Fun with Bugs #45 - On Some Bugs Fixed in MySQL 5.7.15

Oracle released MySQL 5.7.15 recently, earlier than expected. The reason for this "unexpected" release is not clear to me, but it could happen because of a couple of security related internal bug reports that got fixed:

• "It was possible to write log files ending with .ini or .cnf that later could be parsed as option files. The general query log and slow query log can no longer be written to a file ending with .ini or .cnf. (Bug #24388753)
• Privilege escalation was possible by exploiting the way REPAIR TABLE used temporary files. (Bug #24388746)"

Let me concentrate on the most important fixes to bugs and problems reported by Community users. First of all, in MySQL 5.7.15 one can just turn off InnoDB deadlock detection using the new  innodb_deadlock_detect dynamic server variable. Domas had explained the positive effect of this more than 6 years ago in his post. Some improvements to the way deadlock detection worked in MySQL happened in frames of fix for the Bug #49047 long time ago, but this time Oracle just implemented a way to disable check and rely on InnoDB lock wait timeout instead.

Other InnoDB-related fixes to problems reported in public bugs database include:

• Bug #82073 - "Crash with InnoDB Encryption, 5.7.13, FusionIO & innodb_flush_method=O_DIRECT". It was reported by my colleague from MariaDB, Chris Calender, and verified by other my colleague from MariaDB, Jan Lindström. Probably Bugs Verification Team in Oracle just had no access to proper hardware to verify this.
• Bug #79378 - "buf_block_align() makes incorrect assumptions about chunk size". This bug was reported by Alexey Kopytov, who had provided a patch.

There were several fixes to replication-related bugs:

• Bug #81675 - "mysqlbinlog does not free the existing connection before opening new remote one". It was reported by Laurynas Biveinis from Percona, who had also provided a patch, and verified by Umesh.
• Bug #80881 - "MTR: binlog test suite failed to cleanup (contribution)". This fix to the binlog test suit was contributed by Daniel Black and verified by Umesh.
• Bug #79867 - "unnecessary using temporary for update". This bug was reported by Zhang Yingqiangwho had also contributed a patch (that was not used after all, according to the comment from Oracle developer). It was verified by Umesh.

 Some more bugs from other categories were also fixed:

• Bug #82125 - "@@basedir sysvar value not normalized if set through the command line/INI file". It was reported by Georgi Kodinov from Oracle. It's funny that there is a typo in the release notes when this fix is described (pay attention to slashes):
  

  "If the basedir system variable was set at server startup from the command line or option file, the value was not normalized (on Windows, / was not replaced with /)"

• Bug #82097 is private. I can not say anything about it in addition to this:
  

  "kevent statement timer subsystem deinitialization was revised to avoid a mysqld hang during shutdown on OS X 10.12."

  I can repeat, though, my usual statement that in most cases making bugs private is a wrong thing to do. I feel myself personally insulted every time when I see that fixed bug report remains private.
• Bug #81666 - "The MYSQL_SERVER define not defined du to spelling error in plugin.cmake". It was reported by Magnus Blåudd who had provided a patch also.
• Bug #81587 - "Combining ALTER operations triggers table rebuild". This bug was reported by Daniël van Eeden and verified by Umesh.
• Bug #68972 - "Can't find temporary table". This bug (that could happen in a stored procedure or when prepared statements are used) was reported by Cyril Scetbon and verified by Miguel Solorzano.
• Bug #82019 - "Is client library supposed to retry EINTR indefinitely or not". It was reported by Laurynas Biveinis from Percona, who had also contributed patches later. This bug was verified formally by Sinisa Milivojevic.

To summarize, you should consider upgrade to MySQL 5.7.15 for sure if you use FusionIO or want to be able to disable InnoDB deadlock detection entirely, or if you consider security-related fixes in this release really important (I don't). Otherwise just check other fixes that could impact you positively, or just wait for 5.7.16...