public static OptExpression bind(Pattern pattern, GroupExpression groupExpression) {
        Binder binder = new Binder(pattern, groupExpression);
        return binder.next();
    }
@Test
    public void testBinderTop() {
        OptExpression expr = OptExpression.create(new MockOperator(OperatorType.LOGICAL_JOIN),
                new OptExpression(new MockOperator(OperatorType.LOGICAL_OLAP_SCAN)),
                new OptExpression(new MockOperator(OperatorType.LOGICAL_OLAP_SCAN)));

        Pattern pattern = Pattern.create(OperatorType.LOGICAL_JOIN);

        Memo memo = new Memo();
        OptExpression result = Binder.bind(pattern, memo.init(expr));

        assertEquals(OperatorType.LOGICAL_JOIN, result.getOp().getOpType());
    }