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Oracle and postgres disk IO performance

This post is about one of the fundamentally important properties of a database: how IO is done. The test case I studied is doing a simple full table scan of a single large table. In both Oracle and postgres the table doesn’t have any indexes or constraints, which is not a realistic example, but this doesn’t change the principal topic of the study: doing a table scan.

I used a publicly available dataset from the US bureau of transportation statistics called
The zipped file is 347MB, unzipped size 1.7GB.

Daylight Saving Time Causes Performance Issues!

Since I’m starting employment with Pythian on Monday, this is the last technical post that is exclusive to this blog. Future technical tips, discoveries and stories will appear on the Pythian blog, and either copied here or linked to from here. BTW. I already made my first post in the Pythian blog today, as the editor of the Log Buffer – and I’m not even an employee yet :)

So, lets end this with a bang. Real life story on how Daylight Saving Time caused one query to take twice as long as before! And its not even an April Fools joke :)