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 index) is a very interesting performance optimization, a full index scan (type: index) is according to the documentation the 2nd [...]
Tools and Techniques for Index Design Webinar Questions Followup
October 4, 2012 By 5 Comments
I presented a webinar this week to give an overview of Tools and Techniques for Index Design. Even if you missed the webinar, you can register for it, and you’ll be emailed a link to the recording. I’d like to invite folks who are interested in tools for query optimization to attend the new Percona [...]
MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
I had a lot of questions on my MySQL Indexing: Best Practices Webinar (both recording and slides are available now) We had lots of questions. I did not have time to answer some and others are better answered in writing anyway. Q: One developer on our team wants to replace longish (25-30) indexed varchars with [...]
Optimizing slow web pages with mk-query-digest
April 7, 2011 By 14 Comments
I don’t use many tools in my consulting practice but for the ones I do, I try to know them as best as I can. I’ve been using mk-query-digest for almost as long as it exists but it continues to surprise me in ways I couldn’t imagine it would. This time I’d like to share [...]
Enum Fields VS Varchar VS Int + Joined table: What is Faster?
January 24, 2008 By 30 Comments
Really often in customers’ application we can see a huge tables with varchar/char fields, with small sets of possible values. These are “state”, “gender”, “status”, “weapon_type”, etc, etc. Frequently we suggest to change such fields to use ENUM column type, but is it really necessary (from performance standpoint)? In this post I’d like to present [...]
MySQL Performance – eliminating ORDER BY function
October 17, 2007 By 6 Comments
One of the first rules you would learn about MySQL Performance Optimization is to avoid using functions when comparing constants or order by. Ie use indexed_col=N is good. function(indexed_col)=N is bad because MySQL Typically will be unable to use index on the column even if function is very simple such as arithmetic operation. Same can [...]
Be careful when joining on CONCAT
October 16, 2007 By 15 Comments
The other day I had a case with an awful performance of a rather simple join. It was a join on tb1.vid = CONCAT(‘prefix-’, tb2.id) with tb1.vid – indexed varchar(100) and tb2.id – int(11) column. No matter what I did – forced it to use key, forced a different join order, it did not want [...]
Is it query which needs to be optimized ?
March 6, 2007 By 9 Comments
Last few days I had a lot of a lot of questions at MySQL Performance Forum as well as from our customers regarding query optimization… which had one thing in common – It is not query which needed to be optimized. Way too frequently people design schema first and then think how the queries they [...]
MySQL Optimizer and Innodb Primary Key
October 3, 2006 By 9 Comments
Innodb primary key is special in many senses and I was always wondering how well MySQL is integrated with Innodb to take advantage of these special features. Lets see which things work and which things do not:
Database access Optimization in Web Applications.
September 12, 2006 By 10 Comments
This is pretty simple approach I often use called to optimize web application performance if problem happens with few pages. If we have “everything is slow” problem looking at slow query logs may be better start. So what could you do ? Look at the information shown on the page which comes from database. This [...]
