Since I started doing the occasional consulting job for Open Query, I've seen a lot of MySQL servers that have been installed once and then forgotten about. This gave me the idea to do a short presentation about some basic MySQL server configuration. The first go was at DrupalCampMelbourne and I recently tried (and failed) to cram it into a three minute lightning talk slot at the LUV September meeting.

The title of the talk is (now) MySQL > YourSQL. I chose this not because I think that MySQL is better than the $other_database you use or because I may or may not run a newer version of MySQL on better hardware, but because I use InnoDB and …

Ref: Google: Computer memory flakier than expected (CNET DeepTech, Stephen Shankland)

Summary: According to tests at Google, it appears that today’s RAM modules have several thousand errors a year, which would be correctable if it weren’t for the fact that most of us aren’t using ECC RAM.

Previous research, such as some data from a 300-computer cluster, showed that memory modules had correctable error rates of 200 to 5,000 failures per billion hours of operation. Google, though, found the rate much higher: 25,000 to 75,000 failures per billion hours.

This is quite relevant for database servers because they write a lot rather than mainly read (desktop use). In the MySQL context, if a bit gets flipped in RAM, your data could get corrupted, or it’s ok on disk and you’re just reading corrupted data somehow. …

Innodb monitors show information about innodb internal status - which could be used for performance tuning. Lets break down the output of show engine innodb status and get a look at what is happening and how it can be improved. Just fire the "Show engine innodb status" command and check the Output.mysql> show engine innodb status\G*************************** 1. row ***************************

Firstly, I have to thank my co-workers Singer Wang and Gerry Narvaja for doing a lot of the work that resulted in this comparison.

After running both InnoDB Hot Backup and Xtrabackup, we have found that there is a measurable but not large difference between the resources that Xtrabackup and InnoDB Hot Backup consume.

Xtrabackup:

• Free
  
• takes 1.1% longer (2 min during a 3 hour backup)
  
• uses 1.4% more space (1G more in a 70G backup — this was for uncompressed backups)
  
• uses 1.115% more cpu overall
  
• split as 0.12% user, 0.66% nice, 0.025% system, …

On Monday, October 12, 2009* from 7-9 pm at MIT, I will be giving a presentation explaining SHOW ENGINE INNODB STATUS for the Boston MySQL User Group. There is information about foreign keys, transactions, deadlocks and mutexes just waiting to be discovered, and I will show how to decipher the information.

For all those in the Boston area, I hope to see you there! For those who cannot be there, we will video this presentation and make it available online, and post here when the video/slides are up.

*Yes, I realize that this is a bank holiday in the US.

We’ve been able to do MySQL 5.1 binary tarballs for a bit now (great working together with Kristian Nielsen of Monty Program), but packages are bit more tricky. Peter has been working on Debian/Ubuntu while I’ve focused on RH/CentOS. The following is from an OurDelta (trial build run) RPM install on CentOS 5 x64:

$ mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.38-maria-beta1-ourdelta (OurDelta - http://ourdelta.org/)

mysql> CREATE TABLE test.t1 (i int) ENGINE=PBXT;
Query OK, 0 rows affected (0.10 sec)

mysql> SHOW CREATE TABLE test.t1\G
*************************** 1. row ***************************
Table: test.t1
Create Table: CREATE TABLE `test.t1` (
`i` int(11) DEFAULT NULL
) ENGINE=PBXT DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> INSERT INTO test.t1 values (1);
Query OK, 1 row affected (0.03 sec)

mysql> SELECT * FROM test.t1;
+------+
| i    |
+------+
| …

This Thursday (October 1st, 14:00 UTC), Calvin Sun will give a session on InnoDB Internals: InnoDB File Formats and Source Code Structure. The InnoDB storage engine provides transactions, row-level locking, and automatic crash recovery. Its on-disk files play a pivotal role for those key features. This presentation describes how on-disk files are structured, how compressed tables are organized, and how long variable-length columns are stored. As we develop new features, it is inevitable for file format changes. We will explain how the new file format management works in the InnoDB Plugin.This talk also covers InnoDB source code structure.

For MySQL University sessions, point your browser …

MySQL backup soon becomes an important matter when the database is used in production. The pain-point comes from the fact that while backuping the database is not available to respond to client requests anymore. With mysqldump - the standard tool for performing MySQL backups - and a large database the operation can go over many tenth of minutes if not hours. If I am running my business on line this is simply not acceptable.

The classical approach to workaround this problem is to take advantage of MySQL replication. I set up a master/slave configuration where the slave acts as copy of the master. Then, when needed, I run mysqldump on the slave without any service interruption on the master.

But ZFS snapshosts bring a new straightforward approach that avoids the pain and the complexity of a master/slave replication.

Snapshots are a key feature of ZFS that allows me to save a copy of …

It is pretty understood the tables which have long rows tend to be slower than tables with short rows. I was interested to check if the row length is the only thing what matters or if number of columns we have to work with also have an important role. I was interested in peak row processing speed so I looked at full table scan in case data fits in OS cache completely. I created 3 tables - First containing single tinyint column which is almost shortest type possible (CHAR(0) could be taking less space), table with 1 tinyint column and char(99) column and table with 100 tinyint columns. The former two tables have the same row length but have number of column different 50 times. Finally I have created 4th table which is also 100 columns but one of them is VARCHAR causes raw format to be dynamic.

More specially:

PLAIN TEXT SQL:

1. CREATE TABLE `t1` (
…

This Thursday (October 1st, 14:00 UTC), Calvin Sun will give a session on InnoDB Internals: InnoDB File Formats and Source Code Structure. The InnoDB storage engine provides transactions, row-level locking, and automatic crash recovery. Its on-disk files play a pivotal role for those key features. This presentation describes how on-disk files are structured, how compressed tables are organized, and how long variable-length columns are stored. As we develop new features, it is inevitable for file format changes. We will explain how the new file format management works in the InnoDB Plugin.This talk also covers InnoDB source code structure.

For MySQL University sessions, point your browser …