Wednesday, April 2, 2014

Fun with Bugs #32 - some bugs I've reported in March

Comparing to the previous month I was not really productive bug reporter in March 2014 (partially because I spent few days at a nice FLOSS UK conference where I tried to give a session on PERFORMANCE_SCHEMA). Just 12 reports, of them 5 documentation requests are already closed. There are some interesting reports among other 7 to write about though.

But let me start with good (or not entirely good) news about my older report, Bug #71858 (easy way to crash MySQL with single SELECT statement, at least on Windows and maybe everywhere). The bug seems to be fixed by Oracle, but the fix will appear in 5.5.38, 5.6.18, and 5.7.5, not in recent official releases.

Off all the documentation requests I'd like to highlight this one, Bug #71916, "Manual does NOT explain locks set for UPDATE ... WHERE PK='const' properly". I was so much surprised to see even basic details about InnoDB locks ad monitoring them not entirely or correctly documented thatI even decided to submit a talk about this of next Oracle's MySQL Connect event (and I tried once, but then probably clicked at some wrong place and my submission disappeared).... Do you think this makes any sense, or should we better just wait for MySQL Documentation team to explain it all eventually?

Another important cases of the "missing manual"are presented by my Bug #72047, "Manual does not explain names for indexes generated for FOREIGN keys properly", that I've reported while trying to study what happens when MySQL creates index for the foreign key implicitly and then InnoDB "switches" to a new suitable index that is explicitly created later (more on this to be written one day...), and by the latest my report, Bug #72133, "Manual does not provide enough details about InnoDB FTS implementation".

While working on a (usual) customer issue about ibdata1 growing even with innodb_file_per_table=1 in MySQL 5.6 I've noted more serious missing detail about FTS implementation represented by a sever bug report, Bug #72132, "Auxiliary tables for InnoDB FTS indexes are always created in shared tablespace". Had you even noted tables like these?

mysql> select name, space from information_schema.innodb_sys_tables where name like 'test/FTS%';
+----------------------------------------------------+-------+
| name                                               | space |
+----------------------------------------------------+-------+
| test/FTS_000000000000002e_0000000000000059_INDEX_1 |     0 |
| test/FTS_000000000000002e_0000000000000059_INDEX_2 |     0 |
| test/FTS_000000000000002e_0000000000000059_INDEX_3 |     0 |
| test/FTS_000000000000002e_0000000000000059_INDEX_4 |     0 |
| test/FTS_000000000000002e_0000000000000059_INDEX_5 |     0 |
| test/FTS_000000000000002e_0000000000000059_INDEX_6 |     0 |
| test/FTS_000000000000002e_BEING_DELETED            |    35 |
| test/FTS_000000000000002e_BEING_DELETED_CACHE      |    36 |
| test/FTS_000000000000002e_CONFIG                   |    37 |
| test/FTS_000000000000002e_DELETED                  |    33 |
| test/FTS_000000000000002e_DELETED_CACHE            |    34 |
... 

Not only they are not documented anywhere outside this old article, but those *_INDEX_* ones are always created in shared tablespace! I consider this a server bug to fix, not just something to document.

Probably I am not the first one, but I consider this mysql client problem, Bug #72108, related to libedit now used by Oracle mysql client instead of readline really annoying... Some users even claim that other versions/forks of MySQl are already good enough just because they still use readline :)

Finally, one of my reports ended up as "Not a bug": Bug #71978, "Server silently allows to set PERFORMANCE_SCHEMA as default_storage_engine". I've got a kind and polite offer like this:
"Please double-check the documentation available at http://dev.mysql.com/doc/ and the instructions on how to report a bug at http://bugs.mysql.com/how-to-report.php"
that I probably has to be insulted by, as a person who had not only reported many dozens of good "Verified" valid bugs, but also the one who had a chance to use the same boilerplate standard reply for 7+ years and hardly used it more than maybe 10 times over these years... What's even more interesting, for a bug that was "Verified" by Oracle engineer (and my former manager in bugs verification team) originally I've got explanations (that I am thankful for) and kind offer:
"So your request is at best a feature request (and feel free to re-open as such). But I see little value in implementing this, specially since you're getting a meaningful error message."
So, I did that. I still wonder why the decision to make feature request out of it was not made without original reporter involved...

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