select using collation get wrong result

[xiongjiwei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a varchar(10) collate utf8mb4_bin, b varchar(10) collate utf8mb4_general_ci);
insert into t (a, b) values ('a', 'A');

select * from t where field('A', a collate utf8mb4_general_ci, b) > 1;

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

mysql> select * from t where field('A', a collate utf8mb4_general_ci, b) > 1;
Empty set (0.00 sec)

3. What did you see instead (Required)

mysql> select * from t where field('A', a collate utf8mb4_general_ci, b) > 1;
+------+------+
| a    | b    |
+------+------+
| a    | A    |
+------+------+
1 row in set (0.00 sec)

4. Affected version (Required)

master

5. Root Cause Analysis

[tabokie]

/label component/charset