Sunday, March 26, 2017

Fun with Bugs #51 - My Bug Reports that Oracle doesn't Want to Fix

This week I noticed (yet another) customer issue related to the output produced by mysqladmin debug command (or when mysqld process gets SIGHUP signal). I mean the output generated by the mysql_print_status() function. In this issue the content of the output was misinterpreted. I've seen this in the past more than once, and requested to document the output properly, but it never happened for a reason that there is an internal feature request to put this information elsewhere, in Performance Schema or Information Schema. The bug ended up with "Won't fix" status.

Surely I complained in a comment and on Facebook, and then decided to check if there are any other my bug reports and documentation request that Oracle explicitly decided not to fix after accepting the fact that there is a problem.

I've ended up with the following short list:
  • Bug #69399 - "Inconsistency in crash report". Here I've got a perfect reason to keep things as they are currently implemented. Functions called from signal handlers must be async signal safe, and time() is like that, but it always outputs in UTC. It would be great to print time in UTC in some messages as well, so that timezone difference is 100% clear, but it's truly not a big deal.
  • Bug #71300 - "Manual does not explain that statement/abstract/* instruments appeared in 5.6.15". This change in naming that happened in 5.6.15 is, indeed, explained in the manual, even if there is no highlighted statements about incompatible change etc. I can live with that.
  • Bug #71303 - "Manual page on P_S build configuration does not provide enough details". I really missed the details at that time on how to instrument individual buffer's mutexes/rwlocks, after getting a hint during my talk that I had no chance to see real most important waits in Bug #68079  with Performance Schema without recompiling it properly. I've got a useful comment at the end of the bug report, but I truly do not understand why this detail ("The only way to enable it is by removing the line which defines PFS_SKIP_BUFFER_MUTEX_RWLOCK in storage/innobase/include/sync0sync.h. Seems to be no compiler flags to enable or disable the above mentioned symbol.") was not added to the small enough page as a note.
  • Bug #71304 - "Manual does not provide enough details about automatic sizing of P_S parameters ". Here my suggestions were refused. Go figure yourself, check the output of mysqld --verbose --help 2>/dev/null | grep performance | grep "\-1" to find out what parameters are auto-sized and go read the code to find out how exactly, if you care. They don't.
  • Bug #71274 - "Manual does not provide enough details about background threads in P_S.threads". All I've got in reply is: "The purpose of the page is to describe the table structure, not enumerate the (subject to change) set of background threads." You may be satisfied with this remark, but I am not.
  • Bug #71346 - "Manual does not provide details on mysqladmin debug output". As you can check here, even for MySQL 8 the command is still there, but all we have about the output is: "Tell the server to write debug information to the error log. Format and content of this information is subject to change. This includes information about the Event Scheduler."
  • Bug #75366 - "mysql_install_db requires explicit --lc-messages-dir if non-default PREFIX used". This was reported at early MySQL 5.7.x development stage, and I've got a recommendation to use mysqld --initialize instead. I do so now, but sometimes some related problem still happen, see Bug #84173 and Bug #80351. I think that even deprecated commands must be properly documented, including any incompatible changes in behavior, options, binaries location etc, until they still exist in GA and supported versions of MySQL.
  • Bug #78822 - "Materialized table from semijoin may change join order and lead to bad plan". In MySQL 5.7 the problem must be fixed, and for 5.6 the following obvious workaround was suggested: set optimizer_switch="semijoin=off";
  • Bug #80601 - "Manual is wrong/not clear while explaining kill flag check for ALTER TABLE".  Even though it was stated that "this is an implementation detail subject to change", some clarifications happened in the manual.
To summarize, out of 310 bug reports I've created since 2005, Oracle decided not to fix just 9, and in many cases provided proper explanations about the reasons to do this, or made some changes in the manual. The remaining cases all are related to MySQL manual and mostly happened in 2014, when nice people found a way to shut me up (temporary) on the topic of MySQL bugs...

No comments:

Post a Comment