While we always want better performance and more and larger features for MySQL, those cannot just “magically appear” from one version to another, requiring deep architecture changes and lots of lines of code. However, there are sometimes smaller features and fixes that could be implemented by an intern or an external contributor, mainly at SQL layer, and that could make the MySQL ecosystem friendlier to newbies and non-experts. Making a piece of software easier to use is sometimes overlooked, but it is incredibly important -not everybody using MySQL is a DBA, and the more people adopting it, more people will be able to live from it, both upstream and as third party providers.

Here it is my own personal list of fixes for EXPLAIN messages. If you are an experienced MySQL user you are probably aware of their meaning, but that doesn’t solve the problem for beginners. The reason why I am writing a blog post is to gather …

Since few days I was debugging a case from Yahoo! Japan team (thanks to Akira Kitada) where the query runs fine in about 0 secs with the 5.1.16 build where as the same query takes almost close to 2 minutes with the latest 5.1.22 release.

One can simply identify that this is a optimizer issue as it is not picking the right index. Lets consider the following two tables urls and urls_categories…

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| urls  | CREATE TABLE `urls` (
  `url_id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
  `url` VARBINARY(2000) NOT NULL,
  `url_status` …