I’ve started a little series on how to migrate your MySQL applications and databases over to CouchDB. Most of the process is about how you think about your data, not about the database itself, the application, or the interface to the database storage. There are some use cases for data storage that lend themselves to the CouchDB document model that provides some advantages over the table-based structure in MySQL.

The first part of the series is Moving from MySQL to CouchDB: Part 1.

Originally submitted at O’Reilly

Server bottlenecks and failures are a fact of life in any database deployment, but they don’t have to bring everything to a halt. MySQL provides several features that can protect you from outages, whether you’re running directly on the hardware, on virtual machines, or in the cloud. This…

MySQL High Availability

Good coverage of MySQL and replication

By sjmudd from Madrid, Spain on 11/24/2010 4out of 5

Pros: Easy to understand, Accurate, Well-written, Concise, Helpful examples

Best Uses: Intermediate, Expert

Describe Yourself: Sys Admin, Database Administrator

I work in quite a …

An update of MySQL from 5.0 to 5.5 on CentOS 5.5 64bit has not resulted in a good experience. The mysqld process would then crash every few minutes with the following message.

101120 8:29:27 InnoDB: Operating system error number 22 in a file operation.
InnoDB: Error number 22 means ‘Invalid argument’.
InnoDB: Some operating system error numbers are described at
InnoDB: http://dev.mysql.com/doc/refman/5.1/en/operating-system-error-codes.html
InnoDB: File name /tmpfs/#sql6cf3_5c_0.ibd
InnoDB: File operation call: ‘aio write’.
InnoDB: Cannot continue operation.

The work around was to change the tmpdir=/tmpfs (which was a 16G tmpfs filesystem) to a physical disk.

The referenced URL didn’t provide any more information of help. Unlike Bug #26662 O_DIRECT is not specified as the flush method.

One significant new feature of MySQL 5.5 is the Performance Schema. I recently performed an upgrade from 5.0 to 5.5, however my check of differences in the MySQL variables via mysqladmin variables failed because we now have a new record long variable name “performance_schema_events_waits_history_long_size”.

The full list of new performance_schema variables are:

> | performance_schema_events_waits_history_long_size | 10000                                                                                                                  |
> | performance_schema_events_waits_history_size      | 10                                                                                                                     |
> | performance_schema_max_cond_classes               | 80 …

So your not a MySQL DBA, but you have to perform like one. If you have a production environment that’s running now, what are the first things you do when it’s not running or reported as not running?

1. Are the MySQL processes running? (i.e. mysqld and mysqld_safe)
2. Can you connect locally via cli?
3. What’s in the MySQL error log?
4. What are current MySQL threads doing? Locked? long running? how many? idle sources?
5. Can you connect remotely via cli?
6. Verify free diskspace?
7. Verify system physical resources?
8. If this is a slave, is MySQL replication running? Is it up to date?
9. What is the current MySQL load, e.g. reads/writes/throughput/network/disk etc?
10. What is the current InnoDB state and load? (based on if your using InnoDB)

After you do this manually more then once you should be scripting these commands to …

Dear Kettle fans,

PDI-200 has been out there for a while now.  Jens created the feature request a little over 3 years ago.  I guess the main thing blocking this issue was not as much a technical problem but more of a licensing and dependency one (Oracle JDBC dependency and distribution license).

However, now that we have the User Defined Java Class step we can work around those pesky problems. That is because the Java code in there only gets compiled and executed at runtime so it’s perfectly fine to create any sort of dependency in there you like.

The following transformation reads a set of rows from a stored procedure as described on this web page.

In short, our UDJC step executes the following code:

begin ? := sp_get_stocks(?); …

Starting with the great work of Yoshinori-san Using MySQL as a NoSQL – A story for exceeding 750,000 qps on a commodity server and Golan Zakai who posted Installing Dena’s HandlerSocket NoSQL plugin for MySQL on Centos I configured and tested HandlerSocket under Ubuntu 10.04 64bit.

NOTE: This machine already compiles MySQL and Drizzle. You should refer to appropriate source compile instructions for necessary dependencies.

# Get Software
cd /some/path
export DIR=`pwd`
wget http://download.github.com/ahiguti-HandlerSocket-Plugin-for-MySQL-1.0.6-10-gd032ec0.tar.gz
wget http://mysql.mirror.iweb.ca/Downloads/MySQL-5.1/mysql-5.1.52.tar.gz
wget …

There are three simple practices that can improve general INSERT throughput. Each requires consideration on how the data is collected and what is acceptable data loss in a disaster.

General inserting of rows can be performed as single INSERT’s for example.

INSERT INTO table (col1, col2, col3) VALUES (?, ?, ?);
INSERT INTO table (col1, col2, col3) VALUES (?, ?, ?);
INSERT INTO table (col1, col2, col3) VALUES (?, ?, ?);

While this works, there are two scalability limitations. First is the network overhead of the back and forth of each SQL statement, the second is the synchronous nature, that is your code can not continue until your INSERT is successfully completed.

The first improvement is to use MySQL’s multi values capability with INSERT. That is you can insert multiple rows with a single INSERT statement. For example:

INSERT INTO table (col1, col2, col3) VALUES (?, ?, ?),  (?, ?, ?), (?, ?, ?);

2010 has been the first year I have re-presented any of my developed MySQL presentations. Historically I have always created new presentations, however Paul Vallee gave me some valuable advice at UC 2010. In the past two weeks I’ve traveled to seven countries in South America on the OTN LA tour where I have been speaking about and promoting MySQL.

My three current presentations have been improved and even simplified, more future improvements are planned. There is definitely a benefit in repeating a good presentation multiple times.

My SQL Idiosyncrasies That Bite OTN View more …

It's that time of the year again — the nice folks at FOSDEM have granted us a developer room at their upcoming conference (February 5+6 2011 in Brussels, Belgium)!

As usual there were more applications than they were able to accommodate, so we are very grateful for this opportunity for collaboration. Titled "MySQL and Friends", our room next year will be H.2213 with a capacity of 100 seats. It will be at our disposal on Saturday 5th, from 13:00 till 19:00. Like last year, we would like to set up a schedule of talks related to the MySQL server and the various projects that surround it. Each talk will last 20 minutes, plus 5 minutes of Q&A and a 5 minute break for switching speakers, giving us 12 slots in total to fill with …