The predicate on the bit column cannot be pushed down

[rebelice]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int, b int, c bit(1), key(a, b, c));
explain select * from t where c=0 order by a, b limit 10;

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

+------------------------------+---------+-----------+---------------------------+-------------------------------+
| id                           | estRows | task      | access object             | operator info                 |
+------------------------------+---------+-----------+---------------------------+-------------------------------+
| Limit_12                     | 10.00   | root      |                           | offset:0, count:10            |
| └─IndexReader_30             | 10.00   | root      |                           | index:Limit_29                |
|   └─Limit_29                 | 10.00   | cop[tikv] |                           | offset:0, count:10            |
|     └─Selection_28           | 10.00   | cop[tikv] |                           | gt(test.t.c, 0)               |
|       └─IndexFullScan_27     | 30.00   | cop[tikv] | table:t, index:a(a, b, c) | keep order:true, stats:pseudo |
+------------------------------+---------+-----------+---------------------------+-------------------------------+

3. What did you see instead (Required)

+----------------------------+---------+-----------+----------------------------+-------------------------------+
| id                         | estRows | task      | access object              | operator info                 |
+----------------------------+---------+-----------+----------------------------+-------------------------------+
| Limit_14                   | 10.00   | root      |                            | offset:0, count:10            |
| └─Selection_21             | 10.00   | root      |                            | eq(test.t.c, 0)              |
|   └─IndexReader_23         | 10.00   | root      |                            | index:IndexFullScan_22        |
|     └─IndexFullScan_22     | 10.00   | cop[tikv] | table:t, index:a(a, b, c) | keep order:true, stats:pseudo |
+----------------------------+---------+-----------+----------------------------+-------------------------------+

4. What is your TiDB version? (Required)

Release Version: v5.4.0-alpha-411-g04a9618f5
Edition: Community
Git Commit Hash: 04a9618
Git Branch: HEAD
UTC Build Time: 2021-12-15 07:14:59
GoVersion: go1.17.3
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false