Posts by Sheeri Cabral

Free and easy schema diff and patch

We are often asked to “do a schema diff and create a script that will ‘patch’ one server.”. We like to use the best tool for the job, and while diff is good, I like to use MySQL workbench. The OSS (Community) edition provides all the functionality we need for creating a schema diff and patch. MySQL workbench does both reverse engineering and “forward engineer” alter script for free in the OSS/Community version. Step by step, here’s how to do it:

There is more than one way to do it….

I spent Friday examining the systems for a more traditional consulting gig. It is a familiar story to many people — the database performance was unacceptable. The company had a few log tables that had huge amounts of inserts and foreign keys, so they used InnoDB. Unfortunately, they also used a GUID as a primary key — varchar(32) and utf8. That’s right — their primary key for many of these tables was 96 bytes long (32 characters * 3 bytes per character), and as an InnoDB table, the primary key is clustered with every other index.

Is the query cache useful?

Mark Callaghan posted a good test of the MySQL query cache in different versions. His tests clearly show that in 5.0.44 and 5.0.84 and 5.1.38, there is more query throughput when the query cache is disabled. Mark’s benchmark definitely reinforces that turning on the query cache without any knowledge of your system is a bad idea, and I agree with him on that. But it does not in any way mean that the query cache is always a bad idea. It is important to know how the MySQL query cache works, so I will first explain that, and then explain why Mark’s test is not a very good broad generalization. MySQL’s query cache is not useful all the time, but it can be quite useful!

‘Strings’ to the Rescue

A broken VIEW was caused by the view’s definer being non-existent. In this particular system, backups are done by replicating all the machines (production, development, test, etc) to one server and doing cold physical backups off that server, which currently has 12 instances running.

OpenSQLCamp 2009 presentation videos are online and free!

In record time, less than a week after the conference, all 11 videos that were taken at OpenSQLCamp Europe are online, for those who missed the sessions, or just want to relive the fun! The YouTube videos have the descriptions and resources from the official conference pages, and links to pages. If there is more information to add (for example, the slides from a talk are now online), or if you spot an error, please feel free to add a comment on the YouTube video, or as a comment to this blog post.

Video: Giuseppe Maxia Presents MySQL 5.4

At the May 2009 Boston MySQL User Group, Giuseppe Maxia of Sun Microsystems gave a presentation about MySQL 5.4 with use cases and benchmarks to show how it outperforms all other current MySQL releases (including the Google patches and the OurDelta/Percona releases). Links to the slides and video can be found here.

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