The result of utf8mb4_general_ci collation with mpp is not correct

[lilinghai]

1.txt

source 1.txt
select `col_char(20)_undef_signed`,count( distinct `col_double_key_signed` ) as x from table_1000_utf8mb4collate_utf8mb4_general_ci_undef as t1 group by t1. `col_char(20)_undef_signed` having not exists (select `col_int_undef_unsigned` from table_1_binary_undef as t2 where  case when x then t2. `col_int_key_signed` else 1 end) order by `col_char(20)_undef_signed`;
-- expect the result value of column `col_char(20)_undef_signed` is same for the collation utf8mb4_general_ci
/*
explain select `col_char(20)_undef_signed`,count( distinct `col_double_key_signed` ) as x from table_1000_utf8mb4collate_utf8mb4_general_ci_undef as t1 group by t1. `col_char(20)_undef_signed` having not exists (select `col_int_undef_unsigned` from table_1_binary_undef as t2 where  case when x then t2. `col_int_key_signed` else 1 end) order by `col_char(20)_undef_signed`;
+------------------------------------------+----------+-------------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| id                                       | estRows  | task              | access object | operator info                                                                                                                                                                                                                                                                                                                                                                            |
+------------------------------------------+----------+-------------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Sort_11                                  | 6400.00  | root              |               | rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed                                                                                                                                                                                                                                                                                                          |
| └─TableReader_31                         | 6400.00  | root              |               | data:ExchangeSender_30                                                                                                                                                                                                                                                                                                                                                                   |
|   └─ExchangeSender_30                    | 6400.00  | batchCop[tiflash] |               | ExchangeType: PassThrough                                                                                                                                                                                                                                                                                                                                                                |
|     └─HashJoin_13                        | 6400.00  | batchCop[tiflash] |               | CARTESIAN anti semi join, other cond:case(Column#47, rs.table_1_binary_undef.col_int_key_signed, 1)                                                                                                                                                                                                                                                                                      |
|       ├─ExchangeReceiver_29(Build)       | 10000.00 | batchCop[tiflash] |               |                                                                                                                                                                                                                                                                                                                                                                                          |
|       │ └─ExchangeSender_28              | 10000.00 | batchCop[tiflash] |               | ExchangeType: Broadcast                                                                                                                                                                                                                                                                                                                                                                  |
|       │   └─TableFullScan_27             | 10000.00 | batchCop[tiflash] | table:t2      | keep order:false, stats:pseudo                                                                                                                                                                                                                                                                                                                                                           |
|       └─Projection_15(Probe)             | 8000.00  | batchCop[tiflash] |               | rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed, Column#47                                                                                                                                                                                                                                                                                               |
|         └─Projection_23                  | 8000.00  | batchCop[tiflash] |               | Column#47, rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed                                                                                                                                                                                                                                                                                               |
|           └─HashAgg_24                   | 8000.00  | batchCop[tiflash] |               | group by:rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed, funcs:count(distinct rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_double_key_signed)->Column#47, funcs:firstrow(rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed)->rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed |
|             └─ExchangeReceiver_26        | 8000.00  | batchCop[tiflash] |               |                                                                                                                                                                                                                                                                                                                                                                                          |
|               └─ExchangeSender_25        | 8000.00  | batchCop[tiflash] |               | ExchangeType: HashPartition, Hash Cols: [name: rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed, collate: utf8mb4_general_ci]                                                                                                                                                                                                                             |
|                 └─HashAgg_17             | 8000.00  | batchCop[tiflash] |               | group by:rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_char(20)_undef_signed, rs.table_1000_utf8mb4collate_utf8mb4_general_ci_undef.col_double_key_signed,                                                                                                                                                                                                                   |
|                   └─TableFullScan_22     | 10000.00 | batchCop[tiflash] | table:t1      | keep order:false, stats:pseudo                                                                                                                                                                                                                                                                                                                                                           |
+------------------------------------------+----------+-------------------+---------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
14 rows in set (0.04 sec)
*/

The unexpected result is as follows