Bug #94433 In mysql 8.0, result set of "group by" query is not sorted

• Submitted: 22 Feb 2019 1:15
• Modified: 22 Feb 2019 6:59
• Reporter: SeWoong Jeon
• Status: Not a Bug
• Category: MySQL Server: Optimizer
• Severity: S3 (Non-critical)
• Version: 8.0.15
• OS: CentOS (CentOS 7.5)
• CPU Architecture: x86 (x86_64)
• Tags: regression

[22 Feb 2019 1:15] SeWoong Jeon

Description:
In mysql 8.0, result set of "group by" query is not sorted.

mysql> select user, count(*) from mysql.user group by user;
+------------------+----------+
| user             | count(*) |
+------------------+----------+
| sbtest           |        2 | (!!)
| dbtest           |        2 |
| mysql.infoschema |        1 |
| mysql.session    |        1 |
| mysql.sys        |        1 |
| root             |        1 |
+------------------+----------+
6 rows in set (0.00 sec)

How to repeat:
.

Suggested fix:
sort the result set.

[22 Feb 2019 6:44] MySQL Verification Team

Hello SeWoong Jeon,

Thank you for the report.

regards,
Umesh

[22 Feb 2019 6:59] MySQL Verification Team

My colleague Shane pointed out that this is expected behavior and not a bug. Quoting from our manual - The deprecated ASC or DESC qualifiers for GROUP BY clauses are removed. Queries that previously relied on GROUP BY sorting may produce results that differ from previous MySQL versions. To produce a given sort order, provide an ORDER BY clause.

https://dev.mysql.com/doc/refman/8.0/en/mysql-nutshell.html