MDEV-34817: Fix non-deterministic row order in perfschema.lowercase_fs_off

[kjarir]

Added ORDER BY object_schema, object_name to SELECT queries in lowercase_fs_off.test and updated the result file. This ensures stable row order in case-sensitive environments (MDEV-34817).

[gkodinov]

Thank you for your contribution. This is a preliminary review.

What you changed is not wrong. But I do not see how it fixes the jira at hand.

All reports in the Jira (the ones still available that is) are not about a stable sort order.

They are about either an extra row or a difference in count_start or count_statements.

Can you reproduce either of these? I was able to. But it wasn't about a stable order (see my comment in the jira).

Apparently something is not cleared in the cache somehow.

I would improve the test's stability by removing the extra counters from the SELECT statement: they're not really relevant to the test at hand: it's about how many rows do you see. I'd of course still report the original count issue as a separate jira should I go this way.

But, feel free to analyze the cache garbling case and fix that instead.
Note that I needed to do at least 10 iterations. 1 iteration wasn't enough.

Note also that adding an ORDER BY changes the execution plan by adding an extra filesort, which is probably not wha the test is supposed to do:

MariaDB [(none)]> explain SELECT object_type, object_schema, object_name, count_star, count_statements, sum_rows_sent FROM performance_schema.events_statements_summary_by_program WHERE object_type='procedure' AND LOWER(object_schema)='m33020_db1';
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-------------+
| id   | select_type | table                                | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-------------+
|    1 | SIMPLE      | events_statements_summary_by_program | ALL  | NULL          | NULL | NULL    | NULL | 0    | Using where |
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-------------+
1 row in set (0.006 sec)

MariaDB [(none)]> explain SELECT object_type, object_schema, object_name, count_star, count_statements, sum_rows_sent FROM performance_schema.events_statements_summary_by_program WHERE object_type='procedure' AND LOWER(object_schema)='m33020_db1' order by object_schema, object_name;
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-----------------------------+
| id   | select_type | table                                | type | possible_keys | key  | key_len | ref  | rows | Extra                       |
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-----------------------------+
|    1 | SIMPLE      | events_statements_summary_by_program | ALL  | NULL          | NULL | NULL    | NULL | 0    | Using where; Using filesort |
+------+-------------+--------------------------------------+------+---------------+------+---------+------+------+-----------------------------+
1 row in set (0.001 sec)