If MySQL in Tokyo is on floor six, who is on floor seven?

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Last friday I had a chance to give a talk at YAPC::Asia 2008 on the internals of Pathtraq, one of the largest web access stats service in Japan.

The talk covered from techniques we use for compressing data on MySQL tables, our cache architecture, and a mysql-based message queue (Q4M) that we developed and use.

The slides of the talk are available at http://www.slideshare.net/kazuho/yapcasia-2008-tokyo-pathtraq-building-a-computationcentric-web-service, so please have a look.

Last week I was working with a client that rediscovered a bug where setting expire_logs_days and issuing a flush logs causes the server to crash. It’s MySQL Bug #17733 if you want to have a look. Seeing MySQL crash was enough inspiration to fix something that I and others have wanted to fix in MySQL for years.

Currently a flush logs command tries to flush all of the following logs in order:

• General Log
• Slow Query Log
• Binary Log
• Relay Log
• Store Engine Logs (If available)
• Error Log

The reason I wanted to fix this is because my client was issuing a flush logs to rotate the error log on a server with no replication. The crash was caused by replication. With individual flush logs it’s less likely for this to happen again in the future. People can simply issue a query for the …

Instructions for adding a new Unicode collation

By Alexander Barkov and Peter Gulutzan
Copyright (c) 2007 by MySQL AB
All rights reserved

[ Previously published as a note on a bug report.]

MySQL offers 42 built-in collations (sets of rules
for comparison and sorting) for the Unicode character
sets utf8 and ucs2. But you can add your own.

We will describe here how to add Vietnamese Unicode
collations. This is intended as an example, so
that you can try out all the steps and then modify
based on your own rules for some other language.
We chose Vietnamse because many people asked for it
via our "Feature Request" option in bugs.mysql.com,
http://bugs.mysql.com/bug.php?id=4745.

There are two ways to add a new collation:
* Change the source code. This is the trickier way,
but it's the only way for pre-August-2007 versions.
* Change the LDML "markup" file. This hasn't been
tested much, but it's simpler, it requires no
recompilation. (LDML stands for …

# Enable some colors
alias ls="ls -G"
# Gimme details and size in KB, MB or GB, I'm not good reading bytes
alias l="ls -lh"

# SSH aliases
alias moe="ssh moe.warp.es"
# I always misspelled that one 
alias mow=moe
alias ebox="ssh root@ebox"
alias amedias="ssh amedias.org"
alias rssh="ssh -l root"

# Git alias
ci="git ci" # Formerly svn ci
# Jump to github from repository
alias github="git config -l | grep 'remote.origin.url' | sed -n \
's/remote.origin.url=git@github.com:\(.*\)\/\(.*\).git/https:\/\/github.com\/\1\/\2/p' \
| xargs open"

# MySQL
alias myserver="sudo /usr/local/mysql/support-files/mysql.server"

# Start webserver on localhost:8000 sharing current directory
alias webshare='python -c "import SimpleHTTPServer;SimpleHTTPServer.test()"'

# Rails server
alias ss="./script/server"
alias sss="screen ./script/server"
alias sr="screen -r"

AdBrite has signed off the release of my materialized view maintenance stored procedures under the GPL. LGPL is also an option, and I'm curious as to which you feel is more appropriate for a set of stored procedures that are never rendered into bytecode, or technically linked with other source. Is GPL acceptable or is LGPL more appropriate?

I am waiting on the approval of a sourceforge project to release the source code. Over the weekend I put together a series of web pages for the project, which I plan to call 'Flexviews for MySQL' which will also be hosted on sourceforge.

How often do you think about the reasons why your favorite RDBMS sucks? Last few months I was doing this quite often and yes, my favorite RDBMS is MySQL. The reason why I was thinking so because one of my recent tasks at Scribd was fixing scalability problems in documents browsing.

The problem with browsing was pretty simple to describe and as hard to fix - we have large data set which consists of a few tables with many fields with really bad selectivity (flag fields like is_deleted, is_private, etc; file_type, language_id , category_id and others). As the result of this situation it becomes really hard (if possible at all) to display documents lists like “most popular 1-10 pages PDF documents in Italian language from the category “Business” (of course, non-deleted, …

The end of May - such a lovely time of the year and a bit of a hell for each and every student. But this year it is completely different for me in the way I was selected for GSoC (omg still cannot believe I was). Anyway it is exactly one week left before the coding for GSoC 2008 starts. The right time to analyze what has been done so far and what should be done during the summer.
The first step that I took the day I was selected I started reading the MySQL documentation. No way! I let myself to relax and enjoy the life for a few days. And after that the work on the project started. And there are few things that i just have to point out. The most important one is when you start hacking into something large and new for you is a proper documentation. From this point of view MySQL documentation is just a perfect example of how things should be done. You can find almost everything related to MySQL server under …

This problem is "documented" in two bugs:
http://bugs.mysql.com/bug.php?id=36073
http://bugs.mysql.com/bug.php?id=20001

Why in the world is this just a "documentation fix"? There have been a number of occasions when I've tried to write generic stored procedures that might want to analyze information about temporary tables. For instance, given a SELECT statement, I want to determine what datatypes each select clause produces. A fairly straightforward way to do this might be to run a "create temporary table xyz as (SELECT ... LIMIT 0), to produce an empty temporary table to analyze. This doesn't work however, because there isn't any information on xyz in the information schema! Worse, SHOW statements don't work as a PREPARED STATEMENT so there isn't any way to determine this information in …