diff --git a/go/filer/cassandra_store/cassandra_store.go b/go/filer/cassandra_store/cassandra_store.go
index e602548db..1c2be8a8e 100644
--- a/go/filer/cassandra_store/cassandra_store.go
+++ b/go/filer/cassandra_store/cassandra_store.go
@@ -3,8 +3,6 @@ package cassandra_store
 import (
 	"fmt"
 
-	"github.com/chrislusf/seaweedfs/go/filer"
-	"github.com/chrislusf/seaweedfs/go/filer/flat_namespace"
 	"github.com/chrislusf/seaweedfs/go/glog"
 
 	"github.com/gocql/gocql"
@@ -87,20 +85,3 @@ func (c *CassandraStore) Close() {
 		c.session.Close()
 	}
 }
-
-func (c *CassandraStore) FindDirectory(dirPath string) (dirId filer.DirectoryId, err error) {
-	return 0, flat_namespace.ErrNotImplemented
-}
-func (c *CassandraStore) ListDirectories(dirPath string) (dirs []filer.DirectoryEntry, err error) {
-	return nil, flat_namespace.ErrNotImplemented
-}
-func (c *CassandraStore) ListFiles(dirPath string, lastFileName string, limit int) (files []filer.FileEntry, err error) {
-	return nil, flat_namespace.ErrNotImplemented
-}
-func (c *CassandraStore) DeleteDirectory(dirPath string, recursive bool) (err error) {
-	return flat_namespace.ErrNotImplemented
-}
-
-func (c *CassandraStore) Move(fromPath string, toPath string) error {
-	return flat_namespace.ErrNotImplemented
-}
diff --git a/go/filer/flat_namespace/flat_namespace_filer.go b/go/filer/flat_namespace/flat_namespace_filer.go
index 2a2fd657b..9959b2924 100644
--- a/go/filer/flat_namespace/flat_namespace_filer.go
+++ b/go/filer/flat_namespace/flat_namespace_filer.go
@@ -29,16 +29,16 @@ func (filer *FlatNamespaceFiler) FindFile(fullFileName string) (fid string, err
 	return filer.store.Get(fullFileName)
 }
 func (filer *FlatNamespaceFiler) FindDirectory(dirPath string) (dirId filer.DirectoryId, err error) {
-	return filer.store.FindDirectory(dirPath)
+	return 0, ErrNotImplemented
 }
 func (filer *FlatNamespaceFiler) ListDirectories(dirPath string) (dirs []filer.DirectoryEntry, err error) {
-	return filer.store.ListDirectories(dirPath)
+	return nil, ErrNotImplemented
 }
 func (filer *FlatNamespaceFiler) ListFiles(dirPath string, lastFileName string, limit int) (files []filer.FileEntry, err error) {
-	return filer.store.ListFiles(dirPath, lastFileName, limit)
+	return nil, ErrNotImplemented
 }
 func (filer *FlatNamespaceFiler) DeleteDirectory(dirPath string, recursive bool) (err error) {
-	return filer.store.DeleteDirectory(dirPath, recursive)
+	return ErrNotImplemented
 }
 
 func (filer *FlatNamespaceFiler) DeleteFile(fullFileName string) (fid string, err error) {
@@ -46,5 +46,5 @@ func (filer *FlatNamespaceFiler) DeleteFile(fullFileName string) (fid string, er
 }
 
 func (filer *FlatNamespaceFiler) Move(fromPath string, toPath string) error {
-	return filer.store.Move(fromPath, toPath)
+	return ErrNotImplemented
 }
diff --git a/go/filer/flat_namespace/flat_namespace_store.go b/go/filer/flat_namespace/flat_namespace_store.go
index 8bb0d0a13..832b70e40 100644
--- a/go/filer/flat_namespace/flat_namespace_store.go
+++ b/go/filer/flat_namespace/flat_namespace_store.go
@@ -1,16 +1,9 @@
 package flat_namespace
 
-import "github.com/chrislusf/seaweedfs/go/filer"
+import ()
 
 type FlatNamespaceStore interface {
 	Put(fullFileName string, fid string) (err error)
 	Get(fullFileName string) (fid string, err error)
 	Delete(fullFileName string) (fid string, err error)
-
-	//redis store support these functions
-	FindDirectory(dirPath string) (dirId filer.DirectoryId, err error)
-	ListDirectories(dirPath string) (dirs []filer.DirectoryEntry, err error)
-	ListFiles(dirPath string, lastFileName string, limit int) (files []filer.FileEntry, err error)
-	DeleteDirectory(dirPath string, recursive bool) (err error)
-	Move(fromPath string, toPath string) error
 }