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Displaying posts with tag: speculations (reset)
Fun with Bugs #54 - On Some Bugs Fixed in MySQL 5.7.19

More than 3 months after 5.7.18 we' ve got MySQL 5.7.19 released recently. This is my quick review of the release notes with interesting fixed bug (reported in public) highlighted in the areas I am usually interested in.

Let's start with InnoDB. The following bug fixes attracted my attention:

  • Bug #85043 is still private. You know how much I hate those. At least we can see it was about the fact that "The server allocated memory unnecessarily for an operation that rebuilt the table." Let's hope this is no longer the case.
  • Bug …
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Fun with Bugs #53 - On Some Percona Software Bugs I've Reported

So far in this series I had written only/mostly about MySQL server bugs. Does it mean that there are no unique or interesting bugs in other MySQL-related software or MySQL forks and projects that use MySQL code?

Surely no, it doesn't. So, today I'd like to present a short list of currently active (that is, new or probably not yet resolved) bugs that I had reported for Percona's software at Launchpad over the years I use it. The list is based on this link, but I excluded minor reports and those that probably are just forgotten, while the problem is fixed long time ago.

Let me start with bugs in XtraBackup, the tool that plays a key role in most MySQL environments that are not using Oracle's Enterprise …

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MySQL Support Engineer's Chronicles, Issue #7

This week in Support was busy enough for me. Among other things I had to study all possible reasons (other than obvious query cache impact) for queries hanging in "query end" status and noted Bug #80652 related to binlog group commit and fixed in MySQL 5.7.17+ and 8.0.1+ only. The case I had to review was related to Galera though, and I suggest you to note that "query end" may be related to Galera replication stall. Studying this path further soon brought lp:1197771 - "Cluster stalls while distributing transaction" to my attention again, so I asked about proper status for it on Facebook. As it happens way too often recently, I've got few 'Likes" but no further comments, neither …

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My First Steps with MariaDB ColumnStore

This is a "Howto" kind of post, and some speculations and historical references aside, it will show you how to build MariaDB ColumnStore (current version 1.0.9) from GitHub source, how to install and configure it for basic usage, as well as how to resolve some minor problems you may get in the process. Keep reading and eventually you'll get the real Howto below :)

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I try not to care about any software issues besides good old MySQL, InnoDB storage engine internals, query optimization and some MyRocks or a little bit of …

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Fun with Bugs #52 - On Some Bugs Fixed in MySQL 5.7.18

I had not reviewed MySQL 5.7 release notes for quite a some time in this series. Last time I checked it was MySQL 5.7.15. So, as soon as I noted new release, 5.7.18, I decided to check the release notes for any interesting fixed bug (reported by Community users in public) in the areas I am interested in: InnoDB, replication, optimizer and few others.

Note that recently most of the bugs fixed are internal only, found by Oracle engineers that never cared (or are not allowed, who knows) to report them in public, so this blog post is not even remotely a full review of what's fixed in MySQL 5.7.18 and is not a replacement for reading the detailed …

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Accessing Oracle tables via MariaDB CONNECT engine and ODBC

In my previous working environment it was typical to consider MariaDB Server as just a set of "random" storage engines mixed together, sometimes for unclear reasons and with questionable extra value. But even at that times I was already impressed by some features of one of the engines supported only by MariaDB, CONNECT. PIVOT table type specifically was of interest in a couple of customer cases I had to work on, but I quickly found out that the engine does not work with Oracle's MySQL or Percona Server, and thus had to forget about it for some time.

Recently while working in MariaDB I've got several more chances to deal with some new CONNECT use cases (and some related problems, that ended up mostly minor or caused by ignorance). This engine …

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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 …

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Fun with Bugs #50 - On Bugs Tagged as "missing manual"

Back in January 2014, some time after many nice people kindly asked me to shut up stop writing about MySQL bugs on Facebook several times per day, I decided to start reading the fine MySQL Manual more carefully than before and report not only typos there, but also any topic or detail not properly explained. Usually these reports, tagged as "missing manual", were the result of careful study of the documentation based on real user question or customer issue. So, most of these reports came from real life, and missing information badly affected poor MySQL users.

Today, for this issue #50 in my series of posts about MySQL bugs, I decided to list and …

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Testing MyRocks vs InnoDB Performance Using sysbench 1.x oltp_point_select.lua

It seems MyRocks is going to become a hot topic in April 2017. Previously (here and there) I tried to compare its performance and scalability vs InnoDB from MySQL 5.7.17 using test case from famous bug #68079. It's an interesting case that took a lot of efforts from Oracle to make InnoDB scale properly, and InnoDB (on my QuadCore box at least, others reported different results on other hardware in comments) still outperformed MyRocks. But maybe it's corner case that is not a big deal in general?

Earlier this month I decided to give MyRocks another chance and try it with "industry-standard" benchmarks, like those provided by

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Fun with Bugs #49 - Applying PMP to MySQL

As you maybe noted, in several recent posts I've provided some additional details for slides used during my FOSDEM talk on profiling MySQL. The only part not covered yet is related to using Poor Man's Profiler (and pt-pmp version of it). I see no reason to explain what it does and how to use it once again, but would like to show several recent enough MySQL bug reports where this tool was essential to find, explain or demonstrate the problem.

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