The global index not work with `memIndexLookUpReader` executor

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set tidb_enable_global_index=true;
CREATE TABLE `t` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL,
  UNIQUE KEY `idx1` (`b`),
  KEY `idx` (`b`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
PARTITION BY HASH (`a`) PARTITIONS 5;

begin;
insert into t values (1, 2), (2, 3);
select b from t use index(idx1) where b > 2;

2. What did you expect to see? (Required)

return result 3

3. What did you see instead (Required)

return empty

4. What is your TiDB version? (Required)