Today I was working with application which uses Innodb and foreign keys and got into locking problems possibly due to foreign keys, so I did a little investigation on that matter.

Interesting enough it looks like most people do not think about foreign keys overhead in terms of locking. The overhead about checking referenced table is usually considered but not locking which also might be important.

So lets talk how locks seems to work with foreign keys in Innodb. I've only done a quick check so could be missing some details.

All Innodb Foreign Key related operations happen on data modification. So for example if you do SELECT FOR UPDATE on CHILD table it will not lock associated rows in PARENT table and so you can run into lock waits if you do updates to CHILD table which change parents because this is when row in PARENT table will be locked to perform update.

The checks are performed "originating" from the table …

Hi All -

I’ll pile on with Stewart and let you know that the new 5.1.14 beta is out with lots of fixes, plus other niceties for you to explore. We’ve seen a decent increase in 5.1 beta interest, with downloads of 5.1 for November experiencing over a 50% bump than what we saw in October.

In addition, I’ve been taking a sneak peek at some of our preliminary survey results (please participate!), and was interested to see that 23% of you have indicated you’re using 5.1 in production. Of course, we don’t recommend that you use 5.1 for production systems, but it’s nice to see that some of you are finding 5.1 of high enough quality to do so.

I have been working on an addition to MySQL the latest month's or so, adding XML import to MySQL. This weekend I decided that the version was good enough to submit to MySQL. You can find it at http://lists.mysql.com/internals/34169. Good enough to submit yes, probably not good enough for production, but feedback would be good.

But all in all I am quite satisfied with it.
- focus is on easy-of-use, with automatic matching of tags and attributes to field names
- support for three different xml formats: using tags for field values, using attributes or the format used by oth MySQL tools (not a good format, but anyway..)
- works very much like th CSV file load that has been a feature of MySQL for very long

I can think of some additions, like support for binary fields (probably does not work today), better handling of character encoding etc, improved handling of the SET clause etc. But then, there are …

Over at the DevZone, MySQL 5.1.14 Downloads the cool kids are grabbing the latest 5.1 beta. Lots of Cluster fixes in this release too. We’re getting to a much more polished state for NDB with each release and that’s a good thing to see.

On a totally different topic, i bought a really sweet smelling mango today and cannot wait for the right time sometime this afternoon to eat it. All the summer fruits are really nice at the moment (benefit of being in a warm December I guess) and I’m loving it.

Although 37-41 degrees (Celcius, duh) can be less fun with a rather warm laptop.

There is a much longer post I need to make on how to be productive in
writing open source software, but this is not that post.

The post is about getting projects started quickly, and distribution
of projects once you are done.

When I work on a new Apache module, its easy, I type apxs -g -n
"name" and I start coding. For perl I use h2xs to do the same thing.

But what about creating a standalone project?

I've found over time that I need to add around an hour to two, just
to create new projects. That is a waste of my time. This summer on a
train ride I started to work on a new idea and stopped myself and
instead wrote a skeleton project that I could use in the future.

Ideas don't always go anywhere. Most ideas are a few hours worth of
work that I then toss. I learn from these ideas and sometimes they
become projects. …

Last month, Paddy gave a great webinar on ZRM for MySQL. The playback is available as part of documentation in Zmanda Network, at no cost. You can register to Zmanda Network here. As a follow-up, we will be hosting a very hands on webinar on configuring ZRM for MySQL this Thursday, the 14th of Decemeber at 10.00 am PST. You can register for this webinar here.

Today, I've been given access to the Yahoo support contract with MySQL. I can now request things on Yahoo's behalf to be fixed and or added to MySQL for various versions.

This helps you because Yahoo has the same problems you might with MySQL.

This helps MySQL because to keep the product going companies need to buy support contracts or keep their support contract open.

What would you liked fixed or added?

Recently there's been several interesting blogs on the issue of open source licensing and attribution.  Let me try to summarize the discussion and see if I can highlight some areas of concern.

Historically there have been many different licenses used for open source products.  While there are not as many open source licenses as there are closed source, it has at times been confusing for users of open source to understand the subtle distinctions in the terms of different licenses.  In fact that's one of the reasons MySQL adopted the GPL license many years back. Originally, MySQL had its own open source license, but so many people were familiar with the GPL from its use on Linux, that we figured if it was good enough for Linus it was good enough for us.  We also liked the reciprocity of the GPL license since it enabled us to have a "quid pro quo" approach that enables people to use MySQL under the GPL if they are GPL and …

I often see things go past my eyes where customers (and users - i.e. those that don’t send wads of cash our way and hence are not financially supporting my beer, curry and photography habits) have amazing uptime and reliability requirements.

When talking to businesses that use MySQL, it’s not uncommon to have the “if the DB is down, our business doesn’t operate” line bandied around. How people make sure this never happens can differ (hint: it often involves replication and good sysadmin practices).

One thing I like doing is making things easier for people. Sometimes it’s also a much more complicated problem than you’re initially led to believe.

I think configuration files are obsolete. Okay, maybe just for databases. Everything should be changable as an online operation. This should also be able to be done via a standard interface - in our case, SQL. This means it’s suddenly really easy to write portable …

One thing I learned fairly early in my DBA career was that if I was ever going to excel in managing the databases under my care, I needed to do one thing: smartly automate as much of my job as I could. This became particularly important in my last full-time DBA spot where one other guy and I had responsibility for about 120 Oracle, SQL Server, and DB2 databases. A lot of these databases ran critical applications with lots of users, so we were rarely bored at work. To keep our heads above water, we needed to do something to ensure we always had our finger on the pulse of all our servers, plus we needed to make sure that any performance issue was recognized as early as possible.