TiFlash aggregation push down result is not correct

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table foo(a int, b int);
insert into foo values(0, NULL);
alter table foo set tiflash replica 1;
create table bar(a double not null, b decimal(65,0)  not null);
insert into bar values(0, 0);
alter table bar set tiflash replica 1;
set tidb_isolation_read_engines='tiflash';
select * from foo where a=all(select a from bar where bar.b=foo.b);
-- Empty set (0.08 sec)

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

+------+------+
| a    | b    |
+------+------+
|    0 | NULL |
+------+------+

3. What did you see instead (Required)

empty

4. What is your TiDB version? (Required)

Release Version: v9.0.0-beta.2.pre-445-g98a285f
Edition: Community
Git Commit Hash: 98a285f
Git Branch: HEAD
UTC Build Time: 2025-09-04 15:58:40
GoVersion: go1.23.12
Race Enabled: false
Check Table Before Drop: false
Store: tikv
Kernel Type: Classic

[guo-shaoge]

introduced by: #63327