You can reach me with your ideas at bmurphy@paragon-cs.com . I need to see all article proposals by the 15^th of this month. Draft articles must be in by the 10^th of January, so if I accept your proposal, you have a month to get things ready. I should also mention that in the past we have used blog postings (with author permission and full credit of course). If you have blogged something recently that you feel is worthy of publishing in the magazine, send me the link and I will take a look.

Never heard of MySQL Magazine? It is a digital magazine designed for both database administrators and developers of the MySQL database server. All six back-issues are available for free download from the website.

The database system must resolve the situation where, for whatever reason, the database server stops working in the middle of a transaction.  Perhaps the power goes out, the hard drive crashes, or the CPU disappears in a cloud of smoke. Maybe the MySQL Server itself crashes for some reason. What does the MySQL Server do when operation resumes?

Potentially, there are transactions in an inconsistent state. How are inconsistent transactions resolved? They are resolved through a recovery process involving log files that are called transactional logs. There are two kinds of transactional logs: redo logs and undo logs.

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While I could spend an entire blog post—if not several—on a definition of cloud computing, I will be talking only about cloud computing in the sense of companies moving servers from their building or network operations center to running virtual servers in this computing cloud.

While there are a number of companies providing virtual servers, the most visible is Amazon, with their Amazon Web Services (AWS). I will be talking about AWS in this post as it is the service with which I am most familiar. It seems like every month, AWS rolls out new options and services. Just recently Amazon announced that you can now run on AWS the Windows operating system along with SQL Server.

Amazon also announced a service level agreement (SLA) of 99.5%. The SLA is important. It is a guarantee of service uptime. If Amazon don’t meet the SLA, then you get money back. As any of you will know, you have to be able to count on your data center. 99.5% is a pretty good level of coverage.

Beyond that, one of the new features Amazon will be implementing during the next year is the use of regions and availability zones. Regions are distinctly different areas of a country (or completely separate countries); availability zones are designed to be insulated from failures in other availability zones and provide inexpensive, low-latency network connectivity to other availability zones in the same region. What does this mean? It will soon be very easy to deploy a set of servers in different areas and/or regions so that your data and servers are spread out and not vulnerable to a single point of failure.

I am not going to go into any detail about how virtual servers work. That’s not the point of this post. I am going to concentrate on what you can do with virtual servers.

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Thanks,
Keith.

Beginning with the world of MySQL.

Monty Taylor kicks things off, bringing us news of the ability to use the innodb plugin with Drizzle. I just think its great how the Drizzle development is moving along so rapidly. My thanks to everyone involved.  Monty also puts out a call to help defray the cost of the purchase of the drizzle.org domain name.

There have been several posts this week on virtualization of MySQL Server. I point you to a colleague at Pythian, Sheeri Cabral, who wrote about some of the benefits our customers have already experienced while using virtualized servers. While virtualized servers are not a panacea, they definitely have a place in the DBA’s environment. If you don’t work with any currently, you will be doing so down the road.

The OpenSQL “unconference” is coming! The date is Nov 14 -16 in Charlottesville, Virginia, USA. Details and registration information are available here. Speaking of conferences, the MySQL Users Conference, which is in April in Santa Clara, CA, USA has extended its deadline for topic proposals.

Baron has a great post on naming conventions for your schema.

In the how-to department, Falko Timme has a good tutorial on how to set up GreenSQL to protect your databases from SQL Injection attacks. Finally, Johan Andersson has a good introductory blog post on optimizing queries for a NDB cluster, and a post on how you can get the Cluster Sandbox tool for testing the MySQL Cluster.

The Oracle world had sad news this week. Carl Backstrom, who was an Oracle employee and APEX developer, was killed early Sunday morning in a car accident in Nevada. (more…)

Recently I was working on a problem for a customer. They are converting a server with two InnoDB data files to innodb_file_per_table:

$ ls -l ibdata*
-rwxr-xr-x   1 mysql    mysql       2.0G Oct 14 13:10 ibdata1
-rwxr-xr-x   1 mysql    mysql       350G Oct 14 13:10 ibdata2

I honestly don’t recall ever seeing (or hearing about) so large a data file.

The method chosen for conversion boils down to this:

1. stop and start the server to enable innodb_file_per_table
2. alter all tables to myisam
3. stop server and delete ibdata file
4. restart server
5. convert tables back to InnoDB
6. add foreign keys

This post isn’t about how we did it, or about whether or not it was the best way, or anything like that. This post is really about the the last two steps.

There were over 500 InnoDB tables and something like 375 foreign keys. So I needed to somehow create the ALTER TABLE statements for these 500 servers. To drop the Foreign Keys, I used the following SELECT statement:

SELECT CONCAT( "mysql -u root -pPASS ", table_schema," -e 'ALTER TABLE ",table_name, ' DROP FOREIGN KEY ', constraint_name,';'' &') AS list_of_fks FROM information_schema.KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_NAME is not null ORDER BY TABLE_NAME, COLUMN_NAME;

This created a list of statements that I could then put in a batch file, edit a little, and have them run in parallel.

I used the following SELECT statement to find all InnoDB tables and prepare a command to convert them to MyISAM:

SELECT CONCAT("mysql -u root -pPASS ", TABLE_SCHEMA, " -e 'ALTER TABLE ", TABLE_NAME, " ENGINE=MYISAM;' & ") FROM INFORMATION_SCHEMA.TABLES WHERE ENGINE='INNODB';

Again, the output can be put in a batch file, modified a little, and run in parallel.

Once everything was converted to MyISAM, I shut down the database and removed the InnoDB log and data files and modified the my.cnf to so I had file_per_table and a much smaller InnoDB data file. That was the fairly straightforward part. Now the fun began. (more…)

I am not going to turn this into a rant about who is right, who is wrong, or  what should be done about it to resolve the problem. This isn’t the place. I probably don’t even have the right answer. I have a different angle.

If you are involved with MySQL as a database administrator, or if you work directly with MySQL in some other aspect, you can probably breathe a little easier. Why is this? MySQL Server has grown in market penetration for a long time. It is now a significant section of the RDBMS pie.  I predict that this market penetration will only continue to grow. As this economic downturn/recession/whatever continues, companies will look harder for ways to save money. What better way to do so than replace your proprietary RDBMS that can cost you significant amounts of money, with MySQL Server? For all intents, the same functionality is there, the speed and flexibility is certainly there, and there is a giant company behind MySQL now, providing “enterprise-ready” support.

The market is crying right now for MySQL database administrators. We don’t cost any more than Oracle or Microsoft DBAs, you know. Just a couple of years ago, very few companies hired MySQL DBAs. They hired developers who also did database administration, or a system administrators who also managed the MySQL server. Now, as the number of database servers increases and the amount of data grows they want real, honest-to-goodness database administrators. If you have production experience with MySQL server in any significant amount you will not have any problems finding a job. I don’t think this is going to change anytime soon. So, even if your company succumbs to the times, there are others out there who need your experience. Don’t be dismayed! (more…)

a) how this never should have happened in the first place.

b) how “slave drift” could be kept from happening.

c) how this is probably keeping some businesses from using MySQL.

d) how MySQL DBAs must spend thousands of hours a year wasting time fixing replication issues.

I’ll be the first person to tell you that the replication under MySQL is pretty much dead-simple to set up. My only complaint is that it is annoying to type in the two-line “CHANGE MASTER” command to set up a new slave. Even so, it makes sense.

It is also very easy, however, for a slave to end up with different data than the master server has. This can be caused by replication bugs, hardware problems, or by using non-deterministic functions. Without proper permissions, a user/developer/DBA can log into the slave server and mess the data up that way. This last is a database administrator problem, but it affects replication. There are probably other issues that astute readers will point out.

I would like to point out one common issue that would probably be categorized as a replication bug. If the master crashes for whatever reason (say, a hosting company accidentally punches the power button on a master server) it will often cause corruption of the binary log. When the master comes back up, the slave cries about a non-existent binary log position.

Possible solutions: (more…)

This post is about the announcement being made Wednesday. It seems Oracle has a surprise. A pretty well kept surprise. It’s such a big deal that Larry Ellison himself is making the announcement.

Some people, including some of my colleagues at Pythian, are speculating that this is going to be an announcement about a share-nothing clustering solution.

In the first quarter of 2007, I interviewed with a company in Atlanta, seeking my first full-time job as a MySQL database administrator. They were an online company building a social-networking website with a virtual world interface (kind of like Second Life, from what I understood). They were using an (at the time) fairly unstable version of MySQL 5.1 only because it offered clustering with the ability to store data on disk while keeping the indexes in memory. Previously, in version 5.0, everything had to be stored in-memory. Much has improved with MySQL clustering since that time.

While I don’t know for certain that Larry is going to announce in-memory clustering, I kind of hope that is what it’s all about, because it would demonstrate this: Oracle is walking a trail blazed by MySQL.

For those who don’t know, MySQL Magazine is a quarterly publication, “by the community - for the community”, free and available for download from http://www.mysqlzine.net.

Looking forward to hearing from you!