Bug #80227 Func SUBSTRING_INDEX works incorrectly with negative count

• Submitted: 2 Feb 2016 4:24
• Modified: 2 Feb 2016 6:18
• Reporter: Su Dylan
• Status: Verified
• Category: MySQL Server: DML
• Severity: S3 (Non-critical)
• Version: 5.7.8, 5.7.10, 5.6.28, 5.5.48
• OS: Any
• CPU Architecture: Any

[2 Feb 2016 4:24] Su Dylan

Description:
Output:
=====
mysql> select substring_index('aaab','aa',-1);
+---------------------------------+
| substring_index('aaab','aa',-1) |
+---------------------------------+
| ab                              |
+---------------------------------+
1 row in set (0.00 sec)

mysql> select version();
+-----------+
| version() |
+-----------+
| 5.7.8-rc  |
+-----------+
1 row in set (0.00 sec)

Problem:
=====
'b' is expected.

How to repeat:
select substring_index('aaab','aa',-1);

Suggested fix:
'b' is returned.

[2 Feb 2016 6:18] MySQL Verification Team

Hello Su Dylan,

Thank you for the report and test case.
Observed that 5.5.48, 5.6.28 and 5.7.10 are affected.

Thanks,
Umesh

[2 Feb 2016 7:44] Tor Didriksen

Posted by developer:
 
5.1 is also affected

select substring_index('aaab','aa',-1);
substring_index('aaab','aa',-1)
b
set names utf8;
select substring_index('aaab','aa',-1);
substring_index('aaab','aa',-1)
ab