Fun with Bugs #66 – On MySQL Bug Reports I am Subscribed to, Part VI

I have some free time today, but I am still lazy enough to work on numerous planned and pending "ToDo" kind of posts, so why not to continue review of older MySQL bugs I am subscribed to. Today I am going to list 15 more bugs reported more than a year ago and still not fixed:
  • Bug #85805 - "Incorrect ER_BAD_NULL_ERROR after LOAD DATA LOCAL INFILE". This detailed bug report by Tsubasa Tanaka stays "Verified" for more than a year already. It's a great example of gdb use for MySQL troubleshooting. Setting a couple of breakpoints may really help to understand how MySQL works and why some weird errors happen.
  • Bug #85536 - "Build error on 5.5.54". It's clear that almost nobody besides Roel Van de Paar cares about build problem of MySQL 5.5.x(!) on Ubuntu 16.10(!). Anyway, it's strange that the bug remains "Verified" and not closed in any way if Oracle really does not intend to support MySQL 5.5 any longer. For now it seems MySQL 5.5 is still under extended support, so I hope to see this build problem fixed with some final 5.5.x release.
  • Bug #85501 - "Make all options settable as variables in configuration files". We usually see Umesh Shastry processing bugs reported by other, but this is a rare case when he reports something himself. It's a great feature request.
  • Bug #85447 - "Slave SQL thread locking issue on a certain XA workload on master". There are good reasons to think that this bug reported by Laurynas Biveinis may be fixed since MySQL 5.7.18, but no one cares to close it properly.
  • Bug #85382 - "Getting semi-sync reply magic number errors when slave_compressed_protocol is 1". This bug was reported by Jaime Sicam. Read also comments from other community members and make your own conclusions. It seems setting slave_compressed_protocol to 1 is a bad idea in general...
  • Bug #85191 - "performance regression with HANDLER READ syntax". Zhai Weixiang found clear performance regression in the way MySQL 5.7 uses metadata locking for HANDLER commands.
  • Bug #85016 - "better description for: OS error: 71". Clear and simple request from Shane Bester still stays "Verified". I am not that Oracle customer affected anyway, but this seems strange to me.
  • Bug #84958 - "InnoDB's MVCC has O(N^2) behaviors". This one bug report from Domas Mituzas could be a topic for a series of blog posts... It clearly states that:
    "if there're multiple row versions in InnoDB, reading one row from PK may have O(N) complexity and reading from secondary keys may have O(N^2) complexity"
    There is a patch that partially fixes the problem submitted by Laurynas Biveinis and created by Alexey Midenkov. While this bug is still "Verified" take carer when using secondary indexes in concurrent environments when the same data are often changed.
  • Bug #84868 - "Please make it possible to query replication information consistently". Great feature request (or bug report, if you consider inconsistency as a bug) from Simon Mudd.
  • Bug #84615 - "More steps in connection processlist state/ events_stages". Sveta Snirnova cared to ask to split some well known statement execution stages like "cleaning up" into more detailed ones. I think this is really important to simplify troubleshooting with performance_schema. Wrong/misleading/too generic stages forces to use other tools and may lead to wrong conclusions. I hit this with "statistics" also, see Bug #84858. Rare case when Sveta's request just stays "Open", for more than a year already.
  • Bug #84467 - "ALTERing KEY_BLOCK_SIZE keeps the old kbs in KEYs.". Jean-François Gagné and other well known bug reporters found several problems related to KEY_BLOCK_SIZE. It seems Oracle engineers decided NOT to fix them (see Bug #88220). But then why this bug still stays "Verified"? Consistency in bugs processing is one of my dreams...
  • Bug #84439 - "Table of row size of ~800 bytes does not compress with KEY_BLOCK_SIZE=1." Yet another bug report from Jean-François Gagné. Based on lack of activity, those looking for smaller data size, compression etc should look elsewhere and do not expect much from Oracle's InnoDB. Question is, what other engines with data compression will be supported by Oracle's MySQL 8 (or 9) GA? When you get tired wondering, consider MariaDB or Percona Server instead - they do support storage engines that are both transactional and were designed with write efficiency and space efficiency in mind. Hint: they rock...
  • Bug #84274 - "READ COMMITTED does not scale after 36 threads (in 5.6 after 16 threads)". Sveta Smirnova had a chance to run benchmarks on 144 cores (the largest box I ever had a chance to use for benchmarking had 12 cores, so what do I know...) and the result is clear - READ COMMITTED transaction isolation level does not scale well (comparing to default REPEATABLE READ). It's counter intuitive for many, but that's what we have. I doubt MySQL 8 is going to change this (unfortunate) situation.
  • Bug #84241 - "Potential Race Condition". This was found in MySQL 5.7 by Rui Gu with a little help from Helgrind.
  • Bug #84024 - "Optimizer thinks clustered primary key is not covering". This bug was reported by Manuel Ung. Let me quote a comment by Øystein Grøvlen:
    "I can agree that the cost model for join buffering is not perfect. If so, I think we should improve this model, not rely on heuristics about covering indexes versus table scan."
    I can not agree more! Let's hope this really happens in MySQL 9 at least.
You probably noted that we see mostly already famous bug reporters mentioned in this list. But names of reporters, their customer or partner status, known achievements, even clear regressions found or patches provided do not force Oracle to fix problems faster these days... They have their own agenda and great plans for MySQL, obviously.

I also have my own agenda, so I'll proceed with this glass of wine...

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