diff --git a/build_leveldb.sh b/build_leveldb.sh
index 1940e9a..df918d5 100644
--- a/build_leveldb.sh
+++ b/build_leveldb.sh
@@ -42,4 +42,4 @@ else
     echo "skip install leveldb"
 fi
 
-cd $ROOT_DIR
\ No newline at end of file
+cd $ROOT_DIR
diff --git a/dev.sh b/dev.sh
index 3fee497..c1c59f7 100644
--- a/dev.sh
+++ b/dev.sh
@@ -31,6 +31,11 @@ export GOPATH=$(add_path $GOPATH $VTROOT)
 export CGO_CFLAGS="-I$LEVELDB_DIR/include -I$SNAPPY_DIR/include"
 export CGO_CXXFLAGS="-I$LEVELDB_DIR/include -I$SNAPPY_DIR/include"
 export CGO_LDFLAGS="-L$LEVELDB_DIR/lib -L$SNAPPY_DIR/lib -lsnappy"
+
+#for linux, use LD_LIBRARY_PATH
 export LD_LIBRARY_PATH=$(add_path $LD_LIBRARY_PATH $SNAPPY_DIR/lib)
 export LD_LIBRARY_PATH=$(add_path $LD_LIBRARY_PATH $LEVELDB_DIR/lib)
 
+#for macos, use DYLD_LIBRARY_PATH
+export DYLD_LIBRARY_PATH=$(add_path $DYLD_LIBRARY_PATH $SNAPPY_DIR/lib)
+export DYLD_LIBRARY_PATH=$(add_path $DYLD_LIBRARY_PATH $LEVELDB_DIR/lib)
diff --git a/ledis/app.go b/ledis/app.go
index a0a6757..5cbdacd 100644
--- a/ledis/app.go
+++ b/ledis/app.go
@@ -1,7 +1,6 @@
 package ledis
 
 import (
-	"github.com/siddontang/go-leveldb/leveldb"
 	"net"
 	"strings"
 )
@@ -11,12 +10,7 @@ type App struct {
 
 	listener net.Listener
 
-	db *leveldb.DB
-
-	kvTx   *tx
-	listTx *tx
-	hashTx *tx
-	zsetTx *tx
+	db *DB
 
 	closed bool
 }
@@ -40,16 +34,11 @@ func NewApp(cfg *Config) (*App, error) {
 		return nil, err
 	}
 
-	app.db, err = leveldb.OpenWithConfig(&cfg.DB)
+	app.db, err = OpenDBWithConfig(&cfg.DB)
 	if err != nil {
 		return nil, err
 	}
 
-	app.kvTx = app.newTx()
-	app.listTx = app.newTx()
-	app.hashTx = app.newTx()
-	app.zsetTx = app.newTx()
-
 	return app, nil
 }
 
@@ -72,6 +61,6 @@ func (app *App) Run() {
 			continue
 		}
 
-		newClient(conn, app)
+		newClient(conn, app.db)
 	}
 }
diff --git a/ledis/client.go b/ledis/client.go
index c71d16a..2a57c53 100644
--- a/ledis/client.go
+++ b/ledis/client.go
@@ -14,8 +14,8 @@ import (
 var errReadRequest = errors.New("invalid request protocol")
 
 type client struct {
-	app *App
-	c   net.Conn
+	db *DB
+	c  net.Conn
 
 	rb *bufio.Reader
 	wb *bufio.Writer
@@ -26,9 +26,9 @@ type client struct {
 	reqC chan error
 }
 
-func newClient(c net.Conn, app *App) {
+func newClient(c net.Conn, db *DB) {
 	co := new(client)
-	co.app = app
+	co.db = db
 	co.c = c
 
 	co.rb = bufio.NewReaderSize(c, 256)
diff --git a/ledis/cmd_hash.go b/ledis/cmd_hash.go
index 86b424f..1e00854 100644
--- a/ledis/cmd_hash.go
+++ b/ledis/cmd_hash.go
@@ -8,7 +8,7 @@ func hsetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.hash_set(args[0], args[1], args[2]); err != nil {
+	if n, err := c.db.HSet(args[0], args[1], args[2]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -23,7 +23,7 @@ func hgetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.hash_get(args[0], args[1]); err != nil {
+	if v, err := c.db.HGet(args[0], args[1]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -39,7 +39,7 @@ func hexistsCommand(c *client) error {
 	}
 
 	var n int64 = 1
-	if v, err := c.app.hash_get(args[0], args[1]); err != nil {
+	if v, err := c.db.HGet(args[0], args[1]); err != nil {
 		return err
 	} else {
 		if v == nil {
@@ -57,7 +57,7 @@ func hdelCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.hash_del(args[0], args[1:]); err != nil {
+	if n, err := c.db.HDel(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -72,7 +72,7 @@ func hlenCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.hash_len(args[0]); err != nil {
+	if n, err := c.db.HLen(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -93,7 +93,7 @@ func hincrbyCommand(c *client) error {
 	}
 
 	var n int64
-	if n, err = c.app.hash_incrby(args[0], args[1], delta); err != nil {
+	if n, err = c.db.HIncrBy(args[0], args[1], delta); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -111,7 +111,7 @@ func hmsetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if err := c.app.hash_mset(args[0], args[1:]); err != nil {
+	if err := c.db.HMset(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeStatus(OK)
@@ -126,7 +126,7 @@ func hmgetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.hash_mget(args[0], args[1:]); err != nil {
+	if v, err := c.db.HMget(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -141,7 +141,7 @@ func hgetallCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.hash_getall(args[0]); err != nil {
+	if v, err := c.db.HGetAll(args[0]); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -156,7 +156,7 @@ func hkeysCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.hash_keys(args[0]); err != nil {
+	if v, err := c.db.HKeys(args[0]); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -171,7 +171,7 @@ func hvalsCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.hash_values(args[0]); err != nil {
+	if v, err := c.db.HValues(args[0]); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -186,7 +186,7 @@ func hclearCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.hash_clear(args[0]); err != nil {
+	if n, err := c.db.HClear(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
diff --git a/ledis/cmd_kv.go b/ledis/cmd_kv.go
index 381ec8c..754fb95 100644
--- a/ledis/cmd_kv.go
+++ b/ledis/cmd_kv.go
@@ -8,7 +8,7 @@ func getCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.kv_get(args[0]); err != nil {
+	if v, err := c.db.Get(args[0]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -22,7 +22,7 @@ func setCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if err := c.app.kv_set(args[0], args[1]); err != nil {
+	if err := c.db.Set(args[0], args[1]); err != nil {
 		return err
 	} else {
 		c.writeStatus(OK)
@@ -37,7 +37,7 @@ func getsetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.kv_getset(args[0], args[1]); err != nil {
+	if v, err := c.db.GetSet(args[0], args[1]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -52,7 +52,7 @@ func setnxCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.kv_setnx(args[0], args[1]); err != nil {
+	if n, err := c.db.SetNX(args[0], args[1]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -67,7 +67,7 @@ func existsCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.kv_exists(args[0]); err != nil {
+	if n, err := c.db.Exists(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -82,7 +82,7 @@ func incrCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.kv_incr(c.args[0], 1); err != nil {
+	if n, err := c.db.Incr(c.args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -97,7 +97,7 @@ func decrCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.kv_incr(c.args[0], -1); err != nil {
+	if n, err := c.db.Decr(c.args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -117,7 +117,7 @@ func incrbyCommand(c *client) error {
 		return err
 	}
 
-	if n, err := c.app.kv_incr(c.args[0], delta); err != nil {
+	if n, err := c.db.IncryBy(c.args[0], delta); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -137,7 +137,7 @@ func decrbyCommand(c *client) error {
 		return err
 	}
 
-	if n, err := c.app.kv_incr(c.args[0], -delta); err != nil {
+	if n, err := c.db.DecrBy(c.args[0], -delta); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -152,7 +152,7 @@ func delCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.tx_del(args); err != nil {
+	if n, err := c.db.Del(args); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -167,7 +167,7 @@ func msetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if err := c.app.tx_mset(args); err != nil {
+	if err := c.db.MSet(args); err != nil {
 		return err
 	} else {
 		c.writeStatus(OK)
@@ -186,7 +186,7 @@ func mgetCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.kv_mget(args); err != nil {
+	if v, err := c.db.MGet(args); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -207,6 +207,5 @@ func init() {
 	register("mget", mgetCommand)
 	register("mset", msetCommand)
 	register("set", setCommand)
-	//	register("setex", setexCommand)
 	register("setnx", setnxCommand)
 }
diff --git a/ledis/cmd_list.go b/ledis/cmd_list.go
index e41f520..213d432 100644
--- a/ledis/cmd_list.go
+++ b/ledis/cmd_list.go
@@ -8,7 +8,7 @@ func lpushCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.list_lpush(args[0], args[1:]); err != nil {
+	if n, err := c.db.LPush(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -23,7 +23,7 @@ func rpushCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.list_rpush(args[0], args[1:]); err != nil {
+	if n, err := c.db.RPush(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -38,7 +38,7 @@ func lpopCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.list_lpop(args[0]); err != nil {
+	if v, err := c.db.LPop(args[0]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -53,7 +53,7 @@ func rpopCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.list_rpop(args[0]); err != nil {
+	if v, err := c.db.RPop(args[0]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -68,7 +68,7 @@ func llenCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.list_len(args[0]); err != nil {
+	if n, err := c.db.LLen(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -88,7 +88,7 @@ func lindexCommand(c *client) error {
 		return err
 	}
 
-	if v, err := c.app.list_index(args[0], int32(index)); err != nil {
+	if v, err := c.db.LIndex(args[0], int32(index)); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -117,7 +117,7 @@ func lrangeCommand(c *client) error {
 		return err
 	}
 
-	if v, err := c.app.list_range(args[0], int32(start), int32(stop)); err != nil {
+	if v, err := c.db.LRange(args[0], int32(start), int32(stop)); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -132,7 +132,7 @@ func lclearCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.list_clear(args[0]); err != nil {
+	if n, err := c.db.LClear(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
diff --git a/ledis/cmd_list_test.go b/ledis/cmd_list_test.go
index 33b7455..7670a4a 100644
--- a/ledis/cmd_list_test.go
+++ b/ledis/cmd_list_test.go
@@ -53,16 +53,6 @@ func testListRange(key []byte, start int64, stop int64, checkValues ...int) erro
 	return nil
 }
 
-func testPrintList(key []byte) {
-	it := testApp.db.Iterator(encode_list_key(key, listMinSeq),
-		encode_list_key(key, listMaxSeq), 0, 0, -1)
-	for ; it.Valid(); it.Next() {
-		k, seq, _ := decode_list_key(it.Key())
-		println(string(k), "seq ", seq, "value:", string(it.Value()))
-	}
-	println("end ---------------------")
-}
-
 func TestList(t *testing.T) {
 	startTestApp()
 
diff --git a/ledis/cmd_zset.go b/ledis/cmd_zset.go
index 4f84e24..9e21be1 100644
--- a/ledis/cmd_zset.go
+++ b/ledis/cmd_zset.go
@@ -9,11 +9,6 @@ import (
 
 //for simple implementation, we only support int64 score
 
-const (
-	MinScore int64 = -1<<63 + 1
-	MaxScore int64 = 1<<63 - 1
-)
-
 var errScoreOverflow = errors.New("zset score overflow")
 
 func zaddCommand(c *client) error {
@@ -39,7 +34,7 @@ func zaddCommand(c *client) error {
 		params[i+1] = args[i+1]
 	}
 
-	if n, err := c.app.zset_add(key, params); err != nil {
+	if n, err := c.db.ZAdd(key, params); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -54,7 +49,7 @@ func zcardCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.zset_card(args[0]); err != nil {
+	if n, err := c.db.ZCard(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -69,7 +64,7 @@ func zscoreCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if v, err := c.app.zset_score(args[0], args[1]); err != nil {
+	if v, err := c.db.ZScore(args[0], args[1]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -84,7 +79,7 @@ func zremCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.zset_rem(args[0], args[1:]); err != nil {
+	if n, err := c.db.ZRem(args[0], args[1:]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -106,7 +101,7 @@ func zincrbyCommand(c *client) error {
 		return err
 	}
 
-	if v, err := c.app.zset_incrby(key, delta, args[2]); err != nil {
+	if v, err := c.db.ZIncrBy(key, delta, args[2]); err != nil {
 		return err
 	} else {
 		c.writeBulk(v)
@@ -193,7 +188,7 @@ func zcountCommand(c *client) error {
 		return nil
 	}
 
-	if n, err := c.app.zset_count(args[0], min, max); err != nil {
+	if n, err := c.db.ZCount(args[0], min, max); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -208,7 +203,7 @@ func zrankCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.zset_rank(args[0], args[1], false); err != nil {
+	if n, err := c.db.ZRank(args[0], args[1]); err != nil {
 		return err
 	} else if n == -1 {
 		c.writeBulk(nil)
@@ -225,7 +220,7 @@ func zrevrankCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.zset_rank(args[0], args[1], true); err != nil {
+	if n, err := c.db.ZRevRank(args[0], args[1]); err != nil {
 		return err
 	} else if n == -1 {
 		c.writeBulk(nil)
@@ -244,17 +239,12 @@ func zremrangebyrankCommand(c *client) error {
 
 	key := args[0]
 
-	offset, limit, err := zparseRange(c, key, args[1], args[2])
+	start, stop, err := zparseRange(c, args[1], args[2])
 	if err != nil {
 		return err
 	}
 
-	if offset < 0 {
-		c.writeInteger(0)
-		return nil
-	}
-
-	if n, err := c.app.zset_remRange(key, MinScore, MaxScore, offset, limit); err != nil {
+	if n, err := c.db.ZRemRangeByRank(key, start, stop); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -275,7 +265,7 @@ func zremrangebyscoreCommand(c *client) error {
 		return err
 	}
 
-	if n, err := c.app.zset_remRange(key, min, max, 0, -1); err != nil {
+	if n, err := c.db.ZRemRangeByScore(key, min, max); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
@@ -284,51 +274,15 @@ func zremrangebyscoreCommand(c *client) error {
 	return nil
 }
 
-func zparseRange(c *client, key []byte, startBuf []byte, stopBuf []byte) (offset int, limit int, err error) {
-	var start int
-	var stop int
-	if start, err = strconv.Atoi(String(startBuf)); err != nil {
+func zparseRange(c *client, a1 []byte, a2 []byte) (start int, stop int, err error) {
+	if start, err = strconv.Atoi(String(a1)); err != nil {
 		return
 	}
 
-	if stop, err = strconv.Atoi(String(stopBuf)); err != nil {
+	if stop, err = strconv.Atoi(String(a2)); err != nil {
 		return
 	}
 
-	if start < 0 || stop < 0 {
-		//refer redis implementation
-		var size int64
-		size, err = c.app.zset_card(key)
-		if err != nil {
-			return
-		}
-
-		llen := int(size)
-
-		if start < 0 {
-			start = llen + start
-		}
-		if stop < 0 {
-			stop = llen + stop
-		}
-
-		if start < 0 {
-			start = 0
-		}
-
-		if start >= llen {
-			offset = -1
-			return
-		}
-	}
-
-	if start > stop {
-		offset = -1
-		return
-	}
-
-	offset = start
-	limit = (stop - start) + 1
 	return
 }
 
@@ -340,16 +294,11 @@ func zrangeGeneric(c *client, reverse bool) error {
 
 	key := args[0]
 
-	offset, limit, err := zparseRange(c, key, args[1], args[2])
+	start, stop, err := zparseRange(c, args[1], args[2])
 	if err != nil {
 		return err
 	}
 
-	if offset < 0 {
-		c.writeArray([]interface{}{})
-		return nil
-	}
-
 	args = args[3:]
 	var withScores bool = false
 
@@ -357,7 +306,7 @@ func zrangeGeneric(c *client, reverse bool) error {
 		withScores = true
 	}
 
-	if v, err := c.app.zset_range(key, MinScore, MaxScore, withScores, offset, limit, reverse); err != nil {
+	if v, err := c.db.ZRangeGeneric(key, start, stop, withScores, reverse); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -395,7 +344,7 @@ func zrangebyscoreGeneric(c *client, reverse bool) error {
 	}
 
 	var offset int = 0
-	var limit int = -1
+	var count int = -1
 
 	if len(args) > 0 {
 		if len(args) != 3 {
@@ -410,7 +359,7 @@ func zrangebyscoreGeneric(c *client, reverse bool) error {
 			return ErrCmdParams
 		}
 
-		if limit, err = strconv.Atoi(String(args[2])); err != nil {
+		if count, err = strconv.Atoi(String(args[2])); err != nil {
 			return ErrCmdParams
 		}
 	}
@@ -422,7 +371,7 @@ func zrangebyscoreGeneric(c *client, reverse bool) error {
 		return nil
 	}
 
-	if v, err := c.app.zset_range(key, min, max, withScores, offset, limit, reverse); err != nil {
+	if v, err := c.db.ZRangeByScoreGeneric(key, min, max, withScores, offset, count, reverse); err != nil {
 		return err
 	} else {
 		c.writeArray(v)
@@ -445,7 +394,7 @@ func zclearCommand(c *client) error {
 		return ErrCmdParams
 	}
 
-	if n, err := c.app.zset_clear(args[0]); err != nil {
+	if n, err := c.db.ZClear(args[0]); err != nil {
 		return err
 	} else {
 		c.writeInteger(n)
diff --git a/ledis/db.go b/ledis/db.go
new file mode 100644
index 0000000..4973722
--- /dev/null
+++ b/ledis/db.go
@@ -0,0 +1,50 @@
+package ledis
+
+import (
+	"encoding/json"
+	"github.com/siddontang/go-leveldb/leveldb"
+)
+
+type DB struct {
+	db *leveldb.DB
+
+	kvTx   *tx
+	listTx *tx
+	hashTx *tx
+	zsetTx *tx
+}
+
+func OpenDB(configJson json.RawMessage) (*DB, error) {
+	db, err := leveldb.Open(configJson)
+	if err != nil {
+		return nil, err
+	}
+
+	return newDB(db)
+}
+
+func OpenDBWithConfig(cfg *leveldb.Config) (*DB, error) {
+	db, err := leveldb.OpenWithConfig(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return newDB(db)
+}
+
+func newDB(db *leveldb.DB) (*DB, error) {
+	d := new(DB)
+
+	d.db = db
+
+	d.kvTx = &tx{wb: db.NewWriteBatch()}
+	d.listTx = &tx{wb: db.NewWriteBatch()}
+	d.hashTx = &tx{wb: db.NewWriteBatch()}
+	d.zsetTx = &tx{wb: db.NewWriteBatch()}
+
+	return d, nil
+}
+
+func (db *DB) Close() {
+	db.db.Close()
+}
diff --git a/ledis/lock.go b/ledis/lock.go
deleted file mode 100644
index 8dfd4cd..0000000
--- a/ledis/lock.go
+++ /dev/null
@@ -1,27 +0,0 @@
-package ledis
-
-import (
-	"hash/crc32"
-	"sync"
-)
-
-type keyMutex struct {
-	mutexs []*sync.Mutex
-}
-
-func newKeyMutex(size int) *keyMutex {
-	m := new(keyMutex)
-
-	m.mutexs = make([]*sync.Mutex, size)
-
-	for i := range m.mutexs {
-		m.mutexs[i] = &sync.Mutex{}
-	}
-
-	return m
-}
-
-func (k *keyMutex) Get(key []byte) *sync.Mutex {
-	h := int(crc32.ChecksumIEEE(key))
-	return k.mutexs[h%len(k.mutexs)]
-}
diff --git a/ledis/t_hash.go b/ledis/t_hash.go
index 55a2568..daedfc2 100644
--- a/ledis/t_hash.go
+++ b/ledis/t_hash.go
@@ -87,20 +87,20 @@ func decode_hash_key(ek []byte) ([]byte, []byte, error) {
 	return key, field, nil
 }
 
-func (a *App) hash_len(key []byte) (int64, error) {
-	return Int64(a.db.Get(encode_hsize_key(key)))
+func (db *DB) HLen(key []byte) (int64, error) {
+	return Int64(db.db.Get(encode_hsize_key(key)))
 }
 
-func (a *App) hash_setItem(key []byte, field []byte, value []byte) (int64, error) {
-	t := a.hashTx
+func (db *DB) hSetItem(key []byte, field []byte, value []byte) (int64, error) {
+	t := db.hashTx
 
 	ek := encode_hash_key(key, field)
 
 	var n int64 = 1
-	if v, _ := a.db.Get(ek); v != nil {
+	if v, _ := db.db.Get(ek); v != nil {
 		n = 0
 	} else {
-		if _, err := a.hash_incrSize(key, 1); err != nil {
+		if _, err := db.hIncrSize(key, 1); err != nil {
 			return 0, err
 		}
 	}
@@ -109,12 +109,12 @@ func (a *App) hash_setItem(key []byte, field []byte, value []byte) (int64, error
 	return n, nil
 }
 
-func (a *App) hash_set(key []byte, field []byte, value []byte) (int64, error) {
-	t := a.hashTx
+func (db *DB) HSet(key []byte, field []byte, value []byte) (int64, error) {
+	t := db.hashTx
 	t.Lock()
 	defer t.Unlock()
 
-	n, err := a.hash_setItem(key, field, value)
+	n, err := db.hSetItem(key, field, value)
 	if err != nil {
 		return 0, err
 	}
@@ -125,26 +125,26 @@ func (a *App) hash_set(key []byte, field []byte, value []byte) (int64, error) {
 	return n, err
 }
 
-func (a *App) hash_get(key []byte, field []byte) ([]byte, error) {
-	return a.db.Get(encode_hash_key(key, field))
+func (db *DB) HGet(key []byte, field []byte) ([]byte, error) {
+	return db.db.Get(encode_hash_key(key, field))
 }
 
-func (a *App) hash_mset(key []byte, args [][]byte) error {
-	t := a.hashTx
+func (db *DB) HMset(key []byte, args [][]byte) error {
+	t := db.hashTx
 	t.Lock()
 	defer t.Unlock()
 
 	var num int64 = 0
 	for i := 0; i < len(args); i += 2 {
 		ek := encode_hash_key(key, args[i])
-		if v, _ := a.db.Get(ek); v == nil {
+		if v, _ := db.db.Get(ek); v == nil {
 			num++
 		}
 
 		t.Put(ek, args[i+1])
 	}
 
-	if _, err := a.hash_incrSize(key, num); err != nil {
+	if _, err := db.hIncrSize(key, num); err != nil {
 		return err
 	}
 
@@ -153,10 +153,10 @@ func (a *App) hash_mset(key []byte, args [][]byte) error {
 	return err
 }
 
-func (a *App) hash_mget(key []byte, args [][]byte) ([]interface{}, error) {
+func (db *DB) HMget(key []byte, args [][]byte) ([]interface{}, error) {
 	r := make([]interface{}, len(args))
 	for i := 0; i < len(args); i++ {
-		v, err := a.db.Get(encode_hash_key(key, args[i]))
+		v, err := db.db.Get(encode_hash_key(key, args[i]))
 		if err != nil {
 			return nil, err
 		}
@@ -167,15 +167,15 @@ func (a *App) hash_mget(key []byte, args [][]byte) ([]interface{}, error) {
 	return r, nil
 }
 
-func (a *App) hash_del(key []byte, args [][]byte) (int64, error) {
-	t := a.hashTx
+func (db *DB) HDel(key []byte, args [][]byte) (int64, error) {
+	t := db.hashTx
 	t.Lock()
 	defer t.Unlock()
 
 	var num int64 = 0
 	for i := 0; i < len(args); i++ {
 		ek := encode_hash_key(key, args[i])
-		if v, err := a.db.Get(ek); err != nil {
+		if v, err := db.db.Get(ek); err != nil {
 			return 0, err
 		} else if v == nil {
 			continue
@@ -185,7 +185,7 @@ func (a *App) hash_del(key []byte, args [][]byte) (int64, error) {
 		}
 	}
 
-	if _, err := a.hash_incrSize(key, -num); err != nil {
+	if _, err := db.hIncrSize(key, -num); err != nil {
 		return 0, err
 	}
 
@@ -194,10 +194,10 @@ func (a *App) hash_del(key []byte, args [][]byte) (int64, error) {
 	return num, err
 }
 
-func (a *App) hash_incrSize(key []byte, delta int64) (int64, error) {
-	t := a.hashTx
+func (db *DB) hIncrSize(key []byte, delta int64) (int64, error) {
+	t := db.hashTx
 	sk := encode_hsize_key(key)
-	size, err := Int64(a.db.Get(sk))
+	size, err := Int64(db.db.Get(sk))
 	if err != nil {
 		return 0, err
 	} else {
@@ -213,22 +213,22 @@ func (a *App) hash_incrSize(key []byte, delta int64) (int64, error) {
 	return size, nil
 }
 
-func (a *App) hash_incrby(key []byte, field []byte, delta int64) (int64, error) {
-	t := a.hashTx
+func (db *DB) HIncrBy(key []byte, field []byte, delta int64) (int64, error) {
+	t := db.hashTx
 	t.Lock()
 	defer t.Unlock()
 
 	ek := encode_hash_key(key, field)
 
 	var n int64 = 0
-	n, err := StrInt64(a.db.Get(ek))
+	n, err := StrInt64(db.db.Get(ek))
 	if err != nil {
 		return 0, err
 	}
 
 	n += delta
 
-	_, err = a.hash_setItem(key, field, StrPutInt64(n))
+	_, err = db.hSetItem(key, field, StrPutInt64(n))
 	if err != nil {
 		return 0, err
 	}
@@ -238,13 +238,13 @@ func (a *App) hash_incrby(key []byte, field []byte, delta int64) (int64, error)
 	return n, err
 }
 
-func (a *App) hash_getall(key []byte) ([]interface{}, error) {
+func (db *DB) HGetAll(key []byte) ([]interface{}, error) {
 	start := encode_hash_start_key(key)
 	stop := encode_hash_stop_key(key)
 
 	v := make([]interface{}, 0, 16)
 
-	it := a.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
+	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
 	for ; it.Valid(); it.Next() {
 		_, k, err := decode_hash_key(it.Key())
 		if err != nil {
@@ -259,13 +259,13 @@ func (a *App) hash_getall(key []byte) ([]interface{}, error) {
 	return v, nil
 }
 
-func (a *App) hash_keys(key []byte) ([]interface{}, error) {
+func (db *DB) HKeys(key []byte) ([]interface{}, error) {
 	start := encode_hash_start_key(key)
 	stop := encode_hash_stop_key(key)
 
 	v := make([]interface{}, 0, 16)
 
-	it := a.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
+	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
 	for ; it.Valid(); it.Next() {
 		_, k, err := decode_hash_key(it.Key())
 		if err != nil {
@@ -279,13 +279,13 @@ func (a *App) hash_keys(key []byte) ([]interface{}, error) {
 	return v, nil
 }
 
-func (a *App) hash_values(key []byte) ([]interface{}, error) {
+func (db *DB) HValues(key []byte) ([]interface{}, error) {
 	start := encode_hash_start_key(key)
 	stop := encode_hash_stop_key(key)
 
 	v := make([]interface{}, 0, 16)
 
-	it := a.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
+	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
 	for ; it.Valid(); it.Next() {
 		v = append(v, it.Value())
 	}
@@ -295,10 +295,10 @@ func (a *App) hash_values(key []byte) ([]interface{}, error) {
 	return v, nil
 }
 
-func (a *App) hash_clear(key []byte) (int64, error) {
+func (db *DB) HClear(key []byte) (int64, error) {
 	sk := encode_hsize_key(key)
 
-	t := a.hashTx
+	t := db.hashTx
 	t.Lock()
 	defer t.Unlock()
 
@@ -306,7 +306,7 @@ func (a *App) hash_clear(key []byte) (int64, error) {
 	stop := encode_hash_stop_key(key)
 
 	var num int64 = 0
-	it := a.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
+	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
 	for ; it.Valid(); it.Next() {
 		t.Delete(it.Key())
 		num++
diff --git a/ledis/t_kv.go b/ledis/t_kv.go
index 2fd146f..bf273fb 100644
--- a/ledis/t_kv.go
+++ b/ledis/t_kv.go
@@ -21,101 +21,17 @@ func decode_kv_key(ek []byte) ([]byte, error) {
 	return ek[1:], nil
 }
 
-func (a *App) kv_get(key []byte) ([]byte, error) {
-	key = encode_kv_key(key)
-
-	return a.db.Get(key)
-}
-
-func (a *App) kv_set(key []byte, value []byte) error {
+func (db *DB) incr(key []byte, delta int64) (int64, error) {
 	key = encode_kv_key(key)
 	var err error
 
-	t := a.kvTx
-
-	t.Lock()
-	defer t.Unlock()
-
-	t.Put(key, value)
-
-	//todo, binlog
-
-	err = t.Commit()
-
-	return err
-}
-
-func (a *App) kv_getset(key []byte, value []byte) ([]byte, error) {
-	key = encode_kv_key(key)
-
-	t := a.kvTx
-
-	t.Lock()
-	defer t.Unlock()
-
-	oldValue, err := a.db.Get(key)
-	if err != nil {
-		return nil, err
-	}
-
-	t.Put(key, value)
-	//todo, binlog
-
-	err = t.Commit()
-
-	return oldValue, err
-}
-
-func (a *App) kv_setnx(key []byte, value []byte) (int64, error) {
-	key = encode_kv_key(key)
-	var err error
-
-	var n int64 = 1
-
-	t := a.kvTx
-
-	t.Lock()
-	defer t.Unlock()
-
-	if v, err := a.db.Get(key); err != nil {
-		return 0, err
-	} else if v != nil {
-		n = 0
-	} else {
-		t.Put(key, value)
-
-		//todo binlog
-
-		err = t.Commit()
-	}
-
-	return n, err
-}
-
-func (a *App) kv_exists(key []byte) (int64, error) {
-	key = encode_kv_key(key)
-	var err error
-
-	var v []byte
-	v, err = a.db.Get(key)
-	if v != nil && err == nil {
-		return 1, nil
-	} else {
-		return 0, err
-	}
-}
-
-func (a *App) kv_incr(key []byte, delta int64) (int64, error) {
-	key = encode_kv_key(key)
-	var err error
-
-	t := a.kvTx
+	t := db.kvTx
 
 	t.Lock()
 	defer t.Unlock()
 
 	var n int64
-	n, err = StrInt64(a.db.Get(key))
+	n, err = StrInt64(db.db.Get(key))
 	if err != nil {
 		return 0, err
 	}
@@ -130,12 +46,20 @@ func (a *App) kv_incr(key []byte, delta int64) (int64, error) {
 	return n, err
 }
 
-func (a *App) tx_del(keys [][]byte) (int64, error) {
+func (db *DB) Decr(key []byte) (int64, error) {
+	return db.incr(key, -1)
+}
+
+func (db *DB) DecrBy(key []byte, decrement int64) (int64, error) {
+	return db.incr(key, decrement)
+}
+
+func (db *DB) Del(keys [][]byte) (int64, error) {
 	for i := range keys {
 		keys[i] = encode_kv_key(keys[i])
 	}
 
-	t := a.kvTx
+	t := db.kvTx
 
 	t.Lock()
 	defer t.Unlock()
@@ -149,8 +73,72 @@ func (a *App) tx_del(keys [][]byte) (int64, error) {
 	return int64(len(keys)), err
 }
 
-func (a *App) tx_mset(args [][]byte) error {
-	t := a.kvTx
+func (db *DB) Exists(key []byte) (int64, error) {
+	key = encode_kv_key(key)
+	var err error
+
+	var v []byte
+	v, err = db.db.Get(key)
+	if v != nil && err == nil {
+		return 1, nil
+	}
+
+	return 0, err
+}
+
+func (db *DB) Get(key []byte) ([]byte, error) {
+	key = encode_kv_key(key)
+
+	return db.db.Get(key)
+}
+
+func (db *DB) GetSet(key []byte, value []byte) ([]byte, error) {
+	key = encode_kv_key(key)
+
+	t := db.kvTx
+
+	t.Lock()
+	defer t.Unlock()
+
+	oldValue, err := db.db.Get(key)
+	if err != nil {
+		return nil, err
+	}
+
+	t.Put(key, value)
+	//todo, binlog
+
+	err = t.Commit()
+
+	return oldValue, err
+}
+
+func (db *DB) Incr(key []byte) (int64, error) {
+	return db.incr(key, 1)
+}
+
+func (db *DB) IncryBy(key []byte, increment int64) (int64, error) {
+	return db.incr(key, increment)
+}
+
+func (db *DB) MGet(keys [][]byte) ([]interface{}, error) {
+	values := make([]interface{}, len(keys))
+
+	for i := range keys {
+		key := encode_kv_key(keys[i])
+		value, err := db.db.Get(key)
+		if err != nil {
+			return nil, err
+		}
+
+		values[i] = value
+	}
+
+	return values, nil
+}
+
+func (db *DB) MSet(args [][]byte) error {
+	t := db.kvTx
 
 	t.Lock()
 	defer t.Unlock()
@@ -168,18 +156,46 @@ func (a *App) tx_mset(args [][]byte) error {
 	return err
 }
 
-func (a *App) kv_mget(args [][]byte) ([]interface{}, error) {
-	values := make([]interface{}, len(args))
+func (db *DB) Set(key []byte, value []byte) error {
+	key = encode_kv_key(key)
+	var err error
 
-	for i := range args {
-		key := encode_kv_key(args[i])
-		value, err := a.db.Get(key)
-		if err != nil {
-			return nil, err
-		}
+	t := db.kvTx
 
-		values[i] = value
+	t.Lock()
+	defer t.Unlock()
+
+	t.Put(key, value)
+
+	//todo, binlog
+
+	err = t.Commit()
+
+	return err
+}
+
+func (db *DB) SetNX(key []byte, value []byte) (int64, error) {
+	key = encode_kv_key(key)
+	var err error
+
+	var n int64 = 1
+
+	t := db.kvTx
+
+	t.Lock()
+	defer t.Unlock()
+
+	if v, err := db.db.Get(key); err != nil {
+		return 0, err
+	} else if v != nil {
+		n = 0
+	} else {
+		t.Put(key, value)
+
+		//todo binlog
+
+		err = t.Commit()
 	}
 
-	return values, nil
+	return n, err
 }
diff --git a/ledis/t_list.go b/ledis/t_list.go
index af6f484..270331f 100644
--- a/ledis/t_list.go
+++ b/ledis/t_list.go
@@ -70,69 +70,13 @@ func decode_list_key(ek []byte) (key []byte, seq int32, err error) {
 	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 int32) (int64, error) {
-	ek := encode_list_key(key, whereSeq)
-
-	return Int64(a.db.Get(ek))
-}
-
-func (a *App) list_getMeta(ek []byte) (headSeq int32, tailSeq int32, size int32, err error) {
-	var v []byte
-	v, err = a.db.Get(ek)
-	if err != nil {
-		return
-	} else if v == nil {
-		size = 0
-		return
-	} else {
-		headSeq = int32(binary.LittleEndian.Uint32(v[0:4]))
-		tailSeq = int32(binary.LittleEndian.Uint32(v[4:8]))
-		size = int32(binary.LittleEndian.Uint32(v[8:]))
-	}
-	return
-}
-
-func (a *App) list_setMeta(ek []byte, headSeq int32, tailSeq int32, size int32) {
-	t := a.listTx
-
-	buf := make([]byte, 12)
-
-	binary.LittleEndian.PutUint32(buf[0:4], uint32(headSeq))
-	binary.LittleEndian.PutUint32(buf[4:8], uint32(tailSeq))
-	binary.LittleEndian.PutUint32(buf[8:], uint32(size))
-
-	t.Put(ek, buf)
-}
-
-func (a *App) list_len(key []byte) (int64, error) {
-	ek := encode_lmeta_key(key)
-	_, _, size, err := a.list_getMeta(ek)
-	return int64(size), err
-}
-
-func (a *App) list_push(key []byte, args [][]byte, whereSeq int32) (int64, error) {
-	t := a.listTx
+func (db *DB) lpush(key []byte, args [][]byte, whereSeq int32) (int64, error) {
+	t := db.listTx
 	t.Lock()
 	defer t.Unlock()
 
 	metaKey := encode_lmeta_key(key)
-	headSeq, tailSeq, size, err := a.list_getMeta(metaKey)
+	headSeq, tailSeq, size, err := db.lGetMeta(metaKey)
 
 	if err != nil {
 		return 0, err
@@ -174,20 +118,20 @@ func (a *App) list_push(key []byte, args [][]byte, whereSeq int32) (int64, error
 		tailSeq = seq
 	}
 
-	a.list_setMeta(metaKey, headSeq, tailSeq, size)
+	db.lSetMeta(metaKey, headSeq, tailSeq, size)
 
 	err = t.Commit()
 
 	return int64(size), err
 }
 
-func (a *App) list_pop(key []byte, whereSeq int32) ([]byte, error) {
-	t := a.listTx
+func (db *DB) lpop(key []byte, whereSeq int32) ([]byte, error) {
+	t := db.listTx
 	t.Lock()
 	defer t.Unlock()
 
 	metaKey := encode_lmeta_key(key)
-	headSeq, tailSeq, size, err := a.list_getMeta(metaKey)
+	headSeq, tailSeq, size, err := db.lGetMeta(metaKey)
 
 	if err != nil {
 		return nil, err
@@ -204,7 +148,7 @@ func (a *App) list_pop(key []byte, whereSeq int32) ([]byte, error) {
 
 	itemKey := encode_list_key(key, seq)
 	var value []byte
-	value, err = a.db.Get(itemKey)
+	value, err = db.db.Get(itemKey)
 	if err != nil {
 		return nil, err
 	}
@@ -222,7 +166,7 @@ func (a *App) list_pop(key []byte, whereSeq int32) ([]byte, error) {
 			tailSeq = seq
 		}
 
-		a.list_setMeta(metaKey, headSeq, tailSeq, size)
+		db.lSetMeta(metaKey, headSeq, tailSeq, size)
 	}
 
 	//todo add binlog
@@ -230,7 +174,71 @@ func (a *App) list_pop(key []byte, whereSeq int32) ([]byte, error) {
 	return value, err
 }
 
-func (a *App) list_range(key []byte, start int32, stop int32) ([]interface{}, error) {
+func (db *DB) lGetSeq(key []byte, whereSeq int32) (int64, error) {
+	ek := encode_list_key(key, whereSeq)
+
+	return Int64(db.db.Get(ek))
+}
+
+func (db *DB) lGetMeta(ek []byte) (headSeq int32, tailSeq int32, size int32, err error) {
+	var v []byte
+	v, err = db.db.Get(ek)
+	if err != nil {
+		return
+	} else if v == nil {
+		size = 0
+		return
+	} else {
+		headSeq = int32(binary.LittleEndian.Uint32(v[0:4]))
+		tailSeq = int32(binary.LittleEndian.Uint32(v[4:8]))
+		size = int32(binary.LittleEndian.Uint32(v[8:]))
+	}
+	return
+}
+
+func (db *DB) lSetMeta(ek []byte, headSeq int32, tailSeq int32, size int32) {
+	t := db.listTx
+
+	buf := make([]byte, 12)
+
+	binary.LittleEndian.PutUint32(buf[0:4], uint32(headSeq))
+	binary.LittleEndian.PutUint32(buf[4:8], uint32(tailSeq))
+	binary.LittleEndian.PutUint32(buf[8:], uint32(size))
+
+	t.Put(ek, buf)
+}
+
+func (db *DB) LIndex(key []byte, index int32) ([]byte, error) {
+	var seq int32
+	headSeq, tailSeq, _, err := db.lGetMeta(encode_lmeta_key(key))
+	if err != nil {
+		return nil, err
+	}
+
+	if index >= 0 {
+		seq = headSeq + index
+	} else {
+		seq = tailSeq + index + 1
+	}
+
+	return db.db.Get(encode_list_key(key, seq))
+}
+
+func (db *DB) LLen(key []byte) (int64, error) {
+	ek := encode_lmeta_key(key)
+	_, _, size, err := db.lGetMeta(ek)
+	return int64(size), err
+}
+
+func (db *DB) LPop(key []byte) ([]byte, error) {
+	return db.lpop(key, listHeadSeq)
+}
+
+func (db *DB) LPush(key []byte, args [][]byte) (int64, error) {
+	return db.lpush(key, args, listHeadSeq)
+}
+
+func (db *DB) LRange(key []byte, start int32, stop int32) ([]interface{}, error) {
 	v := make([]interface{}, 0, 16)
 
 	var startSeq int32
@@ -240,7 +248,7 @@ func (a *App) list_range(key []byte, start int32, stop int32) ([]interface{}, er
 		return []interface{}{}, nil
 	}
 
-	headSeq, tailSeq, _, err := a.list_getMeta(encode_lmeta_key(key))
+	headSeq, tailSeq, _, err := db.lGetMeta(encode_lmeta_key(key))
 	if err != nil {
 		return nil, err
 	}
@@ -263,7 +271,7 @@ func (a *App) list_range(key []byte, start int32, stop int32) ([]interface{}, er
 		stopSeq = listMaxSeq
 	}
 
-	it := a.db.Iterator(encode_list_key(key, startSeq),
+	it := db.db.Iterator(encode_list_key(key, startSeq),
 		encode_list_key(key, stopSeq), leveldb.RangeClose, 0, -1)
 	for ; it.Valid(); it.Next() {
 		v = append(v, it.Value())
@@ -274,38 +282,30 @@ func (a *App) list_range(key []byte, start int32, stop int32) ([]interface{}, er
 	return v, nil
 }
 
-func (a *App) list_index(key []byte, index int32) ([]byte, error) {
-	var seq int32
-	headSeq, tailSeq, _, err := a.list_getMeta(encode_lmeta_key(key))
-	if err != nil {
-		return nil, err
-	}
-
-	if index >= 0 {
-		seq = headSeq + index
-	} else {
-		seq = tailSeq + index + 1
-	}
-
-	return a.db.Get(encode_list_key(key, seq))
+func (db *DB) RPop(key []byte) ([]byte, error) {
+	return db.lpop(key, listTailSeq)
 }
 
-func (a *App) list_clear(key []byte) (int64, error) {
+func (db *DB) RPush(key []byte, args [][]byte) (int64, error) {
+	return db.lpush(key, args, listTailSeq)
+}
+
+func (db *DB) LClear(key []byte) (int64, error) {
 	mk := encode_lmeta_key(key)
 
-	t := a.listTx
+	t := db.listTx
 	t.Lock()
 	defer t.Unlock()
 
 	metaKey := encode_lmeta_key(key)
-	headSeq, tailSeq, _, err := a.list_getMeta(metaKey)
+	headSeq, tailSeq, _, err := db.lGetMeta(metaKey)
 
 	if err != nil {
 		return 0, err
 	}
 
 	var num int64 = 0
-	it := a.db.Iterator(encode_list_key(key, headSeq),
+	it := db.db.Iterator(encode_list_key(key, headSeq),
 		encode_list_key(key, tailSeq), leveldb.RangeClose, 0, -1)
 	for ; it.Valid(); it.Next() {
 		t.Delete(it.Key())
diff --git a/ledis/t_zset.go b/ledis/t_zset.go
index ea0fae0..b46d397 100644
--- a/ledis/t_zset.go
+++ b/ledis/t_zset.go
@@ -8,6 +8,11 @@ import (
 	"strconv"
 )
 
+const (
+	MinScore int64 = -1<<63 + 1
+	MaxScore int64 = 1<<63 - 1
+)
+
 var errZSizeKey = errors.New("invalid zsize key")
 var errZSetKey = errors.New("invalid zset key")
 var errZScoreKey = errors.New("invalid zscore key")
@@ -146,16 +151,16 @@ func decode_zscore_key(ek []byte) (key []byte, member []byte, score int64, err e
 	return
 }
 
-func (a *App) zset_setItem(key []byte, score int64, member []byte) (int64, error) {
+func (db *DB) zSetItem(key []byte, score int64, member []byte) (int64, error) {
 	if score <= MinScore || score >= MaxScore {
 		return 0, errScoreOverflow
 	}
 
-	t := a.zsetTx
+	t := db.zsetTx
 
 	var exists int64 = 0
 	ek := encode_zset_key(key, member)
-	if v, err := a.db.Get(ek); err != nil {
+	if v, err := db.db.Get(ek); err != nil {
 		return 0, err
 	} else if v != nil {
 		exists = 1
@@ -176,11 +181,11 @@ func (a *App) zset_setItem(key []byte, score int64, member []byte) (int64, error
 	return exists, nil
 }
 
-func (a *App) zset_delItem(key []byte, member []byte, skipDelScore bool) (int64, error) {
-	t := a.zsetTx
+func (db *DB) zDelItem(key []byte, member []byte, skipDelScore bool) (int64, error) {
+	t := db.zsetTx
 
 	ek := encode_zset_key(key, member)
-	if v, err := a.db.Get(ek); err != nil {
+	if v, err := db.db.Get(ek); err != nil {
 		return 0, err
 	} else if v == nil {
 		//not exists
@@ -202,8 +207,8 @@ func (a *App) zset_delItem(key []byte, member []byte, skipDelScore bool) (int64,
 	return 1, nil
 }
 
-func (a *App) zset_add(key []byte, args []interface{}) (int64, error) {
-	t := a.zsetTx
+func (db *DB) ZAdd(key []byte, args []interface{}) (int64, error) {
+	t := db.zsetTx
 	t.Lock()
 	defer t.Unlock()
 
@@ -212,7 +217,7 @@ func (a *App) zset_add(key []byte, args []interface{}) (int64, error) {
 		score := args[i].(int64)
 		member := args[i+1].([]byte)
 
-		if n, err := a.zset_setItem(key, score, member); err != nil {
+		if n, err := db.zSetItem(key, score, member); err != nil {
 			return 0, err
 		} else if n == 0 {
 			//add new
@@ -220,7 +225,7 @@ func (a *App) zset_add(key []byte, args []interface{}) (int64, error) {
 		}
 	}
 
-	if _, err := a.zset_incrSize(key, num); err != nil {
+	if _, err := db.zIncrSize(key, num); err != nil {
 		return 0, err
 	}
 
@@ -229,10 +234,10 @@ func (a *App) zset_add(key []byte, args []interface{}) (int64, error) {
 	return num, err
 }
 
-func (a *App) zset_incrSize(key []byte, delta int64) (int64, error) {
-	t := a.zsetTx
+func (db *DB) zIncrSize(key []byte, delta int64) (int64, error) {
+	t := db.zsetTx
 	sk := encode_zsize_key(key)
-	size, err := Int64(a.db.Get(sk))
+	size, err := Int64(db.db.Get(sk))
 	if err != nil {
 		return 0, err
 	} else {
@@ -248,15 +253,15 @@ func (a *App) zset_incrSize(key []byte, delta int64) (int64, error) {
 	return size, nil
 }
 
-func (a *App) zset_card(key []byte) (int64, error) {
+func (db *DB) ZCard(key []byte) (int64, error) {
 	sk := encode_zsize_key(key)
-	size, err := Int64(a.db.Get(sk))
+	size, err := Int64(db.db.Get(sk))
 	return size, err
 }
 
-func (a *App) zset_score(key []byte, member []byte) ([]byte, error) {
+func (db *DB) ZScore(key []byte, member []byte) ([]byte, error) {
 	k := encode_zset_key(key, member)
-	score, err := Int64(a.db.Get(k))
+	score, err := Int64(db.db.Get(k))
 	if err != nil {
 		return nil, err
 	}
@@ -264,21 +269,21 @@ func (a *App) zset_score(key []byte, member []byte) ([]byte, error) {
 	return Slice(strconv.FormatInt(score, 10)), nil
 }
 
-func (a *App) zset_rem(key []byte, args [][]byte) (int64, error) {
-	t := a.zsetTx
+func (db *DB) ZRem(key []byte, args [][]byte) (int64, error) {
+	t := db.zsetTx
 	t.Lock()
 	defer t.Unlock()
 
 	var num int64 = 0
 	for i := 0; i < len(args); i++ {
-		if n, err := a.zset_delItem(key, args[i], false); err != nil {
+		if n, err := db.zDelItem(key, args[i], false); err != nil {
 			return 0, err
 		} else if n == 1 {
 			num++
 		}
 	}
 
-	if _, err := a.zset_incrSize(key, -num); err != nil {
+	if _, err := db.zIncrSize(key, -num); err != nil {
 		return 0, err
 	}
 
@@ -286,14 +291,14 @@ func (a *App) zset_rem(key []byte, args [][]byte) (int64, error) {
 	return num, err
 }
 
-func (a *App) zset_incrby(key []byte, delta int64, member []byte) ([]byte, error) {
-	t := a.zsetTx
+func (db *DB) ZIncrBy(key []byte, delta int64, member []byte) ([]byte, error) {
+	t := db.zsetTx
 	t.Lock()
 	defer t.Unlock()
 
 	ek := encode_zset_key(key, member)
 	var score int64 = delta
-	v, err := a.db.Get(ek)
+	v, err := db.db.Get(ek)
 	if err != nil {
 		return nil, err
 	} else if v != nil {
@@ -310,7 +315,7 @@ func (a *App) zset_incrby(key []byte, delta int64, member []byte) ([]byte, error
 			}
 		}
 	} else {
-		a.zset_incrSize(key, 1)
+		db.zIncrSize(key, 1)
 	}
 
 	t.Put(ek, PutInt64(score))
@@ -321,13 +326,13 @@ func (a *App) zset_incrby(key []byte, delta int64, member []byte) ([]byte, error
 	return Slice(strconv.FormatInt(score, 10)), err
 }
 
-func (a *App) zset_count(key []byte, min int64, max int64) (int64, error) {
+func (db *DB) ZCount(key []byte, min int64, max int64) (int64, error) {
 	minKey := encode_start_zscore_key(key, min)
 	maxKey := encode_stop_zscore_key(key, max)
 
 	rangeType := leveldb.RangeROpen
 
-	it := a.db.Iterator(minKey, maxKey, rangeType, 0, -1)
+	it := db.db.Iterator(minKey, maxKey, rangeType, 0, -1)
 	var n int64 = 0
 	for ; it.Valid(); it.Next() {
 		n++
@@ -337,10 +342,10 @@ func (a *App) zset_count(key []byte, min int64, max int64) (int64, error) {
 	return n, nil
 }
 
-func (a *App) zset_rank(key []byte, member []byte, reverse bool) (int64, error) {
+func (db *DB) zrank(key []byte, member []byte, reverse bool) (int64, error) {
 	k := encode_zset_key(key, member)
 
-	if v, err := a.db.Get(k); err != nil {
+	if v, err := db.db.Get(k); err != nil {
 		return 0, err
 	} else if v == nil {
 		return -1, nil
@@ -354,10 +359,10 @@ func (a *App) zset_rank(key []byte, member []byte, reverse bool) (int64, error)
 
 			if !reverse {
 				minKey := encode_start_zscore_key(key, MinScore)
-				it = a.db.Iterator(minKey, sk, leveldb.RangeClose, 0, -1)
+				it = db.db.Iterator(minKey, sk, leveldb.RangeClose, 0, -1)
 			} else {
 				maxKey := encode_stop_zscore_key(key, MaxScore)
-				it = a.db.RevIterator(sk, maxKey, leveldb.RangeClose, 0, -1)
+				it = db.db.RevIterator(sk, maxKey, leveldb.RangeClose, 0, -1)
 			}
 
 			var lastKey []byte = nil
@@ -381,23 +386,23 @@ func (a *App) zset_rank(key []byte, member []byte, reverse bool) (int64, error)
 	return -1, nil
 }
 
-func (a *App) zset_iterator(key []byte, min int64, max int64, offset int, limit int, reverse bool) *leveldb.Iterator {
+func (db *DB) zIterator(key []byte, min int64, max int64, offset int, limit int, reverse bool) *leveldb.Iterator {
 	minKey := encode_start_zscore_key(key, min)
 	maxKey := encode_stop_zscore_key(key, max)
 
 	if !reverse {
-		return a.db.Iterator(minKey, maxKey, leveldb.RangeClose, offset, limit)
+		return db.db.Iterator(minKey, maxKey, leveldb.RangeClose, offset, limit)
 	} else {
-		return a.db.RevIterator(minKey, maxKey, leveldb.RangeClose, offset, limit)
+		return db.db.RevIterator(minKey, maxKey, leveldb.RangeClose, offset, limit)
 	}
 }
 
-func (a *App) zset_remRange(key []byte, min int64, max int64, offset int, limit int) (int64, error) {
-	t := a.zsetTx
+func (db *DB) zRemRange(key []byte, min int64, max int64, offset int, limit int) (int64, error) {
+	t := db.zsetTx
 	t.Lock()
 	defer t.Unlock()
 
-	it := a.zset_iterator(key, min, max, offset, limit, false)
+	it := db.zIterator(key, min, max, offset, limit, false)
 	var num int64 = 0
 	for ; it.Valid(); it.Next() {
 		k := it.Key()
@@ -406,7 +411,7 @@ func (a *App) zset_remRange(key []byte, min int64, max int64, offset int, limit
 			continue
 		}
 
-		if n, err := a.zset_delItem(key, m, true); err != nil {
+		if n, err := db.zDelItem(key, m, true); err != nil {
 			return 0, err
 		} else if n == 1 {
 			num++
@@ -415,7 +420,7 @@ func (a *App) zset_remRange(key []byte, min int64, max int64, offset int, limit
 		t.Delete(k)
 	}
 
-	if _, err := a.zset_incrSize(key, -num); err != nil {
+	if _, err := db.zIncrSize(key, -num); err != nil {
 		return 0, err
 	}
 
@@ -425,7 +430,7 @@ func (a *App) zset_remRange(key []byte, min int64, max int64, offset int, limit
 	return num, err
 }
 
-func (a *App) zset_reverse(s []interface{}, withScores bool) []interface{} {
+func (db *DB) zReverse(s []interface{}, withScores bool) []interface{} {
 	if withScores {
 		for i, j := 0, len(s)-2; i < j; i, j = i+2, j-2 {
 			s[i], s[j] = s[j], s[i]
@@ -440,7 +445,11 @@ func (a *App) zset_reverse(s []interface{}, withScores bool) []interface{} {
 	return s
 }
 
-func (a *App) zset_range(key []byte, min int64, max int64, withScores bool, offset int, limit int, reverse bool) ([]interface{}, error) {
+func (db *DB) zRange(key []byte, min int64, max int64, withScores bool, offset int, limit int, reverse bool) ([]interface{}, error) {
+	if offset < 0 {
+		return []interface{}{}, nil
+	}
+
 	nv := 64
 	if limit > 0 {
 		nv = limit
@@ -455,9 +464,9 @@ func (a *App) zset_range(key []byte, min int64, max int64, withScores bool, offs
 	//if reverse and offset is 0, limit < 0, we may use forward iterator then reverse
 	//because leveldb iterator prev is slower than next
 	if !reverse || (offset == 0 && limit < 0) {
-		it = a.zset_iterator(key, min, max, offset, limit, false)
+		it = db.zIterator(key, min, max, offset, limit, false)
 	} else {
-		it = a.zset_iterator(key, min, max, offset, limit, true)
+		it = db.zIterator(key, min, max, offset, limit, true)
 	}
 
 	for ; it.Valid(); it.Next() {
@@ -475,12 +484,111 @@ func (a *App) zset_range(key []byte, min int64, max int64, withScores bool, offs
 	}
 
 	if reverse && (offset == 0 && limit < 0) {
-		v = a.zset_reverse(v, withScores)
+		v = db.zReverse(v, withScores)
 	}
 
 	return v, nil
 }
 
-func (a *App) zset_clear(key []byte) (int64, error) {
-	return a.zset_remRange(key, MinScore, MaxScore, 0, -1)
+func (db *DB) zParseLimit(key []byte, start int, stop int) (offset int, limit int, err error) {
+	if start < 0 || stop < 0 {
+		//refer redis implementation
+		var size int64
+		size, err = db.ZCard(key)
+		if err != nil {
+			return
+		}
+
+		llen := int(size)
+
+		if start < 0 {
+			start = llen + start
+		}
+		if stop < 0 {
+			stop = llen + stop
+		}
+
+		if start < 0 {
+			start = 0
+		}
+
+		if start >= llen {
+			offset = -1
+			return
+		}
+	}
+
+	if start > stop {
+		offset = -1
+		return
+	}
+
+	offset = start
+	limit = (stop - start) + 1
+	return
+}
+
+func (db *DB) ZClear(key []byte) (int64, error) {
+	return db.zRemRange(key, MinScore, MaxScore, 0, -1)
+}
+
+func (db *DB) ZRange(key []byte, start int, stop int, withScores bool) ([]interface{}, error) {
+	return db.ZRangeGeneric(key, start, stop, withScores, false)
+}
+
+//min and max must be inclusive
+//if no limit, set offset = 0 and count = -1
+func (db *DB) ZRangeByScore(key []byte, min int64, max int64,
+	withScores bool, offset int, count int) ([]interface{}, error) {
+	return db.ZRangeByScoreGeneric(key, min, max, withScores, offset, count, false)
+}
+
+func (db *DB) ZRank(key []byte, member []byte) (int64, error) {
+	return db.zrank(key, member, false)
+}
+
+func (db *DB) ZRemRangeByRank(key []byte, start int, stop int) (int64, error) {
+	offset, limit, err := db.zParseLimit(key, start, stop)
+	if err != nil {
+		return 0, err
+	}
+	return db.zRemRange(key, MinScore, MaxScore, offset, limit)
+}
+
+//min and max must be inclusive
+func (db *DB) ZRemRangeByScore(key []byte, min int64, max int64) (int64, error) {
+	return db.zRemRange(key, min, max, 0, -1)
+}
+
+func (db *DB) ZRevRange(key []byte, start int, stop int, withScores bool) ([]interface{}, error) {
+	return db.ZRangeGeneric(key, start, stop, withScores, true)
+}
+
+func (db *DB) ZRevRank(key []byte, member []byte) (int64, error) {
+	return db.zrank(key, member, true)
+}
+
+//min and max must be inclusive
+//if no limit, set offset = 0 and count = -1
+func (db *DB) ZRevRangeByScore(key []byte, min int64, max int64,
+	withScores bool, offset int, count int) ([]interface{}, error) {
+	return db.ZRangeByScoreGeneric(key, min, max, withScores, offset, count, true)
+}
+
+func (db *DB) ZRangeGeneric(key []byte, start int, stop int,
+	withScores bool, reverse bool) ([]interface{}, error) {
+	offset, limit, err := db.zParseLimit(key, start, stop)
+	if err != nil {
+		return nil, err
+	}
+
+	return db.zRange(key, MinScore, MaxScore, withScores, offset, limit, reverse)
+}
+
+//min and max must be inclusive
+//if no limit, set offset = 0 and count = -1
+func (db *DB) ZRangeByScoreGeneric(key []byte, min int64, max int64,
+	withScores bool, offset int, count int, reverse bool) ([]interface{}, error) {
+
+	return db.zRange(key, min, max, withScores, offset, count, reverse)
 }
diff --git a/ledis/tx.go b/ledis/tx.go
index 41d0133..38b6e01 100644
--- a/ledis/tx.go
+++ b/ledis/tx.go
@@ -8,21 +8,9 @@ import (
 type tx struct {
 	m sync.Mutex
 
-	app *App
-
 	wb *leveldb.WriteBatch
 }
 
-func (app *App) newTx() *tx {
-	t := new(tx)
-
-	t.app = app
-
-	t.wb = app.db.NewWriteBatch()
-
-	return t
-}
-
 func (t *tx) Close() {
 	t.wb.Close()
 }