There are many many approaches to MySQL high availability - from traditional, loosely-coupled database setups based on asynchronous replication to more modern, tightly-coupled architectures based on synchronous replication. These offer varying degrees of protection, and DBAs almost always have to choose a tradeoff between high-availability and cost. 

This is the third installment in the ‘Become a MySQL DBA’ series, and discusses the pros and cons of different approaches to high availability in MySQL. Our previous posts in the DBA series include Backup and Restore and Monitoring & Trending.

High Availability - what does it mean?

Availability is somewhat self-explanatory. If your database …

you can try to run mysql_upgrade to repair and update database medadata information. Not sure if mysql_upgrade available in mysql server 4.x or not. give it a try !!!

Relational databases are ubiquitous in OpenStack: practically every OpenStack service stores its critical metadata in a database, and the MySQL family of databases is the de-facto standard for OpenStack relational data storage. The need for high availability for these relational datastores is obvious. Galera is the default multi-master strongly-consistent replication facility for highly-available relational data in OpenStack. In this webinar, we are joined by independent OpenStack expert Florian Haas to illustrate the ins and outs of Galera for OpenStack.

Speaker bio: Florian Haas is an open source software specialist, experienced technical consultant, seasoned training instructor, and frequent public speaker. He has spoken at conferences like LinuxCon, OSCON, linux.conf.au, the OpenStack Summit, the MySQL Conference and Expo, and countless user and meetup groups across the globe.

Duration: 60 minutes

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Why A Table of Dates?

I thought it would be nice to build on the numbers table with another very useful tool.

Dates are pretty important–especially if you are playing with data warehousing. Not only dates, but all the different properties and derived goodies contained within them. You really don’t need a dates table, unless you care about efficiency and getting to all the good stuff quickly. Perhaps I’ll showcase some of the “goodies” in later posts.

Sure, most databases have built-in functions to get everything you might want. But do you really want all the inefficiency that comes with calling functions and doing calculations over and over again? I hope not. I used the method in this article when I developed a SQL Server data warehouse for a company I worked for. It was adopted by our other SQL Server guru for all the date-sensitive stuff we did (which was a lot). It increased efficiency by leaps and …

Making The Numbers Table Useful

It’s not easy to find a solution to a very simple problem in MySQL: converting a comma separated list of values into rows. Oracle database users find gobs of tutorials on using REGEXP and CONNECT BY LEVEL to make this happen. MySQL doesn’t have that. So, use the numbers table from the previous post!

The transposing is made possible by (ab)using the SUBSTRING_INDEX function. I love this function. It is right up there with GROUP_CONCAT when mixing NULL and non-null strings.

I will be using comma separated values. You can use any delimiter character you like.

Bonus: This works with empty strings, strings with one value only, and empty delimiters (i.e. “my value,,previous is empty”). No extra code needed.

Making Magic Happen

SET @mycsv = …

Percona XtraDB Cluster (PXC) has become a popular option to provide high availability for MySQL servers. However many people are still having a hard time understanding what will happen to the cluster when one or several nodes leave the cluster (gracefully or ungracefully). This is what we will clarify in this post.

Nodes leaving gracefully

Let’s assume we have a 3-node cluster and all nodes have an equal weight, which is the default.

What happens if Node1 is gracefully stopped (service mysql stop)? When shutting down, Node1 will instruct the other nodes that it is leaving the cluster. We now have a 2-node cluster and the remaining members have 2/2 = 100% of the votes. The cluster keeps running normally.

What happens now if Node2 is gracefully stopped? Same thing, Node3 knows that Node2 is no longer part of the …

This Log Buffer Edition covers various blog posts from the last week regarding Oracle, SQL Server and MySQL.

Oracle:

• Merging Overlapping Date Ranges with MATCH_RECOGNIZE
• The latest version of Enterprise Manager, EM 12.1.0.5, has been announced!
• Kdump is the Linux kernel crash-dump mechanism. In the event of a server crash, Kdump creates a memory image (vmcore) that can help in determining the cause of the crash.
• …

Why You Care About Numbers

I have worked a bit with Oracle. As such, I hang out around Oracle developers. There seems to be a common complaint among our kind when it comes to MySQL–”There aren’t any sequences!”

It never really bothered me. I wasn’t always an Oracle guy, so I didn’t always have sequences. I’m the kind of person who likes to experiment and make things happen. It just so happens there is a nice tool to help with this perceived absence: the “numbers table.”

It is really easy to set up. And, regardless of your database background, I think you will grow to love your utility.

There are multiple ways to achieve the result you want. For me, the easiest way is to work with decimal numbers. Why? Because that’s how we think. That’s pretty much standard for humans. Yeah, I know. Geeks think hexadecimal. Let’s not go there.

Without further ado, here is how you can create …

Analyzing transactional data is becoming increasingly common, especially as the data sizes and complexity increase and transactional stores are no longer to keep pace with the ever-increasing storage. Although there are many techniques available for loading data, getting effective data in real-time into your data warehouse store is a more difficult problem. VMware Continuent provides

MySQL is getting native support for JSON.  This blog post will show you how to quickly get the MySQL server with these new features running on your Windows rig and how to write a small C# program in Visual Studio 2015 that stores a JSON document using the new native JSON data type.

Schema or Schemaless

The upcoming 5.7 version of MySQL introduces a ton of new features, some of which I am quite excited about—in particular the …