diff --git a/meta/meta.go b/meta/meta.go
index 1b9705e308..3f2ef0d59b 100644
--- a/meta/meta.go
+++ b/meta/meta.go
@@ -21,18 +21,24 @@ import (
 	"github.com/pingcap/tidb/kv"
 )
 
-const (
+var (
 	// SchemaMetaPrefix is the prefix for database meta key prefix.
-	SchemaMetaPrefix = "mDB:"
+	SchemaMetaPrefix = string(MakeMetaKey("mDB:"))
+
 	// TableMetaPrefix is the prefix for table meta key prefix.
-	TableMetaPrefix = "mTable:"
+	TableMetaPrefix = MakeMetaKey("mTable:")
+
+	// SchemaMetaVersionKey is used as lock for changing schema
+	SchemaMetaVersionKey = MakeMetaKey("mSchemaVersion")
+
+	// globalIDPrefix is used as key of global ID
+	globalIDKey = MakeMetaKey("mNextGlobalID")
 )
 
-var (
-	nextGlobalIDPrefix = []byte("mNextGlobalID")
-	// SchemaMetaVersionKey is used as lock for changing schema
-	SchemaMetaVersionKey = []byte("mSchemaVersion")
-)
+// MakeMetaKey creates meta key
+func MakeMetaKey(key string) []byte {
+	return append([]byte{0x0}, key...)
+}
 
 // GenID adds step to the value for key and returns the sum.
 func GenID(txn kv.Transaction, key []byte, step int) (int64, error) {
@@ -67,7 +73,7 @@ func AutoIDKey(tableID int64) string {
 // GenGlobalID generates the next id in the store scope.
 func GenGlobalID(store kv.Storage) (ID int64, err error) {
 	err = kv.RunInNewTxn(store, true, func(txn kv.Transaction) error {
-		ID, err = GenID(txn, []byte(nextGlobalIDPrefix), 1)
+		ID, err = GenID(txn, globalIDKey, 1)
 		if err != nil {
 			return errors.Trace(err)
 		}
diff --git a/meta/meta_test.go b/meta/meta_test.go
index 629bb36dd7..316990dbf8 100644
--- a/meta/meta_test.go
+++ b/meta/meta_test.go
@@ -49,14 +49,14 @@ func (*testSuite) TestT(c *C) {
 	c.Assert(err, NotNil)
 
 	// For DBMetaKey
-	mkey := meta.DBMetaKey(1)
-	c.Assert(mkey, Equals, "mDB::1")
+	mkey := []byte(meta.DBMetaKey(1))
+	c.Assert(mkey, DeepEquals, meta.MakeMetaKey("mDB::1"))
 
 	//For AutoIDKey
-	mkey = meta.AutoIDKey(1)
-	c.Assert(mkey, Equals, "mTable::1_autoID")
-	mkey = meta.AutoIDKey(0)
-	c.Assert(mkey, Equals, "mTable::0_autoID")
+	mkey = []byte(meta.AutoIDKey(1))
+	c.Assert(mkey, DeepEquals, meta.MakeMetaKey("mTable::1_autoID"))
+	mkey = []byte(meta.AutoIDKey(0))
+	c.Assert(mkey, DeepEquals, meta.MakeMetaKey("mTable::0_autoID"))
 
 	// For GenGlobalID
 	id, err = meta.GenGlobalID(store)
diff --git a/table/tables/tables.go b/table/tables/tables.go
index 404636cca3..901a7c77ee 100644
--- a/table/tables/tables.go
+++ b/table/tables/tables.go
@@ -534,6 +534,10 @@ func (t *Table) IterRecords(ctx context.Context, startKey string, cols []*column
 	}
 	defer it.Close()
 
+	if !it.Valid() {
+		return nil
+	}
+
 	log.Debugf("startKey %q, key:%q,value:%q", startKey, it.Key(), it.Value())
 
 	prefix := t.KeyPrefix()