The latest from the MySQL community

I am not a fan of the MMM tool for managing MySQL replication. This is a topic of vigorous debate among different people, and even within Percona not everyone feels the same way, which is why I’m posting it here instead of on an official Percona blog. There is room for legitimate differences of opinion, and my opinion is just my opinion. Nonetheless, I think it’s important to share, because a lot of people think of MMM as a high availability tool, and that’s not a decision to take lightly. At some point I just have to step off the treadmill and write a blog post to create awareness of what I see as a really bad situation that needs to be stopped.

I like software that is well documented and formally tested. A lot of software is usable even if it isn’t created by perfectionists. But there are two major things in the MySQL world for which I think we can all agree we need strong guarantees of correctness. One is backups. The other is …

MySQL has the well earned reputation for ease-of-use and “15-minutes-to-success”, since we continually focus making the server easy to use. MySQL Workbench provides the visual tools for database design, development, and administration. However, many DBAs prefer using the command-line, and there are many tasks that require the creation scripts for doing the job.

To make it easier to work with the server, the latest release of the MySQL Workbench—version 5.2.31—contain a set of Python scripts intended to make the life easier for DBAs by providing easy-to-use utilities for common tasks, which were introduced in the blog MySQL Workbench: Utilities. The set currently consists of just a few utilities, but will expand over time.

The utilities available in the Workbench are:

…

If you follow my blog or twitter stream you might know I've recently been at Barcelona to attend the PHP Barcelona conference. Conferences are great for exchanging ideas one of the ideas I discussed with Combell's Thijs Feryn: They are a hosting company providing managed MySQL instances to their customers, as such they run multiple MySQL servers and each server serves a few of their customers. Now they have to provide every customer with database credentials, including a host name to connect to. The issue there is that a fixed hostname takes flexibility out of the setup. Say you have db1.example.com and db2.example.com over time you figure out that there are two high load customers on db1 while db2 is mostly idle. …

To automatically create Foreign Key relationships is a typical use case for developers working with the MyISAM storage engine. This has been a popular topic on the Blog and forums so we’re revisiting it here – with a new and improved plugin written in Python.

While the InnoDB storage engine supports foreign keys, MyISAM doesn’t, but developers often pick it for various reasons and leave the application to handle relationships itself. MySQL Workbench can be used to reverse engineer a database to a model to better visualize or maintain it. But since MyISAM doesn’t have foreign keys, databases that use it will be lacking a very important part of it’s structure in the diagrams. You can link the columns manually, using the relationship tool to link columns, but you can also automate that. Databases are usually created so that columns that represent relationships have names that follow some kind of convention or pattern. For …

What I'm up to lately (giving love to some projects):

* Fixing bugs in DBD::mysql, just released 4.015, 4.016, and next 4.017. I had a patch sent yesterday from a user/developer that I want to get out there
* Memcached::libmemcached - 0.4201 version - now using latest libmemcached 0.42. This is the only Perl client that supports binary protocol!

patg@patg-desktop:~/code_dev/perl-libmemcached$ PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" "test_harness(0, 'blib/lib', 'blib/arch')" t/12-set-get-binary.t
t/12-set-get-binary....ok                                                   
All tests successful.
Files=1, …

Wow, 15 years ago, on June 8th 1995, Rasmus announced PHP 1.0. Time for a personal look back:

I can't remember when I first went online. Out from the local BBS systems into the wide open net. It must have been around the same time. But soon I figured out that I needed my own homepage, so I created one, using black fonts on a green (#00ff00) background. I was proud. The only issue: I had no idea how to make it accessible to others, I had the HTML file local on the PC, but well, I still was proud. I was proud since the effect of this HTML with a little bit of JavaScript was way stronger than most of my BASIC stuff I did before.

A bit later, in 1998, a cousin brought a magazine about writing Perl CGI applications which caught my attention so I started learning about CGI and Perl and all the …

Everybody working on Unix or in the database world stumbles over Oracle Berkeley DB every now and then. DB is an Open Source embedded database used by applications like OpenLDAP or Postfix. Traditionally it followed mostly a key-value access pattern. Now what caught my attention was the fact that the recently released DB 5.0 provides an SQLite-like C API with the promise of providing better concurrency and performance than regular SQLite. Time to give it a shot.

So I grabbed the source distribution, checked the documentation and saw that I shall use the …

In a couple of recent consulting cases, I needed a tool to analyze how a log of queries accesses indexes and tables in the database, specifically, to find out which indexes are not used. I initially hacked together something similar to Daniel Nichter’s mysqlidxchk, but using the framework provided by Maatkit, which gave me a pretty good start right out of the box. This was useful in the very tight time constraints I was under, but was not a complete solution. Alas, I could not use anything like Percona’s enhancements for finding unused indexes.

So, in response to another consultant’s customer request (and sponsorship — thank you!) I spent more time actually writing a real tool in the Maatkit style, with full tests and all the rest of the usual goodies. The resulting …

Maatkit does more than just MySQL. I’ve just committed a new version of mk-query-digest, a powerful log analysis tool, with support for Posgtres logs, in both syslog and stderr format. I’m hoping that people will give this a spin in the real world. I have lots of test cases, but that’s never enough; I’m looking for people to crunch their logs and let me know if anything breaks.

A brief tutorial:

# Get it
$ wget http://www.maatkit.org/trunk/mk-query-digest

# Run it
$ perl mk-query-digest --type pglog /path/to/log/file

# Learn about it (search for the string "pglog")
$ perldoc mk-query-digest

I’m going to close comments on this blog post so I don’t get bug reports in the comments. If you have feedback, please post it to the Maatkit mailing list, or …

If there’s one thing that will always make me angry, it’s people that should not be editing my code going and editing my code. If you want to change something on the server and you have sudo privileges please let the real admin know beforehand. I don’t mind people improving processes or scripts but if [...]