")
+	} else if err != nil && err != redis.ErrNil {
+		return err
+	} else if n != v {
+		return fmt.Errorf("index err number %d != %d", n, v)
+	}
+
+	return nil
+}
+
+func testListRange(key []byte, start int64, stop int64, checkValues ...int) error {
+	c := getTestConn()
+	defer c.Close()
+
+	vs, err := redis.MultiBulk(c.Do("lrange", key, start, stop))
+	if err != nil {
+		return err
+	}
+
+	if len(vs) != len(checkValues) {
+		return fmt.Errorf("invalid return number %d != %d", len(vs), len(checkValues))
+	}
+
+	var n int
+	for i, v := range vs {
+		if d, ok := v.([]byte); ok {
+			n, err = strconv.Atoi(string(d))
+			if err != nil {
+				return err
+			} else if n != checkValues[i] {
+				return fmt.Errorf("invalid data %d: %d != %d", i, n, checkValues[i])
+			}
+		} else {
+			return fmt.Errorf("invalid data %v %T", v, v)
+		}
+	}
+
+	return nil
+}
+
+func testPrintList(key []byte) {
+	headSeq, _ := testApp.db.GetString(encode_list_key(key, listHeadSeq))
+	tailSeq, _ := testApp.db.GetString(encode_list_key(key, listTailSeq))
+
+	size, _ := testApp.db.GetString(encode_lsize_key(key))
+
+	println("begin ---------------------")
+	println(headSeq, tailSeq, size)
+
+	it := testApp.db.Iterator(encode_list_key(key, listMinSeq),
+		encode_list_key(key, listMaxSeq), 0)
+	for ; it.Valid(); it.Next() {
+		k, seq, _ := decode_list_key(it.Key())
+		println(string(k), seq, string(it.Value()))
+	}
+	println("end ---------------------")
+}
+
+func TestList(t *testing.T) {
+	startTestApp()
+
+	c := getTestConn()
+	defer c.Close()
+
+	key := []byte("a")
+
+	if n, err := redis.Int(c.Do("lpush", key, 1)); err != nil {
+		t.Fatal(err)
+	} else if n != 1 {
+		t.Fatal(n)
+	}
+
+	if n, err := redis.Int(c.Do("rpush", key, 2)); err != nil {
+		t.Fatal(err)
+	} else if n != 2 {
+		t.Fatal(n)
+	}
+
+	if n, err := redis.Int(c.Do("rpush", key, 3)); err != nil {
+		t.Fatal(err)
+	} else if n != 3 {
+		t.Fatal(n)
+	}
+
+	if n, err := redis.Int(c.Do("llen", key)); err != nil {
+		t.Fatal(err)
+	} else if n != 3 {
+		t.Fatal(n)
+	}
+
+	//for redis-cli a 1 2 3
+	// 127.0.0.1:6379> lrange a 0 0
+	// 1) "1"
+	if err := testListRange(key, 0, 0, 1); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a 0 1
+	// 1) "1"
+	// 2) "2"
+
+	if err := testListRange(key, 0, 1, 1, 2); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a 0 5
+	// 1) "1"
+	// 2) "2"
+	// 3) "3"
+	if err := testListRange(key, 0, 5, 1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -1 5
+	// 1) "3"
+	if err := testListRange(key, -1, 5, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -5 -1
+	// 1) "1"
+	// 2) "2"
+	// 3) "3"
+	if err := testListRange(key, -5, -1, 1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -2 -1
+	// 1) "2"
+	// 2) "3"
+	if err := testListRange(key, -2, -1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -1 -2
+	// (empty list or set)
+	if err := testListRange(key, -1, -2); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -1 2
+	// 1) "3"
+	if err := testListRange(key, -1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -5 5
+	// 1) "1"
+	// 2) "2"
+	// 3) "3"
+	if err := testListRange(key, -5, 5, 1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -1 0
+	// (empty list or set)
+	if err := testListRange(key, -1, 0); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListRange([]byte("empty list"), 0, 100); err != nil {
+		t.Fatal(err)
+	}
+
+	// 127.0.0.1:6379> lrange a -1 -1
+	// 1) "3"
+	if err := testListRange(key, -1, -1, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, -1, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, 0, 1); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, 1, 2); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, 5, 0); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, -1, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, -2, 2); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := testListIndex(key, -3, 1); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestListMPush(t *testing.T) {
+	startTestApp()
+	c := getTestConn()
+	defer c.Close()
+
+	key := []byte("b")
+	if n, err := redis.Int(c.Do("rpush", key, 1, 2, 3)); err != nil {
+		t.Fatal(err)
+	} else if n != 3 {
+		t.Fatal(n)
+	}
+
+	if err := testListRange(key, 0, 3, 1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+
+	if n, err := redis.Int(c.Do("lpush", key, 1, 2, 3)); err != nil {
+		t.Fatal(err)
+	} else if n != 6 {
+		t.Fatal(n)
+	}
+
+	if err := testListRange(key, 0, 6, 3, 2, 1, 1, 2, 3); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPop(t *testing.T) {
+	startTestApp()
+	c := getTestConn()
+	defer c.Close()
+
+	key := []byte("c")
+	if n, err := redis.Int(c.Do("rpush", key, 1, 2, 3, 4, 5, 6)); err != nil {
+		t.Fatal(err)
+	} else if n != 6 {
+		t.Fatal(n)
+	}
+
+	if v, err := redis.Int(c.Do("lpop", key)); err != nil {
+		t.Fatal(err)
+	} else if v != 1 {
+		t.Fatal(v)
+	}
+
+	if v, err := redis.Int(c.Do("rpop", key)); err != nil {
+		t.Fatal(err)
+	} else if v != 6 {
+		t.Fatal(v)
+	}
+
+	if n, err := redis.Int(c.Do("lpush", key, 1)); err != nil {
+		t.Fatal(err)
+	} else if n != 5 {
+		t.Fatal(n)
+	}
+
+	if err := testListRange(key, 0, 5, 1, 2, 3, 4, 5); err != nil {
+		t.Fatal(err)
+	}
+
+	for i := 1; i <= 5; i++ {
+		if v, err := redis.Int(c.Do("lpop", key)); err != nil {
+			t.Fatal(err)
+		} else if v != i {
+			t.Fatal(v)
+		}
+	}
+
+	if n, err := redis.Int(c.Do("llen", key)); err != nil {
+		t.Fatal(err)
+	} else if n != 0 {
+		t.Fatal(n)
+	}
+}
diff --git a/ssdb/t_kv.go b/ssdb/t_kv.go
index b7bb4d4..fcae406 100644
--- a/ssdb/t_kv.go
+++ b/ssdb/t_kv.go
@@ -6,7 +6,6 @@ import (
 	"strconv"
 )
 
-var errEmptyKVKey = errors.New("invalid empty kv key")
 var errKVKey = errors.New("invalid encode kv key")
 
 func encode_kv_key(key []byte) []byte {
@@ -16,12 +15,12 @@ func encode_kv_key(key []byte) []byte {
 	return ek
 }
 
-func decode_kv_key(encodeKey []byte) ([]byte, error) {
-	if encodeKey[0] != KV_TYPE {
+func decode_kv_key(ek []byte) ([]byte, error) {
+	if len(ek) == 0 || ek[0] != KV_TYPE {
 		return nil, errKVKey
 	}
 
-	return encodeKey[1:], nil
+	return ek[1:], nil
 }
 
 func (a *App) kv_get(key []byte) ([]byte, error) {
@@ -34,10 +33,10 @@ func (a *App) kv_set(key []byte, value []byte) error {
 	key = encode_kv_key(key)
 	var err error
 
-	t := a.newTx()
+	t := a.kvTx
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t.Lock()
+	defer t.Unlock()
 
 	t.Put(key, value)
 
@@ -52,13 +51,13 @@ func (a *App) kv_getset(key []byte, value []byte) ([]byte, error) {
 	key = encode_kv_key(key)
 	var err error
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t := a.kvTx
+
+	t.Lock()
+	defer t.Unlock()
 
 	oldValue, _ := a.db.Get(key)
 
-	t := a.newTx()
-
 	t.Put(key, value)
 	//todo, binlog
 
@@ -73,10 +72,10 @@ func (a *App) kv_setnx(key []byte, value []byte) (int64, error) {
 
 	var n int64 = 1
 
-	t := a.newTx()
+	t := a.kvTx
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t.Lock()
+	defer t.Unlock()
 
 	if v, _ := a.db.Get(key); v != nil {
 		n = 0
@@ -108,25 +107,17 @@ func (a *App) kv_incr(key []byte, delta int64) (int64, error) {
 	key = encode_kv_key(key)
 	var err error
 
-	t := a.newTx()
+	t := a.kvTx
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t.Lock()
+	defer t.Unlock()
 
-	var v []byte
-	v, err = a.db.Get(key)
+	var n int64
+	n, err = a.db.GetInt(key)
 	if err != nil {
 		return 0, err
 	}
 
-	var n int64 = 0
-	if v != nil {
-		n, err = strconv.ParseInt(hack.String(v), 10, 64)
-		if err != nil {
-			return 0, err
-		}
-	}
-
 	n += delta
 
 	t.Put(key, hack.Slice(strconv.FormatInt(n, 10)))
@@ -142,10 +133,10 @@ func (a *App) tx_del(keys [][]byte) (int64, error) {
 		keys[i] = encode_kv_key(keys[i])
 	}
 
-	t := a.newTx()
+	t := a.kvTx
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t.Lock()
+	defer t.Unlock()
 
 	for i := range keys {
 		t.Delete(keys[i])
@@ -157,10 +148,10 @@ func (a *App) tx_del(keys [][]byte) (int64, error) {
 }
 
 func (a *App) tx_mset(args [][]byte) error {
-	t := a.newTx()
+	t := a.kvTx
 
-	a.kvMutex.Lock()
-	defer a.kvMutex.Unlock()
+	t.Lock()
+	defer t.Unlock()
 
 	for i := 0; i < len(args); i += 2 {
 		key := encode_kv_key(args[i])
diff --git a/ssdb/t_list.go b/ssdb/t_list.go
new file mode 100644
index 0000000..670f289
--- /dev/null
+++ b/ssdb/t_list.go
@@ -0,0 +1,280 @@
+package ssdb
+
+import (
+	"encoding/binary"
+	"errors"
+	"github.com/siddontang/golib/hack"
+	"strconv"
+)
+
+const (
+	listHeadSeq int64 = 1
+	listTailSeq int64 = 2
+
+	listMinSeq     int64 = 1000
+	listMaxSeq     int64 = 1<<63 - 1000
+	listInitialSeq int64 = listMinSeq + (listMaxSeq-listMinSeq)/2
+)
+
+var errLSizeKey = errors.New("invalid lsize key")
+var errListKey = errors.New("invalid list key")
+var errListSeq = errors.New("invalid list sequence, overflow")
+
+func encode_lsize_key(key []byte) []byte {
+	buf := make([]byte, len(key)+1)
+	buf[0] = LSIZE_TYPE
+
+	copy(buf[1:], key)
+	return buf
+}
+
+func decode_lsize_key(ek []byte) ([]byte, error) {
+	if len(ek) == 0 || ek[0] != LSIZE_TYPE {
+		return nil, errLSizeKey
+	}
+
+	return ek[1:], nil
+}
+
+func encode_list_key(key []byte, seq int64) []byte {
+	buf := make([]byte, len(key)+13)
+
+	pos := 0
+	buf[pos] = LIST_TYPE
+	pos++
+
+	binary.BigEndian.PutUint32(buf[pos:], uint32(len(key)))
+	pos += 4
+
+	copy(buf[pos:], key)
+	pos += len(key)
+
+	binary.BigEndian.PutUint64(buf[pos:], uint64(seq))
+
+	return buf
+}
+
+func decode_list_key(ek []byte) (key []byte, seq int64, err error) {
+	if len(ek) < 13 || ek[0] != LIST_TYPE {
+		err = errListKey
+		return
+	}
+
+	keyLen := int(binary.BigEndian.Uint32(ek[1:]))
+	if keyLen+13 != len(ek) {
+		err = errListKey
+		return
+	}
+
+	key = ek[5 : 5+keyLen]
+	seq = int64(binary.BigEndian.Uint64(ek[5+keyLen:]))
+	return
+}
+
+func (a *App) list_lpush(key []byte, args [][]byte) (int64, error) {
+	return a.list_push(key, args, listHeadSeq)
+}
+
+func (a *App) list_rpush(key []byte, args [][]byte) (int64, error) {
+	return a.list_push(key, args, listTailSeq)
+}
+
+func (a *App) list_lpop(key []byte) ([]byte, error) {
+	return a.list_pop(key, listHeadSeq)
+}
+
+func (a *App) list_rpop(key []byte) ([]byte, error) {
+	return a.list_pop(key, listTailSeq)
+}
+
+func (a *App) list_getSeq(key []byte, whereSeq int64) (int64, error) {
+	ek := encode_list_key(key, whereSeq)
+
+	return a.db.GetInt(ek)
+}
+
+func (a *App) list_len(key []byte) (int64, error) {
+	ek := encode_lsize_key(key)
+
+	return a.db.GetInt(ek)
+}
+
+func (a *App) list_push(key []byte, args [][]byte, whereSeq int64) (int64, error) {
+	t := a.listTx
+	t.Lock()
+	defer t.Unlock()
+
+	seq, err := a.list_getSeq(key, whereSeq)
+	if err != nil {
+		return 0, err
+	}
+
+	var size int64 = 0
+
+	var delta int64 = 1
+	if whereSeq == listHeadSeq {
+		delta = -1
+	}
+
+	if seq == 0 {
+		seq = listInitialSeq
+
+		t.Put(encode_list_key(key, listHeadSeq), hack.Slice(strconv.FormatInt(seq, 10)))
+		t.Put(encode_list_key(key, listTailSeq), hack.Slice(strconv.FormatInt(seq, 10)))
+	} else {
+		size, err = a.list_len(key)
+		if err != nil {
+			return 0, err
+		}
+
+		seq += delta
+	}
+
+	for i := 0; i < len(args); i++ {
+		t.Put(encode_list_key(key, seq+int64(i)*delta), args[i])
+		//to do add binlog
+	}
+
+	seq += int64(len(args)-1) * delta
+
+	if seq <= listMinSeq || seq >= listMaxSeq {
+		return 0, errListSeq
+	}
+
+	size += int64(len(args))
+
+	t.Put(encode_lsize_key(key), hack.Slice(strconv.FormatInt(size, 10)))
+	t.Put(encode_list_key(key, whereSeq), hack.Slice(strconv.FormatInt(seq, 10)))
+
+	err = t.Commit()
+
+	return size, err
+}
+
+func (a *App) list_pop(key []byte, whereSeq int64) ([]byte, error) {
+	t := a.listTx
+	t.Lock()
+	defer t.Unlock()
+
+	var delta int64 = 1
+	if whereSeq == listTailSeq {
+		delta = -1
+	}
+
+	seq, err := a.list_getSeq(key, whereSeq)
+	if err != nil {
+		return nil, err
+	}
+
+	var value []byte
+	value, err = a.db.Get(encode_list_key(key, seq))
+	if err != nil {
+		return nil, err
+	}
+
+	t.Delete(encode_list_key(key, seq))
+	seq += delta
+
+	var size int64
+	size, err = a.list_len(key)
+	if err != nil {
+		return nil, err
+	}
+
+	size--
+	if size <= 0 {
+		t.Delete(encode_lsize_key(key))
+		t.Delete(encode_list_key(key, listHeadSeq))
+		t.Delete(encode_list_key(key, listTailSeq))
+	} else {
+		t.Put(encode_list_key(key, whereSeq), hack.Slice(strconv.FormatInt(seq, 10)))
+		t.Put(encode_lsize_key(key), hack.Slice(strconv.FormatInt(size, 10)))
+	}
+
+	//todo add binlog
+	err = t.Commit()
+	return value, err
+}
+
+func (a *App) list_range(key []byte, start int64, stop int64) ([]interface{}, error) {
+	v := make([]interface{}, 0, 16)
+
+	var startSeq int64
+	var stopSeq int64
+
+	if start > stop {
+		return []interface{}{}, nil
+	} else if start >= 0 && stop >= 0 {
+		seq, err := a.list_getSeq(key, listHeadSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		startSeq = seq + start
+		stopSeq = seq + stop + 1
+
+	} else if start < 0 && stop < 0 {
+		seq, err := a.list_getSeq(key, listTailSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		startSeq = seq + start + 1
+		stopSeq = seq + stop + 2
+	} else {
+		//start < 0 && stop > 0
+		var err error
+		startSeq, err = a.list_getSeq(key, listTailSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		startSeq += start + 1
+
+		stopSeq, err = a.list_getSeq(key, listHeadSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		stopSeq += stop + 1
+	}
+
+	if startSeq < listMinSeq {
+		startSeq = listMinSeq
+	} else if stopSeq > listMaxSeq {
+		stopSeq = listMaxSeq
+	}
+
+	it := a.db.Iterator(encode_list_key(key, startSeq),
+		encode_list_key(key, stopSeq), 0)
+	for ; it.Valid(); it.Next() {
+		v = append(v, it.Value())
+	}
+
+	it.Close()
+
+	return v, nil
+}
+
+func (a *App) list_index(key []byte, index int64) ([]byte, error) {
+	var seq int64
+	var err error
+	if index >= 0 {
+		seq, err = a.list_getSeq(key, listHeadSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		seq = seq + index
+
+	} else {
+		seq, err = a.list_getSeq(key, listTailSeq)
+		if err != nil {
+			return nil, err
+		}
+
+		seq = seq + index + 1
+	}
+
+	return a.db.Get(encode_list_key(key, seq))
+}
diff --git a/ssdb/tx.go b/ssdb/tx.go
index 2f34525..afe7d40 100644
--- a/ssdb/tx.go
+++ b/ssdb/tx.go
@@ -2,9 +2,12 @@ package ssdb
 
 import (
 	"github.com/siddontang/golib/leveldb"
+	"sync"
 )
 
 type tx struct {
+	m sync.Mutex
+
 	app *App
 
 	wb *leveldb.WriteBatch
@@ -20,6 +23,10 @@ func (app *App) newTx() *tx {
 	return t
 }
 
+func (t *tx) Close() {
+	t.wb.Close()
+}
+
 func (t *tx) Put(key []byte, value []byte) {
 	t.wb.Put(key, value)
 }
@@ -28,6 +35,15 @@ func (t *tx) Delete(key []byte) {
 	t.wb.Delete(key)
 }
 
+func (t *tx) Lock() {
+	t.m.Lock()
+}
+
+func (t *tx) Unlock() {
+	t.wb.Rollback()
+	t.m.Unlock()
+}
+
 func (t *tx) Commit() error {
 	err := t.wb.Commit()
 	return err