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Common MySQL traps webinar questions followup

Thanks to all attendees of the webinar yesterday! If you missed it, you can watch the video recording. Here are some questions that remained unanswered due to time constraints. Q: Are there any technical considerations …


Full table scan vs full index scan performance

Earlier this week, Cédric blogged about how easy we can get confused between a covering index and a full index scan in the EXPLAIN output. While a covering index (seen with EXPLAIN as Extra: Using …


Are You Forcing MySQL to Do Twice as Many JOINs as Necessary?

. Baron Schwartz This guest post is from our friends at Percona. They’re hosting Percona Live London from October 24-25, 2011. Percona Live is a two day summit with 100% technical sessions led by some …


Ultimate MySQL variable and status reference list

I am constantly referring to the amazing MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on variables, or look for content in the …


Impact of the sort buffer size in MySQL

The parameter sort_buffer_size is one the MySQL parameters that is far from obvious to adjust. It is a per session buffer that is allocated every time it is needed. The problem with the sort buffer …


How Percona does a MySQL Performance Audit

Our customers or prospective customers often ask us how we do a performance audit (it’s our most popular service). I thought I should write a blog post that will both answer their question, so I …


The MySQL optimizer, the OS cache, and sequential versus random I/O

In my post on estimating query completion time, I wrote about how I measured the performance on a join between a few tables in a typical star schema data warehousing scenario. In short, a query …


Managing Slave Lag with MySQL Replication

The question I often get is how far MySQL may fall behind and how to keep replication from lagging. The lag you will see will vary a lot from application to the application and from …


MySQL and PostgreSQL SpecJAppServer benchmark results

Listening to Josh Berkus presentation on OSCON today I decided to take a closer look at SpecJAppServer benchmarks results which were published by PostgreSQL recently and which as Josh Puts it “This publication shows that …


Working with large data sets in MySQL

What does working with large data sets in mySQL teach you ? Of course you have to learn a lot about query optimization, art of building summary tables and tricks of executing queries exactly as …