keyspace: return error if the split keyspace list is empty (tikv#7102)

close tikv#7101

Signed-off-by: JmPotato <[email protected]>

pkg/keyspace/tso_keyspace_group.go

@@ -675,6 +675,10 @@ func buildSplitKeyspaces(
 			newKeyspaceMap[keyspace] = struct{}{}
 		}
 	}
+	// Check if the new keyspace list is empty.
+	if len(newSplit) == 0 {
+		return nil, nil, ErrKeyspaceGroupWithEmptyKeyspace
+	}
 	// Get the split keyspace list for the old keyspace group.
 	oldSplit := make([]uint32, 0, oldNum-len(newSplit))
 	for _, keyspace := range old {

pkg/keyspace/tso_keyspace_group_test.go

@@ -542,8 +542,7 @@ func TestBuildSplitKeyspaces(t *testing.T) {
 			old:             []uint32{1, 2, 3, 4, 5},
 			startKeyspaceID: 7,
 			endKeyspaceID:   10,
-			expectedOld:     []uint32{1, 2, 3, 4, 5},
-			expectedNew:     []uint32{},
+			err:             ErrKeyspaceGroupWithEmptyKeyspace,
 		},
 		{
 			old: []uint32{1, 2, 3, 4, 5},

pkg/keyspace/util.go

@@ -76,6 +76,8 @@ var (
 	ErrNodeNotInKeyspaceGroup = errors.New("the tso node is not in this keyspace group")
 	// ErrKeyspaceGroupNotEnoughReplicas is used to indicate not enough replicas in the keyspace group.
 	ErrKeyspaceGroupNotEnoughReplicas = errors.New("not enough replicas in the keyspace group")
+	// ErrKeyspaceGroupWithEmptyKeyspace is used to indicate keyspace group with empty keyspace.
+	ErrKeyspaceGroupWithEmptyKeyspace = errors.New("keyspace group with empty keyspace")
 	// ErrModifyDefaultKeyspaceGroup is used to indicate that default keyspace group cannot be modified.
 	ErrModifyDefaultKeyspaceGroup = errors.New("default keyspace group cannot be modified")
 	// ErrNoAvailableNode is used to indicate no available node in the keyspace group.