It's been some time since I last wrote an overview of the state of the MySQL forks, but the last few weeks have been eventful enough that it is a good time to again see how the competing variants are positioned against each other.

I have written on this topic 1-2 times a year. Here are links to the previous overviews:

Map of MySQL forks and branches (2010)
The state of MySQL forks: co-operating without co-operating (2010)
Observations on Drizzle and PostgreSQL
Percona.tv: …

Synchronous data replication over long distances has the sort of seductive appeal that often characterizes bad ideas.  Why wouldn't you want every local credit card transaction simultaneously stored on the other side of the planet far away from earthquake, storms and human foolishness?  The answer is simple: conventional SQL applications interact poorly with synchronous replication over wide area networks (WANs).

I spent a couple of years down the synchronous replication rabbit hole in an earlier Continuent product.  It was one of those experiences that make you a sadder but wiser person.  This article digs into some of the problems with synchronous replication and shows why another approach, asynchronous multi-master replication, is currently a better way to manage databases connected by long-haul networks.

Synchronous Replication between …

Just for the pure insane fun of it, I accepted the challenge of “what can you do with the text format of the schedule?” for BarCampMel. I’m a database guy, so I wanted to load it into a database (which would be Drizzle), and I wanted it to be easy to keep it up to date (this is an unconference after all).

So… the text file itself isn’t in any standard format, so I’d have to parse it. I’m lazy and didn’t want to leave the comfort of the database. Luckily, inside Drizzle, we have a js plugin that lets you execute arbitrary JavaScript. Parsing solved. I needed to get the program and luckily we have the http_functions plugin that uses libcurl to allow us to perform HTTP GET requests. I also wanted it in a table so I could query it when not online, so I needed to load the data. Luckily, in Drizzle we have the built in EXECUTE functionality, so I could just use the JavaScript to parse the response from the HTTP GET request and …

For Drizzle and for all of the projects we work on at Percona we use the Bazaar revision control system (largely because it’s what we were using at MySQL and it’s what MySQL still uses). We also use Jenkins.

We have a lot of jobs in our Jenkins. A lot. We build upstream MySQL 5.1, 5.5 and 5.6, Percona Server 5.1, Percona Server 5.5, XtraBackup 1.6, 2.0 and 2.1. For each of these we also have the normal trunk builds as well as parameterised ones that allow a developer to test out a tree before they ask for it to be merged. We also have each of these products across seven operating systems and for each of those both x86 32bit and 64bit. If we weren’t already in the hundreds of jobs, we certainly are once you multiply out between release and debug and XtraBackup being across so many MySQL and Percona …

I have a friend who is fond of telling a story from way back in November 2008 at the OpenSQL camp in Charlottesville, Virgina. This was relatively shortly after we had announced to the public that we’d started something called Drizzle (we did that at OSCON) and was even closer to the date I started working on Drizzle full time (which was November 1st). Compared to what it is now, the Drizzle code base was in its infancy. One of the things we hadn’t yet sorted out was the rewrite of the replication code.

So, I had my laptop plugged into a projector, and somebody suggested opening up some random source file… so I did. It was a bit of the replication code that we’d inherited from MySQL. Immediately we spotted a bug. In fact, between myself and Brian I think we worked out that none of the error …

Taxonomy of Database Tools

In the MySQL ecosphere there is an ecosystem of tools.  Like real-world ecosystems, the “creatures” in the MySQL tools ecosystem can be classified and organized by a taxonomy.  There are already multiple taxonomies of software bugs (e.g. A Taxonomy of Bugs), but as far as I know this is the first Taxonomy of Database Tools.  A taxonomy of database tools serves useful purposes, as discussed in the previously linked page.  For me, the most useful purpose is the high-level ecosystem view which I use to compare MySQL tools to  …

A few weeks ago I blogged about the HTTP JSON api in Drizzle. (See also a small demo app using it.) In this post I want to elaborate a little on the design decisions taken. (One reason to do this is to provide a foundation for future work, especially in the form of a GSoC project.)

Looking around: MongoDB, CouchDB, Metabase

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This is the second and final part of my notes from the MySQL conference. In this part I'll focus on the technical substance of talks I saw, and didn't see.

More than ever before I was a contributor rather than attendee at this conference. Looking back, this resulted in seeing less talks than I would have wanted to, since I was speaking or preparing to speak myself. Sometimes it was worse than speaking, for instance I spent half a day picking up pewter goblets from an egnravings shop... (congratulations to all the winners again :-) Luckily, I can make up for some of that by going back and browse their slides. This is especially important whenever 2 good talks are scheduled in the same slot, or in the same slot when I was to speak. So I have categorized topics here along various axes, but also along the "things I did see" versus "things I missed" axis.

My own talks

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I have finally recovered from my trip to Santa Clara enough that I can scribble down some notes from this year's MySQL Conference. Writing a travel report is part of the deal where my employer covers the travel expense, so even if many people have written about the conference, I need to do it too. And judging from the many posts for instance from Pythian's direction, Nokia is perhaps not the only company with such a policy?

Baron's keynote

There has usually always been something that can be called a "soft keynote". Pirate Party founder Rick Falckvinge speaking at a database conference is a memorable example (I still keep in touch with him, having met him at the Hyatt Santa Clara). This year there was one less day, and therefore less keynotes. The soft keynote was therefore taken care of by Baron using some time out of Peter's opening keynote. Baron's talk was an ode to the conference itself, underscoring the meaning of the …

Since the famous conjecture by Eric Brewer and proof by Nancy Lynch et al., CAP has given the world countless learned discussions about distributed systems and many a well-funded start-up.  Yet who truly understands what CAP means?  Even a cursory survey of the blogosphere shows profound disagreement about the meaning of terms like CP, AP, and CA in real systems.  Those who disagree on CAP include some of the most illustrious personages of the database community.

We can therefore state with some confidence that CAP is confusing. Yet this observation itself raises deeper questions.  Is CAP merely confusing?  Or is it the case that as with other initially accepted but now doubtful ideas like the Copernican …