MySQL Can’t Use Index With Uncorrelated IN Subquery

Today is the first time I had to look at MySQL performance. Tiny database as web application back-end was having significant performance issues with spikes of CPU workload. After identifying problematic queries, I found a pile of statements using IN subqueries. I asked around and our MySQL experts assured me that this is one of the minor and not so disturbing issues, in fact. I can’t imagine what those disturbing issue are. I guess Oracle XE does have some advantages over MySQL for small installations.

Welcome Doug!

Doug Burns is finally here in Ottawa. You must see his smile in the airport – somehow he managed to read my comment and already expected me while I thought it would be surprise.

Twitter, Pythian Style… also Oracle’s SYSTEM_PRIVILEGE_MAP

To the subject at hand (psst, there will be some technical stuff in the end)… A few days ago I came across Twitter. I liked that idea very much and even tried it for one evening. I don’t think Twitter fits my lifestyle, but I recognized a very familiar concept. Indeed, it reminds me of one feature of our Pythian Support Track. Time for a bit of technical stuff…since we are mostly talking about databases on this blog, here is a view in Oracle I found very useful one day: SYSTEM_PRIVILEGE_MAP.

Oracle Gotcha: Months_between 31-days-per-month assumption

Over-the-Top Tales from the Trenches:: Bringing order to the chaos of everyday DBA life.

Do you want to know a secret? Understanding it will prevent pain and gnashing of teeth, and also leave your face comfortably free of egg. Here it is: Some Oracle functions assume there are 31 days for each month of the year! The moral of the story: be careful when using MONTHS_BETWEEN for fractional dates.

The Fine Art of Baloney Detection: In honour of Dr. Carl Sagan

Carl Sagan is a personal hero of mine. Ten years ago today this gifted communicator died of cancer. And so today the community of bloggers that loved and admired Carl Sagan is having a spontaneous blogathon in his memory. You might ask, what does Carl Sagan have to do with being a good DBA? Believe it or not, a lot. Yes, really.

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