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
Det skal for øvrigt være med kælder!
En entreprenør får bestilling på et hus. Arkitekttegningerne kommer på plads, byggeriet går igang, der er rejsegilde, og man bliver klar til aflevering. Bygherren får nøglerne og flytter straks ind, flyttebilen er der allerede. Og da flyttelæsset er på plads, kommer det fra bygherren: “Hov forresten, jeg kommer i tanke om noget: Kan I ikke… Continue reading Det skal for øvrigt være med kælder!
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
Free SSL certificates, part 2
Previously I noticed that StartSSL is offering free SSL certificates, ie. proper certificates with a CA chain that is accepted by browsers. Now while setting up my own web-server I had the opportunity to try it out. It seems to work well. The certificate seems to work, Firefox 3 does not spit out any errors… Continue reading Free SSL certificates, part 2
Hobbit monitoring
After setting up Hobbit monitoring on my home network, I discovered a curious issue with the Zyxel P-2602HW router that Fullrate delivers with their ADSL products: The Telnet administration port occasionally times-out connection attemps: I really like the Hobbit monitoring tool, I have used it ever since I heard about it when I met the… Continue reading Hobbit monitoring
Træ-algoritmer
Så er træerne plantet! Algoritmen til venstre er et espalier af palmette-typen. Det lille et-årsæbletræ (Rød Aroma, der står et Elstar ved siden af) er klippet af 10 cm oversnoren for at frembringe nye skud til foråret som skal bindes vandret ud tilhver side. Næste år klippes der over en ny snor en etager over,… Continue reading Træ-algoritmer
Garbage collection and memory leaks
So, with automatic Garbage Collection, memory leaks are a thing of the past, right? Well, not quite, of course. Automatic Garbage Collection, like most other automated programming techniques, necessarily needs to approximate (ie. guess), and while the guesses of garbage collectors are generally very good, they cannot magically predict the future. The classic way that… Continue reading Garbage collection and memory leaks
Lightning talks at Open Source Days 2008
I am giving two lightning talks at Open Source Days on October 3-4. One on improving database I/O performance using clustered indexes with MySQL/InnoDB, and one on advanced profiling with OProfile. Hope to meet up with a lot of people there!
Giv tid!
Vores røde ananas-æbler står utroligt flot her en sensommer-eftermiddag: Jeg holder meget at træer. En af grundene er, at træer tager tid. At plante et æbletræ er at planlægge mange år frem i tiden. Og ingen forventer, at et træ kan vokse op på få måneder eller år. Det giver en ro at arbejde med… Continue reading Giv tid!