Can't find column in schema Column: [] Unique key: [] when using hash_agg() hint and tiflash engine

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE `t1` (
  `a` bit(1) DEFAULT NULL,
  `b` bit(1) DEFAULT NULL,
  `c` bit(1) GENERATED ALWAYS AS (`a`) VIRTUAL
);
alter table t1 set tiflash replica 1;
set @@tidb_isolation_read_engines='tiflash';
select/*+ hash_agg() */ count(*) from t1 where c > 1;

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

successfully

3. What did you see instead (Required)

ERROR 1105 (HY000): Can't find column test.t1.a in schema Column: [test.t1.c] Unique key: []

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-2578-g6cff35892
Edition: Community
Git Commit Hash: 6cff358
Git Branch: master
UTC Build Time: 2021-04-07 06:23:51
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[ti-srebot]

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