Selecting rows holding group-wise maximum is a favorite problem of mine, but one which only rarely pops up. But for some reason, after my last blog post on the subject, it seems to be mentioned almost daily around here. Something that I forgot to mention in the previous post is that most of the examples… Continue reading Selecting rows holding group-wise maximum of a field, part two
Tag: mysql
Selecting rows holding group-wise maximum of a field
Today there was a question on the Freenode MySQL channel about a classical problem: Rows holding group-wise maximum of a column. This is a problem that I keep encountering every so often, so I thought I would write up something about it. A good example of the problem is a table like the following holding… Continue reading Selecting rows holding group-wise maximum of a field
Slides for my lightning talks at Open Source Days 2008
In case anyone is interested in a copy of my slides for the two lightning talks I gave at the Open Source Days 2008 conference, I have made them available here: “Optimizing Large Databases Using InnoDB Clustered Indexes:” HTML and PDF. “Profiling with OProfile and Intel Core 2 performance counters:” HTML and PDF. I waqs… Continue reading Slides for my lightning talks at Open Source Days 2008
25 years of Open Source
Today I realised that I have been programming for 25 years. Quite an anniversary! Of course, it does not really feel like that long, probably because a bit more than the first half of the time was really ‘just for fun’, as a kid’s hobby and later during University. I also realised that right from… Continue reading 25 years of Open Source
DGCov: A tool for checking test coverage of a patch
Today I published the DGCov tool on the MySQL Forge. DGCov is a neat tool that I implemented last year for use internally at MySQL, an old idea of Monty’s. The idea is to help developers to check that a new patch for the server code has received adequate testing before pushing it to the… Continue reading DGCov: A tool for checking test coverage of a patch
Partitioned archive tables
Is there anyone using partitioned archive tables in MySQL 5.1 for storing logs (or other voluminous data)? Storing large amounts of logs in a relational database can bring special challenges. Logs can take up huge amounts of space on disk, and while disk space is cheap, disk I/O can be expensive, performance-wise. But many logs… Continue reading Partitioned archive tables
Data Corruption!
At the start of this week, we suffered a corruption of our main 5.1 source code repository at MySQL. No data was lost, but I spent most of four working days on cleaning up the corruption, Monty spent one day, and many other people had to spend time on this or were stalled in their… Continue reading Data Corruption!
Full-index scan faster than full-table scan
At this years LinuxForum I wasmanning the MySQL booth together with Carsten Pedersen. We were keptquite busy with lots of people coming to tell about their use of the MySQLdatabase for their particular project and ask about or discuss a particularissue of theirs. Which was fine, since the talks did not appeal a lot to… Continue reading Full-index scan faster than full-table scan
Visual Studio limitations
MySQL 5.1 is moving to a new system for building the source code on Windows, based on CMake (more on this another time). While finishing up the last bits of this, I ran into a very annoying limitation in Visual Studio (version 7.1 I think). The library include path in Visual Studio project files (.vcproj)… Continue reading Visual Studio limitations