In the next week, I'll be interviewing Paul McCullagh, the architect behind the PBXT storage engine. If you have any questions for Paul, please post them here by Monday 16th November.

Note: The idea for this interview was inspired by a previous interview with Heikki Tuuri - creator of InnoDB. You can see the answers here and here.

Entry posted by Morgan Tocker | …

Answering questions asked on the site.

Maxym asks:

Inverting date ranges is an interesting article.

I had the same problem, and I solved it almost the same way in PostgreSQL. Your solution is great! The problem is to implement it on MySQL :) And of course performance there.

Do you have any idea how to transform this query for MySQL?

The query in question regards inverting contiguous non-overlapping date ranges: transforming them so the the gaps become the ranges and the ranges become the gaps.

The following set:

Usually, it's a bad idea to allow elements in a tree to be parents of themselves, because that creates problems with trying to add other children to those elements, or even listing out the tree's structure.But, sometimes things have to be their own parent. For example, if you want to report details of an element's children to the parent element, what happens at the top level of the tree? You can't outright exclude a tree element from the reporting, you can't create a placeholder element because that would skew the tree, and you can't add in a special case in your code base for that single item.Well, you could, but you don't want to. You'd rather have a simple and elegant solution that doesn't require lots of special cases for tree levels, and that doesn't require maintenance. So what do you do? ...

Here is a quick way to compile a simple MGM API application. The example will get the state of all nodes in MySQL Cluster and print whether they are connected or not.

All this without a Makefile, we just want to have some simple example on Linux to see how it works. It's basic, maybe, but sometimes useful to just have a peek.

Requirements! We assume that:

1. you installed MySQL Cluster 6.3 or higher, preferably under /usr/local/mysql,
2. your cluster is up and shiny,
3. and ndb_mgmd runs on the same machine you are compiling the MGM API test application on.

The code, save it in a file called mgmapi_test.cc …

MySQL Cluster 6.3.28b and 7.0.9b contain optmizations which can greatly reduce the time taken for data nodes to restart – this includes restarting a single node, performing a rolling restart or a full system restart.

The benefits you see will depend on many factors including including the size of your database and the frequency, size and complexity of your transactions. As an experiment, I re-ran some data node restart timings from an earlier post (http://www.clusterdb.com/mysql-cluster/mysql-cluster-data-node-restart-times/)

The headline figure from my results is that for a 6 Gbyte database, with modest traffic I saw a 2.2x improvement. This is using very simple transactions and so you may get a much better improvement – 70x is being seen by some!!! The best news is that the slower your …

As a developer you’re probably using a versioning control system, like subversion or git, to safeguard your data. Advantages of using a VCS are that you can walk to the individual changes for a document, see who made each change and revert back to specific revision if needed. These are features which would also be nice for data stored in a database. With the use of triggers we can implement versioning for data stored in a MySQL db.

The revisioning table
We will not store the different versions of the records in the original table. We want this solution to be in the database layer instead of putting all the logic in the application layer. Instead we’ll create a new table, which stores all the different versions and lives next to the original table, which only contains the current version of each record. This revisioning table …

MySQL Connector/Net 6.0.5, a new version of the all-managed .NET driver
for MySQL has been released. This is a maintenance release and is approved for use
in all situations.

It is now available in source and binary form from
[http://dev.mysql.com/downloads/connector/net/6.0.html] and mirror sites
(note that not all mirror sites may be up to date at this point of time
- if you can't find this version on some mirror, please try again later
or choose another download site.)

There are lots of bug fixes in this release so please review the change log.

Thank you!

The binary version for MySQL Cluster 6.3.27a has now been made available at http://dev.mysql.com/downloads/select.php?id=14&display=current&previous_ga=1#downloads

A description of all of the changes (fixes) that have gone into MySQL Cluster 6.3.27a (compared to 6.3.26) can be found in the MySQL Cluster 6.3.27a Change Log.

Since the European Commission announced it was opening an in-depth investigation into the proposed takeover of Sun Microsystems by Oracle with a focus on MySQL there has been no shortage of opinion written about Oracle’s impending ownership of MySQL and its impact on MySQL users and commercial partners, as well as MySQL’s business model, dual licensing and the GPL.

In order to try and bring some order to the conversation, we have brought together some of the most referenced blog posts and news stories in chronological order.

Part one took us from the announcement of the EC’s in-depth investigation up to the eve of the communication of the EC’s Statement of Objections.

Part two, below, takes us from there to the eve of the announcement of Oracle’s concessions. …

This is part 3 of my Tyrant extra's, part 1 focused on durability, part 2 focused on the perceived performance wall.

#3.  Tokyo Cabinet Can have only a single writer thread, bottlenecking performance

When writing an application using Tokyo Cabinet only one connection can be opened as a “writer”  while the rest are readers.  Tyrant allows for multiple “writes”  to be sent in from multiple applications but it still single threads them when writing out to disk.   If you run several threads all just inserting into Tyrant your will see tyrant hit 100% Cpu on 1 core, and your writes will start to peter out quickly.

In my tests when I was not disk bound (FS Cache writes) I was able to complete 4Million inserts in a little over 91 seconds using 8 threads.  I actually averaged 43896.98 inserts per second during my 8 thread test.  Moving to 10 threads doing the same 4Million inserts I …