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June 2012

Website Performance

A short update on the how, what and where. I got really annoyed with the website performance, so hereby a different look and feel that hopefully (trimmed and all) will provide a faster load time of pages and other material. I also introduced some caching mechanisms that hopefully will be helpful. A faster reference to

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Philosophy 17

You need to understand the application and its data.

A recent request on OTN was for advice on making this piece of SQL run faster:

delete from toc_node_rel rel
where   not exists (
                select  *
                from    toc_rel_meta meta
                where   rel.rel_id = meta.rel_id

Here’s a very short list of questions to focus the mind on possible solutions. There is a column called rel_id in both tables; columns with “id” in the name tend to be a little bit special, so are these columns:

a) the primary key of one table and foreign key to the other (if so which way round)
b) the primary keys of both tables
c) both foreign keys to a shared primary key table

Performance Efficiency – Comparing Performance Across the Stack

I started writing this post in early January this year and before it gets completely old and (maybe) uninteresting, I hereby just post it, wondering what you might think. Of course I wanted to be it the ultimate perfect braindump but I realize that I can’t get my head around all the issues anyway and

Read More… - Dynamic Sampling (III) Part I

Just a short note that the third installment's first part of the series on Dynamic Sampling has been published on

You can read there about how Dynamic Sampling deals with real-life data patterns, what about rare values and how indexes might help in such cases.


Here we go again – heading off for KScope12.

I’m sitting in the BA lounge at Heathrow waiting for the boarding call.  11 hours from now I land in Dallas, sit around for another three hours, then take off for San Anonio. It will be about 19:30 local time when I arrive, but more like 01:30 am tomorrow body-clock time.  It’s great being at these events, but I hate getting to them.

If you’re going to be there, feel free to come and say hello – my mother always warned me about talking to strangers, but that doesn’t apply any more. I’m bringing a few (hand luggage only) copies of my book to give away, so you might even want to attend one of my presentations.

Thank heavens for Time Machine…

I was running through my demos for the OTN Tour of Central America and my laptop completely died!

I ran through the disk repair utility and it found (and fixed) a number of problems, but still the laptop wouldn’t boot. Time for drastic measures!

Next I started a full restore of the hard disk from Time Machine. I left it running over night and woke up this morning to find a fully functioning laptop. :)

I’m going to record all my live demos so if something bad happens during the tour I can present from a memory stick.

Not exactly what you want the week before you go away…



Presentations now downloadable

Every now and then I am asked about the availability of the presentations I have delivered. Recently somebody asked about a presentation I delivered at the OUG Scotland about multiblock reads, and I promised to make it available. I’ve now uploaded a PDF version of all my old presentations them and put them in the ‘Whitepapers and presentation’ section.


OTN Tour of Latin America…

All the flights and hotels are booked, so it now feels very real. In a little over a week I will be taking part in the OTN Tour of Latin America.

I’m a little nervous because there are so many legs in such a short time. The tour lasts 13 days. In that time I’ll be taking 11 flights and visiting 6 locations.

  • Colombia
  • Ecuador
  • Trinidad & Tobago
  • Guatemala
  • Honduras
  • Costa Rica

I feel my stomach twisting as I look at the list. With so many locations in such a short time, the possibility of hiccups in transit seems rather high. Miss one connection and things get tricky…

I’m looking forward to meeting people, but I would be a liar if I said I’m happy about spending 2 weeks on a plane. :)



VirtualBox 4.1.18 Released…

VirtualBox 4.1.18 has been released. It’s a maintenance release and the downloads and changelogs are in the normal places.

It’s been about 2 years since I switched across to VirtualBox (when the shared virtual disks feature was introduced). In that time there have been loads of updates to the product. In the same time frame, VMware Server has had zero releases. I still get a lot of people writing to me about issues with VMware Server installations. I immediately tell them to ditch it. :)



PS. I’ve got nothing against VMware’s paid-for offerings, which do get updates. I just don’t see the point in using them when VirtualBox is free and works great for me.

Why is a Full Table Scan Selected – Will the Execution Plan Provide a Clue?

June 20, 2012 I have not had much time to respond in OTN threads recently, although I do still occasionally read threads on the forum.  I was a little surprised by one of the late responses in one of the recent threads, where one of the responders suggested actually testing the problem with the assistance of [...]