wrong result when using index in enum column

[ChenPeng2013]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

use test;
drop table if exists PK_TCOLLATION3966STROBJSTROBJ;
CREATE TABLE `PK_TCOLLATION3966STROBJSTROBJ` (
  `COL1` enum('ll','aa','bb','cc','dd','ee') COLLATE utf8_general_ci NOT NULL,
  `COL2` varchar(20) COLLATE utf8_general_ci DEFAULT NULL,
  PRIMARY KEY (`COL1`) /*T![clustered_index] CLUSTERED */
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_general_ci;
insert into PK_TCOLLATION3966STROBJSTROBJ values("ee", "tttt");
SELECT col1, COL2 FROM PK_TCOLLATION3966STROBJSTROBJ WHERE COL1 IN ('notexist','6') and col2 not in ("abcd");

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

release-5.0

mysql> SELECT col1, COL2 FROM PK_TCOLLATION3966STROBJSTROBJ WHERE COL1 IN ('notexist','6') and col2 not in ("abcd");
Empty set (0.00 sec)

3. What did you see instead (Required)

release-5.1 & release-5.2 & master

mysql> SELECT col1, COL2 FROM PK_TCOLLATION3966STROBJSTROBJ WHERE COL1 IN ('notexist','6') and col2 not in ("abcd");
+------+------+
| col1 | COL2 |
+------+------+
| ee   | tttt |
+------+------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

Release Version: v5.2.0-alpha-747-g449e83236
Edition: Community
Git Commit Hash: 449e83236d097ec0100700e10bbb07ff84756dd9
Git Branch: master
UTC Build Time: 2021-08-26 10:02:01
GoVersion: go1.16.5
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[ti-srebot]

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