add clear func

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

Author: AilinKid

pkg/planner/memo/task.go

@@ -47,7 +47,7 @@ func newTaskStack() *TaskStack {
 // Destroy indicates that when stack itself is useless like in the end of optimizing phase, we can destroy ourselves.
 func (ts *TaskStack) Destroy() {
 	// when a taskStack itself is useless, we can destroy itself actively.
-	ts.tasks = ts.tasks[:0]
+	clear(ts.tasks)
 	TaskStackPool.Put(ts)
 }
 

pkg/planner/memo/task_test.go

@@ -89,4 +89,7 @@ func TestTaskFunctionality(t *testing.T) {
 
 	// self destroy.
 	taskStack.Destroy()
+	taskTaskPool = TaskStackPool.Get()
+	require.Equal(t, len(taskTaskPool.(*TaskStack).tasks), 0)
+	require.Equal(t, cap(taskTaskPool.(*TaskStack).tasks), 4)
 }