Bug #83930 Wrong result when using like function with UCA collations

• Submitted: 23 Nov 2016 9:54
• Modified: 13 Dec 2016 17:26
• Reporter: Xing Zhang
• Status: Closed
• Category: MySQL Server: Charsets
• Severity: S3 (Non-critical)
• OS: Any
• CPU Architecture: Any

[23 Nov 2016 9:54] Xing Zhang

Description:
When using LIKE function with UCA collations like utf8mb4_unicode_520_ci, utf8mb4_0900_ai_ci, the result might be wrong.

For example:
mysql> set names latin1;
Query OK, 0 rows affected (0.00 sec)

mysql> select 'a\\' like 'a\\';
+------------------+
| 'a\\' like 'a\\' |
+------------------+
|                1 |
+------------------+
1 row in set (0.00 sec)

mysql> set names utf8mb4 collate utf8mb4_unicode_520_ci;
Query OK, 0 rows affected (0.00 sec)

mysql> select 'a\\' like 'a\\';
+------------------+
| 'a\\' like 'a\\' |
+------------------+
|                0 |
+------------------+
1 row in set (0.00 sec)

Obviously the result with utf8mb4_unicode_520_ci is wrong.

How to repeat:
As in Description.

Suggested fix:
N / A

[13 Dec 2016 17:26] Paul DuBois

Posted by developer:
 
Noted in 8.0.1 changelog.

For UCA collations, LIKE comparisons against a pattern that ended
with the escape character returned incorrect results.