WEIGHT_STRING() behaviour differs from MySQL

[dveeden]

Bug Report

1. Minimal reproduce step (Required)

Run this with mysqlsh --column-type-info ...:

SELECT WEIGHT_STRING('aéè€☺');

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

This is with MySQL 8.1.0:

sql> SELECT WEIGHT_STRING('aéè€☺');
Field 1
Name:      `WEIGHT_STRING('aéè€☺')`
Org_name:  ``
Catalog:   `def`
Database:  ``
Table:     ``
Org_table: ``
Type:      Bytes
DbType:    VAR_STRING
Collation: binary (63)
Length:    320
Decimals:  31
Flags:     BINARY 

+------------------------+
| WEIGHT_STRING('aéè€☺') |
+------------------------+
| 0x1C471CAA1CAA1C2A094A |
+------------------------+
1 row in set (0.0003 sec)

This is with MySQL 8.0.33 (and MySQL Client instead of MySQL Shell):

root [(none)] > SELECT WEIGHT_STRING('aéè€☺');
Field   1:  `WEIGHT_STRING('aéè€☺')`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       VAR_STRING
Collation:  binary (63)
Length:     320
Max_length: 10
Decimals:   31
Flags:      BINARY 


+------------------------------------------------------------+
| WEIGHT_STRING('aéè€☺')                                     |
+------------------------------------------------------------+
| 0x1C471CAA1CAA1C2A094A                                     |
+------------------------------------------------------------+
1 row in set (0.01 sec)

3. What did you see instead (Required)

sql> SELECT WEIGHT_STRING('aéè€☺');
Field 1
Name:      `WEIGHT_STRING('aéè€☺')`
Org_name:  ``
Catalog:   `def`
Database:  ``
Table:     ``
Org_table: ``
Type:      String               ← Different, MySQL has Bytes
DbType:    VAR_STRING
Collation: utf8mb4_bin (46)     ← Different, MySQL has "binary (63)"
Length:    0                    ← Different, MySQL has 320
Decimals:  31
Flags:     NOT_NULL             ← Different, MySQL has "BINARY"

+------------------------+
| WEIGHT_STRING('aéè€☺') |
+------------------------+
| aéè€☺                  |
+------------------------+
1 row in set (0.0005 sec)

4. What is your TiDB version? (Required)

Release Version: v7.3.0-alpha-224-g941415cfd0
Edition: Community
Git Commit Hash: 941415cfd007161df099c0d701140dd3962b87c2
Git Branch: utf8mb4-0900-ai-ci
UTC Build Time: 2023-08-01 10:58:52
GoVersion: go1.20.6
Race Enabled: false
Check Table Before Drop: false
Store: unistore