Monday, October 21, 2013

FAQ: InnoDB extended secondary keys

MySQL 5.6 introduced a new feature called extended secondary keys. We get a lot of questions about it and find that most of them come from a few incorrect assumption. In this post I'll try to get rid of the confusion once and for all. Famous last words... here goes:

Q1: Do I need to do anything to enable extended secondary keys?

No, nothing at all. It's on by default and I can't see any sensible reason why you would want to disable it. However, it is possible to disable it by tuning the optimizer_switch: SET optimizer_switch='use_index_extensions={on|off}'.

Q2: Does extended secondary keys only work with InnoDB?

No, it should work with any storage engine that uses the primary key columns as reference to the row, which means most storage engines with clustered primary keys. I say "should" because it requires a minimum of work from the storage engine provider; it must announce to MySQL that it is supported.

Friday, October 18, 2013

The second MySQL seminar: a summary

Once again, Geir Høydalsvik and I had the pleasure of hosting a MySQL mini-seminar in Trondheim. 25+ attendants from at least 7 different companies and a few professors from the computer science dept. at NTNU showed up on yesterdays event. I recognized many of these from the first seminar but there were some new faces as well.

This time, Mark Leith came on a visit from the UK. He gave an introduction to Performance Schema and ps_helper. ps_helper is a really nice tool to make sense of the overwhelming amount of data collected by PS. He also gave a very convincing demo of MySQL Enterprise Monitor (MEM). More than a few attendants now plan to give MEM a try in their environment. You can too - there's a 30 day trial, which should be more than enough to decide if you need it :-)

Like last time, we had great discussions, pizza and a very good time. I'm looking forward to the next seminar already.

If you're interested, Mark's PS presentation can be found on slideshare. ps_helper is both on github and on his blog. ps_helper comes highly recommended!