Found a nasty COALESCE() related bug in 5.5.6-rc

Seeing as it looks like 5.5 is shortly about to go GA I thought I’d give it a run and see how well it works. The only way really to test it is to give it a bit of load and look for things which break. That I did with the 5.5.6-rc community rpms, compared to the 5.1 advanced rpms I usually run.

My colleagues, Ben and Peter, found a horrible problem which means that I can’t use this even for any real usage on my real servers. See: bug#57095 for all the gory details. Thanks to them both for finding the problem and then digging down and figuring out the real cause. Sometimes developers work a long way from the database so their errors don’t translate into something I can really look at in the database. They delved into the problem and then found the cause and a nice easy test case which I could report to MySQL.

After a couple of days of running this was the only thing that turned up. It may not catch many people but it might catch you.

I hope this gets resolved quickly so I can try and find the next bug. 5.5 does look interesting and I’m looking forward to it becoming GA. Once that happens I have to decide the upgrade plan again.  That is a surprisingly long procedure to run from start to finish. I do not want to chase MySQL and it’s newest release but performance changes in 5.5 make it very interesting. I remember when I tested 5.4 last year it was clear that 5.4 was much better than 5.1 performancewise, but it was not GA. Had I jumped on the 5.4 bandwagon to get these extra features or speed I would probably have paid for that. So it does pay to be patient.

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