(Aaron Brown) A coworker came to me with a perplexing issue. He wanted to know why these two queries were not returning the same results:

(Leo Hsu and Regina Obe) I recently had the need to figure out which ranges of my keys were contiguously numbered. The related exercise is finding gaps in data as well. Reasons might be because you need to determine what data did not get copied or what records got deleted.

(Sheeri K. Cabral) We have only recently started using MySQL 5.5 here at Mozilla, and while there are features I have known about for a while, I usually hear about them early on and file them as “oh yeah, that is coming later!”.

(Bruce Momjian) I previously covered timing of queries from an external perspective. However, it is also possible to time queries internally. Each data manipulation language (dml) command (select, insert, update, delete) goes through three stages:

(Miguel Angel Nieto) There are some variables that can affect the replication behavior and sometimes cause some big troubles. In this post I’m going to talk about read_buffer_size and how this variable together with max_allowed_packet can break your replication.

(Michael Paquier) PostgreSQL 9.2 introduces a new performance feature called Index-Only scans, which was really something missing in core for performance of scan index.

(Henrik Ingo) Some time ago I finally had the chance to test the built-in load balancing feature in MySQL’s JDBC driver together with a 3 node Galera cluster. I have used this feature at a MySQL Cluster customer many years ago, so I knew it worked and I knew it was great, but I didn’t know if it wou

(Leo Hsu and Regina Obe) There is another new feature in 9.2 that doesn’t get much press, and probably because it’s hard to explain. It is a pretty useful feature if you are working with the new json type or the existing hstore type. In prior versions if you used a subquery and converted the rows to

(Andrew Morgan) The new MySQL Cluster 7.3 labs release introduces Foreign Keys to MySQL Cluster for the first time! This has been a feature requested by many, many people and has often been cited as the reason for people not being able to replace InnoDB with MySQL Cluster when they needed the extra

(Bruce Momjian) There are actually several ways you can time a query, and each has value depending on what you want to measure. You can time a query at the server (from the time it arrives until the time it completes) by setting the server parameter log_min_duration_statement = 0. However, that does