FD loss in nested left join

[AilinKid]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Meta

create table customer1(pk int primary key, a int);
create table customer2(pk int primary key, b int);

Query

select c1.a, count(*) from customer2 c3 left join (customer1 c1 left join customer2 c2 on c1.a=c2.b) on c3.b=c1.a where c2.pk in (7,9) group by c2.b;

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

Empty set (0.01 sec)

3. What did you see instead (Required)

ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'test.c1.a' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

4. What is your TiDB version? (Required)

master

[AilinKid]

FD is introduced only in 6.0 and latter version.