Some people believe that the ability to commit or rollback multiple statements as a single unit is a defining characteristic of the concept of transactions. They draw the -false- conclusion that enabling autocommit is the same as disabling transactions. It is easy to demonstrate why this is not true.
Autocommit
With autocommit enabled, every statement is wrapped within its own transaction. Successful execution of a statement is implicitly followed by a COMMIT, and the occurrence of an error aborts the transaction, rolling back any changes.

By default, autocommit is enabled in MySQL. You can check the current setting by executing the following statement:

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
|            1 |
+--------------+
1 row in set (0.00 sec)

The @@ prefix …

So what, if you are planning a centralized MySQL server and many clients all around the world?
First of all, check the manual
Then install timezone description tables from here
Then run a small example to see how the server and client timezones can interact.
Here is the standard server setup

mysql> show variables like 'time_zone';
+---------------+--------+
| Variable_name | Value  |
+---------------+--------+
| time_zone     | SYSTEM |
+---------------+--------+
1 row in set (0.00 sec)

Now add a table for our experiments

mysql> create table time_table (datetime_col datetime);
Query OK, 0 rows affected (0.11 sec)

Let's add some data in …

This week I helped dealing with performance problems (part MySQL related and part related to LAMP in general) of system which does quite a bit of content delivery, serving file downloads and images - something a lot of web sites need to do these days. There were quite a bit of mistakes in design for this one which I though worth to note, adding some issues seen in other systems.

Note this list applies to static content distribution, dynamic content has some of its own issues which need different treatment.

DNS TTL Settings The system was using DNS based load balancing, using something like img23.domain.com to serve some of the images. I'm not big fan of purely DNS based load balancing and HA but it works if configured well. In this case however the problem was zero TTL set in DNS configuration. This obviously adds latency especially for "aggregate" pages which may require images to be pulled from 10 different image …

I did a presentation at the MySQL miniconf as part of LCA2007 in January. It was entitled "The 10 Do's and Dont's of MySQL Cluster" and presented some of the knowledge I had learnt in setting up NDB clusters in the real world. Many people treat NDB as just a simple storage engine and can be used interchangably with InnoDB or MyISAM engine types. My talk presents some of the issues I found in simple summary form and why certain details are important when implementing a MySQL Cluster.

Most of the points will appear as common sense to seasoned DBA's and data architects, but many people currently in industry seem to get these points wrong or totally forget them. My talk exposes the problem areas, but also highlights some of the good things that were found when implementing a cluster and how it can perform better.

Pro MySQL, by Mike Kruckenberg and Jay Pipes, covers advanced MySQL topics, especially focusing on optimization and internals. I give it a solid 4 stars.

Just a small thought to share. Oracle doesn’t really comply to the rule 11 of Codd’s 12 rules. It does have database links and tables can be grouped in different locations (databases) but it’s not possible to distribute a table transparently across several locations. MySQL Cluster, on the other hand, distributes rows of a table over [...]

I will be talking about backup and recovery of Web applications at SCALE 5x. Characteristics of Web applications create unique requirements for backup and recovery. The talk will discuss open source backup and recovery tools for file systems, MySQL and PostgreSQL databases. Conference guru blog provides more information on my session.

I would be happy to meet folks who are interested in Amanda, ZRM for MySQL and open source backups in general before or after the session.

Pro MySQL, by Mike Kruckenberg and Jay Pipes, covers advanced MySQL topics, especially focusing on optimization and internals. I give it a solid 4 stars. Overview Pro MySQL covers a lot of topics you need to know, and probably will not learn about anywhere else. The book’s target audience is MySQL professionals. The authors assume significant depth of background in the subject area, and strive to put the finishing touches on your education – to take you from apprentice to journeyman, so to speak.

Continuing in my speaker spotlight series, the illustrious Jeremy Cole, famous for always having the last word at MySQL Camp, joins in the fun. Jeremy is a principal at Proven Scaling, a consulting firm focusing on scaling and replication for MySQL, but previously he worked at Yahoo! as the chief MySQL Geek and also at MySQL (oh, waaayyyy back in, what was it Jeremy? 2004?).

... from 2000 to 2004 ...

Besides being one of the most knowledgeable MySQL geeks out there — I still think we should have a MySQL Geek-off between Jeremy C and Peter Z at the conference this year... — Jeremy is also a valuable contributor to the MySQL server. Recently, Jeremy has stepped up his flow of contributions, filing patches for a SHOW PROFILE command, host cache …

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