Saturday, April 27, 2019

Fun with Bugs #84 - On Some Public Bugs Fixed in MySQL 5.7.26

Oracle released minor MySQL Server versions in all supported branches on April 25, 2019. MySQL 5.7.26 is just one of them, but recently I prefer to ignore MySQL 8 releases (after checking that I can build them from source code at least somewhere, even if it takes 18G+ of disk space and that they work in basic tests), as there are more chances for MySQL 5.7 bug fixes to affect me (and customers I care about) directly.

So, in this yet another boring blog post (that would never be a reason for any award) I plan to concentrate on bugs reported in public MySQL bugs database and fixed in MySQL 5.7.26. As usual I name bug reporters explicitly and give links to their remaining currently active bug reports, if any. This time the list is short enough, so I do not even split it by categories:
  • Bug #93164 - "Memory leak in innochecksum utility detected by ASan". This bug was reported by Yura Sorokin from Percona, who also had contributed a patch (for some reason this is not mentioned in the official release notes).
  • Bug #90402 - "innodb async io error handling in io_event". Wei Zhao found yet another case when wrong data type was used in the code and I/O error was not handled, and this could lead even to crashes. He had submitted a patch.
  • Bug #89126 - "create table panic on innobase_parse_hint_from_comment". Nice bug report with a patch from Yan Huang. Note also detailed analysis and test case provided by Marcelo Altmann in the comment. It's a great example of cooperation of all sides: Oracle MySQL developers, bugs verification team, bug reporter and other community users.
  • Bug #92241 - "alter partitioned table add auto_increment diff result depending on algorithm". Yet another great finding from Shane Bester himself!
  • Bug #94247 - "Contribution: Fix fractional timeout values used with WAIT_FOR_EXECUTED_GTI ...". This bug report was created based on pull request from Dirkjan Bussink, who had suggested a patch to fix the problem. Note the comment from Shlomi Noach that refers to Bug #94311 (still private).
  • Bug #85158 - "heartbeats/fakerotate cause a forced sync_master_info". Note MTR test case contributed by Sveta Smirnova and code analysis in a comment from Vlad Lesin (both from Percona at that time) in this bug report from Trey Raymond.
  • Bug #92690 - "Group Replication split brain with faulty network". I do not care about group replication (I have enough Galera in my life instead), but I could not skip this report by Przemyslaw Malkowski from Percona, with detailed steps on how to reproduce. Note comments from other community members. Yet another case to show that good bug reports attract community feedback and are fixed relatively fast.
  • Bug #93750 - "Escaping of column names for GRANT statements does not persist in binary logs". Clear and simple bug report from Andrii Ustymenko. I wonder why it was not found by internal testing/QA. Quick test shows that MariaDB 10.3.7, for example, is not affected:
    c:\Program Files\MariaDB 10.3\bin>mysql -uroot -proot -P3316 test
    Welcome to the MariaDB monitor.  Commands end with ; or \g.
    Your MariaDB connection id is 9
    Server version: 10.3.7-MariaDB-log binary distribution

    Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    MariaDB [test]> create table t_from(id int primary key, `from` int, c1 int);
    Query OK, 0 rows affected (0.582 sec)

    MariaDB [test]> create user 'user01'@'%' identified by 'user01';
    Query OK, 0 rows affected (0.003 sec)

    MariaDB [test]> grant select (`id`,`from`) on `test`.`t_from` to 'user01'@'%';
    Query OK, 0 rows affected (0.054 sec)

    MariaDB [test]> show master status;
    | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
    | pc-PC-bin.000007 |      852 |              |                  |
    1 row in set (0.030 sec)

    MariaDB [test]> show binlog events in 'pc-PC-bin.000007';
    | Log_name         | Pos | Event_type        | Server_id | End_log_pos | Info
    | pc-PC-bin.000007 |   4 | Format_desc       |         1 |         256 | Server
    ver: 10.3.7-MariaDB-log, Binlog ver: 4                             |
    | pc-PC-bin.000007 | 256 | Gtid_list         |         1 |         299 | [0-1-42
    ]                                                                  |
    | pc-PC-bin.000007 | 299 | Binlog_checkpoint |         1 |         342 | pc-PC-b
    in.000007                                                          |
    | pc-PC-bin.000007 | 708 | Query             |         1 |         852 | use `te
    st`; grant select (`id`,`from`) on `test`.`t_from` to 'user01'@'%' |

    9 rows in set (0.123 sec)
  • Bug #73936 - "If the storage engine supports RBR, unsafe SQL statementes end up in binlog". Nice bug report with MTR test case by Santosh Praneeth Banda. Note that last comment about the fix mentions only MySQL 8.0.15, not a single work about the fix in MySQL 5.7.26 (or anything about MySQL 5.6.x while the bug was reported for 5.6).
  • Bug #93341 - "Check for tirpc needs improvement". The need for improvement of CMake check was noted by Terje Røsten.
  • Bug #91803 - "mysqladmin shutdown does not wait for MySQL to shut down anymore". This regression bug (without a "regression" tag) was reported by Christian Roser.
  • Bug #91541 - ""Flush status" statement adds twice to global values ". Yura Sorokin contributed a detailed anlysis, MTR test case and a patch in this bug reported by Carlos Tutte.
  • Bug #90351 - "GLOBAL STATUS variables drift after rollback". Zsolt Parragi contibuted a patch to this bug found and reported by Iwo P. For some reason this contribution is not highlighted in the release notes.
  • Bug #81441 - "Warning about localhost when using skip-name-resolve". One of many bug reports from Monty Solomon in which he (and other community members like Jean-François Gagné) had to spend a lot of efforts and fight with a member of bugs verification team to get the bug accepted as a real code bug and then get it fixed in all versions affected.
  • Bug #90902 - "Select Query With Complex Joins Leaks File Handles". This bug was reported by James Wilson. I still wonder if MySQL 5.6 was affected. Bug reports says nothing about this (while I expect all supported GA versions to be checked when the bug is verified, and the results of such check clearly documented).
The future looks bright for MySQL 5.7
To summarize:
  1. Consider upgrade to 5.7.26 if you use complex joins, partitioned tables with auto_increment columns or rely on InnoDB or replication a lot.
  2. It's good to see crashing bugs that do not end up as hidden/"security", maybe because they are reported with patches...
  3. It's good to see examples of cooperation of several community users contributing to the same bug report!
  4. Percona engineers contribute a lot to MySQL, both in form of bug reports, patches and by helping other community users to make their point and get their bugs fixed fast.
  5. There are still things to improve in a way Oracle egnineers handle bugs verification, IMHO.
  6.  It's also a bit strange to see only one optimizer-related fix in this release. It means that either MySQL optimizer is already near perfect and there are no bugs to fix (check yourself, but I see 123 bugs here), or that nobody cares that much about MySQL optimizer in 5.7 these days.
  7. It seems for some bugs fixed in previous MySQL 8.0.x minor release there is no extra check/updates in public comments about the versions with the fix when it is released in MySQL 5.6 or 5.7.

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