The latest from the MySQL community

I got a few questions about how to configure the cluster for disk data.
The new version of the Dimensioning Toolkit does a better job calculating:

• UNDO LOG file size
• TABLESPACE size
• UNDO Buffer size

What I write about below is taken into account in the Dimensioning Toolkit. Moreover, the things below only applies to disk data tables (read about the generic stuff about them in the reference manual).

UNDO LOG and UNDO BUFFER
Disk data tables make use of an UNDO log and an UNDO buffer.
The size of the undo log and the undo buffer is specified when you create the logfile group.

I recommend setting:

• UNDO log size = 4 to 6 times the DataMemory, thus the same size as for the REDO log.
  
• UNDO buffer size= …

To coincide with EURO 2008, I’m embarking on a virtual European tour, taking a quick look at open source policies and deployment projects in the 16 nations that are competing in the tournament.

Sweden crashed out of EURO 2008 last night a Russia qualified for the knockout stages with a well-deserved 2-0 win. As home to MySQL Sweden might be expected to be one of the more progressive adopters of open source but while there is significant interest, details of deployment projects are relatively hard to find.

Key policies:
The Swedish Agency for Public Management?s 2003 …

Not sure if the post title actually reflects the contents. 

This post describes how you can obtain the traces that MySQL server leaves behind for you if you ask it to. Once you have the traces, you can use it for:

• Debugging - It can help you to find out which source file is the server crashing, for eg.
• Learn- learn more about which functions/methods are called for a particular query by the client

Okay, so lets start.

Traceable Server

To be able to obtain traces, your server needs to be compiled with "debug" enabled. If the version information shows you something like this:

Ver 5.1.24-rc-debug for pc-linux-gnu on i686 (Source distribution)

with 'debug' appended to the version name, then you have a traceable server, else you will have to recompile it by enabling debug support:

./configure …

Not sure if the post title actually reflects the contents. 

This post describes how you can obtain the traces that MySQL server leaves behind for you if you ask it to. Once you have the traces, you can use it for:

• Debugging - It can help you to find out which source file is the server crashing, for eg.
• Learn- learn more about which functions/methods are called for a particular query by the client

Okay, so lets start.

Traceable Server

To be able to obtain traces, your server needs to be compiled with "debug" enabled. If the version information shows you something like this:

Ver 5.1.24-rc-debug for pc-linux-gnu on i686 (Source distribution)

with 'debug' appended to the version name, then you have a traceable server, else you will have to recompile it by enabling debug support:

./configure …

Few days back, one of my colleagues posted a good question. It sounds something like this;

"Temporary tables are session based that means under different sessions we can create temporary tables with similar names. Now since slave thread is singleton, how does it manage to keep them separate?"

He was very much right in asking this and the answer is not all that intuitive. Lets go through the binlog events to see why it is not that intuitive.

   1: mysql> SHOW BINLOG EVENTS IN 'log-bin.000016';

   2: . . .     

3: | log-bin.000016 |  389 | Query       | 2515922453 |         488 | use `test`; CREATE TEMPORARY TABLE test.t(a int)         |    

4: | log-bin.000016 |  488 | Query       | 2515922453 |         582 | use `test`; INSERT INTO test.t(a) VALUES(1)         |    

5: | log-bin.000016 |  582 | Query       | 2515922453 |         676 | use `test`; INSERT INTO test.t(a) VALUES(3) …

I work on the MySQL Enterprise Tools team, formerly of MySQL and now with Sun Microsystems. The 2.0 version of the Enterprise Monitor is well under way. As part of this, the Java server backend has been refactored to utilize Spring and Hibernate. Honestly, I didn't know either one of those technologies before starting this project. Oh, what a fun road it has been...

A big draw for using an off-the-shelf ORM was so that we didn't have to write our own (kind of bad and slightly wrong -- those darn transactions) caching implementations for the custom one-off ORM that existed previously. A lot of our internal meta-model is very static, so …

In MySQL, it's possible to comment out portions of code that you only want to work in specific MySQL versions:

i.e.
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `a` /*!40100 DEFAULT CHARACTER SET latin1 */;

The problem with this, is that the decimal point is omitted - and there's a real assumption that with something like 3.23.12 the "12" portion never exceeds 99.

When I look at 5.0, MySQL is currently at 5.0.60 - and there are still minor changes happening. 5.1 is at 5.1.25, and not even GA. Assuming that 5.1 does the same community/enterprise split and shuffles through releases in even numbers, how long will it take before we have 5.1.100?

If we do get there, the SQL commenting feature will need upgrading.

In MySQL, it's possible to comment out portions of code that you only want to work in specific MySQL versions:

i.e.
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `a` /*!40100 DEFAULT CHARACTER SET latin1 */;

The problem with this, is that the decimal point is omitted - and there's a real assumption that with something like 3.23.12 the "12" portion never exceeds 99.

When I look at 5.0, MySQL is currently at 5.0.60 - and there are still minor changes happening. 5.1 is at 5.1.25, and not even GA. Assuming that 5.1 does the same community/enterprise split and shuffles through releases in even numbers, how long will it take before we have 5.1.100?

If we do get there, the SQL commenting feature will need upgrading.

Sun Microsystems, Inc. today announced the general availability of MySQL™ Cluster Carrier Grade Edition 6.3, the latest version of its high-availability open source database, especially designed and certified for use in carrier grade telecom environments, such as Subscriber Data Management systems (HLR, HSS) and in Service Delivery Platforms. This new release enables Service Providers and Network Equipment Providers to deploy larger database applications and provide data availability across geographies in case of site-level failure. Additional MySQL Cluster 6.3 information and downloads are available now at www.mysql.com/cluster.

OmniMySQL 0.0.4 is a minor release fixing two bugs that I should have caught (it now crashes less). The current release can be downloaded here.