Bug #82346 STRCMP() does not respect PADSPACE

• Submitted: 26 Jul 2016 11:40
• Modified: 26 Jul 2016 11:58
• Reporter: Alan Egerton
• Status: Not a Bug
• Category: MySQL Server
• Severity: S3 (Non-critical)
• Version: All
• OS: Any
• CPU Architecture: Any

[26 Jul 2016 11:40] Alan Egerton

Description:
The manual states that "STRCMP() performs the comparison using the collation of the arguments."[1]

The manual also  states that "All MySQL collations are of type PADSPACE."[2]

It is therefore inferred that STRCMP() will, like the `=` operator, pad the shorter string to the length of the longer before performing the comparison.  However, one does not observe this behaviour in practice.

[1]: https://dev.mysql.com/doc/en/string-comparison-functions.html#function_strcmp
[2]: https://dev.mysql.com/doc/en/char.html

How to repeat:
mysql> SELECT 'ab' = 'ab ', STRCMP('ab','ab ');
+--------------+--------------------+
| 'ab' = 'ab ' | STRCMP('ab','ab ') |
+--------------+--------------------+
|            1 |                  0 |
+--------------+--------------------+
1 row in set (0.00 sec)

Suggested fix:
Either the documentation needs to clarify that STRCMP() ignores the collation's PADSPACE characteristic, or else the implementation should be corrected.

[26 Jul 2016 11:58] Alan Egerton

Apologies, this was an idiotic bug report—a return value of 0 from STRCMP() is means equality, the same as a return value of 1 from the `=` operator.