Today I'll continue my series of posts about community bug reports I am subscribed to with the review of bugs reported since October 1, 2018, starting from the oldest and skipping those MySQL 8 regression ones I've already commented on:
- Bug #92609 - "Upgrade to 8.0.12 fails". This bug reported by Frederic Steinfels is about upgrade from MySQL 5.7 that leads to crash. Nice workaround was found:
"The work around is delete all .TRG file (or move them to out side of mysql data folder) then update. After success we can re-create the trigger."
The bug is really fixed in MySQL 8.0.14 according to the last comment, but for some reason it is still "Verified". Probably will be closed when MySQL 8.0.14 is released. - Bug #92631 - "importing dump from mysqldump --all-databases breaks SYS schema due to routines". This bug affecting MySQL 5.7 (and not 8.0) was reported by Shane Bester. Workaround is actually documented in the manual - add sys schema explicitly while dumping and dump it separately, then re-create.
- Bug #92661 - "SELECT on key partitioned enum reading all partitions instead of 1". Interesting corner case found by Frederic Steinfels. MariaDB 10.3.7 also seems affected:
MariaDB [test]> explain partitions select id from product where outdated='0';
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
| id | select_type | table | partitions | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
| 1 | SIMPLE | product | p0,p1 | ref | outdated | outdated |
1 | const | 2 | Using where; Using index |
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
1 row in set (0.002 sec)
MariaDB [test]> explain partitions select id from product where outdated='1';
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
| id | select_type | table | partitions | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
| 1 | SIMPLE | product | p0,p1 | ref | outdated | outdated |
1 | const | 2048 | Using where; Using index |
+------+-------------+---------+------------+------+---------------+----------+-
--------+-------+------+--------------------------+
1 row in set (0.002 sec) - Bug #92809 - "Inconsistent ResultSet for different Execution Plans". The full test case is not public and it took a lot of arguing until this bug (reported by Juan Arruti) was finally "Verified". Based on the workaround, setting optimizer_switch='materialization=off', this feature of MySQL optimizer is still problematic.
- Bug #92850 - "Bad select+order by+limit performance in 5.7". As Sveta Smirnova demonstrated, there are still cases when FORCE INDEX hints really needed to help optimizer to use proper plan, even in somewhat obvious case of single table and single proper index... What a surprise!
- Bug #92882 - "MTS not replication crash-safe with GTID and all the right parameters." As Jean-François Gagné proved, at least statement-based multi-threaded replication with GTIDs is not safe in case of OS crash. Good that there is an easy enough workaround: stop slave; reset slave; start slave; See also his Bug #93081 - "Please implement a better relay log recovery." that refers to several more known problems with relay log recovery.
- Bug #92949 - "add auto_increment column as PK cause RBR replication inconsistent". This probably should never happen in production (adding primary key while data are already active changed concurrently), but still this is a nice corner case reported by Fungo Wang.
- Bug #92996 - "ANALYZE TABLE still locks tables 10 years later". Domas Mituzas is trying hard to escalate this well known problem of blocking queries if ANALYZE TABLE was executed at some wrong time (when long running query against the table was in progress). The problem was resolved this year in Percona Server, see this blog post. See also my MDEV-15101 (fix is planned for version 10.4 in MariaDB).
- Bug #93033 - "Missing info on partitioned tables in I_S.INNODB_COLUMNS after upgrade to 8.0". Yet another regression in MySQL 8 vs 5.7 was reported by Alexey Kopytov.
- Bug #93049 - "ORDER BY pk, otherdata should just use PK". There is no reason to use filesort, as Domas Mituzas kindly noted. MariaDB is also, unfortunately, affected.
- Bug #93083 - "InnoDB: Failing assertion: srv_read_only_mode || trx->in_depth > 0". This Severity 6 bug (only debug binaries are directly affected) was reported by Ramesh Sivaraman from Percona QA. At least it was verified instantly (I've subscribed to double check what happens to bugs with low severity levels).
 | |
| Sheep are everywhere in East Sussex and bugs are everywhere in MySQL. Not that many, but still they are visible. |
- Sometimes it takes too much efforts to force proper bug report processing. I had written more about this here.
- Having materialization=on in optimizer_switch in MySQL 5.7+ may cause wrong results. Take care to double check.
- There still cases of single table SELECTs where optimizer can do a much better job. FORCE INDEX helps, sometimes.
- Multi-threaded statement-based replication in MySQL 5.6 and 5.7 is not crash safe, even with GTIDs, relay_log_info_repository-TABLE and relay_log_recovery=ON. A lot of improvements in relay log recovery are needed.
- Oracle engineers still care to document workarounds in active public bug reports. This is great!
- Percona still fixes some really important and annoying bugs way before other vendors.
- MySQL 8 is different in many small details, so regressions are to be expected.
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