diff --git a/bootstrap.sh b/bootstrap.sh
index 40b737b..1cf49b6 100644
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -7,4 +7,4 @@ go get github.com/siddontang/go-snappy/snappy
 go get github.com/siddontang/copier
 
 go get github.com/syndtr/goleveldb/leveldb
-go get github.com/szferi/gomdb
\ No newline at end of file
+go get github.com/influxdb/gomdb
\ No newline at end of file
diff --git a/store/config.go b/store/config.go
index f2c8eee..b2939dc 100644
--- a/store/config.go
+++ b/store/config.go
@@ -5,10 +5,13 @@ type Config struct {
 
 	Path string
 
-	//for leveldb, goleveldb, rocksdb
+	//for leveldb, goleveldb
 	Compression     bool
 	BlockSize       int
 	WriteBufferSize int
 	CacheSize       int
 	MaxOpenFiles    int
+
+	//for lmdb
+	MapSize int
 }
diff --git a/store/mdb/batch.go b/store/mdb/batch.go
index 2bf2c04..60b6812 100644
--- a/store/mdb/batch.go
+++ b/store/mdb/batch.go
@@ -6,27 +6,27 @@ type Write struct {
 }
 
 type WriteBatch struct {
-	db MDB
+	db *MDB
 	wb []Write
 }
 
-func (w WriteBatch) Close() error {
+func (w *WriteBatch) Close() error {
 	return nil
 }
 
-func (w WriteBatch) Put(key, value []byte) {
+func (w *WriteBatch) Put(key, value []byte) {
 	w.wb = append(w.wb, Write{key, value})
 }
 
-func (w WriteBatch) Delete(key []byte) {
+func (w *WriteBatch) Delete(key []byte) {
 	w.wb = append(w.wb, Write{key, nil})
 }
 
-func (w WriteBatch) Commit() error {
+func (w *WriteBatch) Commit() error {
 	return w.db.BatchPut(w.wb)
 }
 
-func (w WriteBatch) Rollback() error {
+func (w *WriteBatch) Rollback() error {
 	w.wb = []Write{}
 	return nil
 }
diff --git a/store/mdb/mdb.go b/store/mdb/mdb.go
index ef9d2bf..038121a 100644
--- a/store/mdb/mdb.go
+++ b/store/mdb/mdb.go
@@ -20,7 +20,7 @@ type MDB struct {
 func Open(c *Config) (MDB, error) {
 	path := c.Path
 	if c.MapSize == 0 {
-		c.MapSize = 1 * 1024 * 1024 * 1024
+		c.MapSize = 10 * 1024 * 1024
 	}
 
 	env, err := mdb.NewEnv()
@@ -245,5 +245,5 @@ func (db MDB) NewIterator() driver.IIterator {
 }
 
 func (db MDB) NewWriteBatch() driver.IWriteBatch {
-	return WriteBatch{db, []Write{}}
+	return &WriteBatch{&db, []Write{}}
 }
diff --git a/store/store_test.go b/store/store_test.go
index b6fc70c..b911cb5 100644
--- a/store/store_test.go
+++ b/store/store_test.go
@@ -137,6 +137,16 @@ func TestIterator(t *testing.T) {
 		db.Put(key, value)
 	}
 
+	i = db.NewIterator()
+	i.SeekToFirst()
+
+	if !i.Valid() {
+		t.Fatal("must valid")
+	} else if string(i.Key()) != "key_0" {
+		t.Fatal(string(i.Key()))
+	}
+	i.Close()
+
 	var it *RangeLimitIterator
 
 	k := func(i int) []byte {
@@ -147,51 +157,67 @@ func TestIterator(t *testing.T) {
 	if err := checkIterator(it, 1, 2, 3, 4, 5); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
+
+	it = db.RangeLimitIterator(k(1), k(5), RangeClose, 0, -1)
+	if err := checkIterator(it, 1, 2, 3, 4, 5); err != nil {
+		t.Fatal(err)
+	}
+	it.Close()
 
 	it = db.RangeLimitIterator(k(1), k(5), RangeClose, 1, 3)
 	if err := checkIterator(it, 2, 3, 4); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RangeLimitIterator(k(1), k(5), RangeLOpen, 0, -1)
 	if err := checkIterator(it, 2, 3, 4, 5); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RangeLimitIterator(k(1), k(5), RangeROpen, 0, -1)
 	if err := checkIterator(it, 1, 2, 3, 4); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RangeLimitIterator(k(1), k(5), RangeOpen, 0, -1)
 	if err := checkIterator(it, 2, 3, 4); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RevRangeLimitIterator(k(1), k(5), RangeClose, 0, -1)
 	if err := checkIterator(it, 5, 4, 3, 2, 1); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RevRangeLimitIterator(k(1), k(5), RangeClose, 1, 3)
 	if err := checkIterator(it, 4, 3, 2); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RevRangeLimitIterator(k(1), k(5), RangeLOpen, 0, -1)
 	if err := checkIterator(it, 5, 4, 3, 2); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RevRangeLimitIterator(k(1), k(5), RangeROpen, 0, -1)
 	if err := checkIterator(it, 4, 3, 2, 1); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 
 	it = db.RevRangeLimitIterator(k(1), k(5), RangeOpen, 0, -1)
 	if err := checkIterator(it, 4, 3, 2); err != nil {
 		t.Fatal(err)
 	}
+	it.Close()
 }
 
 func TestCloseMore(t *testing.T) {