While preparing the webinar I will deliver this Friday, I ran into a quite interesting (although not very impacting) optimizer issue: a “SELECT *” taking half the time to execute than the same “SELECT one_indexed_column” query in MySQL 5.6.10. This turned into a really nice exercise for checking the performance and inner workings of one [...]
Be productive with the MySQL command line
December 21, 2012 By 14 Comments
Even if you are using a GUI tool to connect to your MySQL servers, one day or another, you will have to deal with the command line. So it is nice to know a few tips that can really make your work easier. Note: The commands below are only available for Unix/Linux. Using pager Most [...]
How to recover deleted rows from an InnoDB Tablespace
February 20, 2012 By 4 Comments
In my previous post I explained how it could be possible to recover, on some specific cases, a single table from a full backup in order to save time and make the recovery process more straightforward. Now the scenario is worse because we don’t have a backup or the backup restore process doesn’t work. How [...]
Shard-Query EC2 images available
May 11, 2011 By 2 Comments
Infobright and InnoDB AMI images are now available There are now demonstration AMI images for Shard-Query. Each image comes pre-loaded with the data used in the previous Shard-Query blog post. The data in the each image is split into 20 “shards”. This blog post will refer to an EC2 instances as a node from here [...]
Flexviews – part 3 – improving query performance using materialized views
April 4, 2011 By 20 Comments
Combating “data drift” In my first post in this series, I described materialized views (MVs). An MV is essentially a cached result set at one point in time. The contents of the MV will become incorrect (out of sync) when the underlying data changes. This loss of synchronization is sometimes called drift. This is conceptually [...]
Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
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 Percona documentation or forums. So I present to you what is now my newest Firefox toolbar bookmark: an option and [...]
High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
We have a lot of customers who do click analysis, site analytics, search engine marketing, online advertising, user behavior analysis, and many similar types of work. The first thing these have in common is that they’re generally some kind of loggable event. The next characteristic of a lot of these systems (real or planned) is [...]
How Percona does a MySQL Performance Audit
November 24, 2008 By 17 Comments
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 can just reply “read all about it at this URL” and share our methodology with readers a little bit. This [...]
Living with backups
November 6, 2008 By 28 Comments
Everyone does backups. Usually it’s some nightly batch job that just dumps all MySQL tables into a text file or ordinarily copies the binary files from the data directory to a safe location. Obviously both ways involve much more complex operations than it would seem by my last sentence, but it is not important right [...]
MySQL: Followup on UNION for query optimization, Query profiling
August 14, 2006 By 14 Comments
Few days ago I wrote an article about using UNION to implement loose index scan. First I should mention double IN also works same way so you do not have to use the union. So changing query to:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | mysql> SELECT sql_no_cache name FROM people WHERE age in(18,19,20) AND zip IN (12345,12346, 12347); +----------------------------------+ | name | +----------------------------------+ | ed4481336eb9adca222fd404fa15658e | | 888ba838661aff00bbbce114a2a22423 | +----------------------------------+ 2 rows in set (0.00 sec) mysql> explain SELECT sql_no_cache name FROM people WHERE age in(18,19,20) AND zip IN (12345,12346, 12347); +----+-------------+--------+-------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------+-------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | people | range | age | age | 4 | NULL | 9 | Using where | +----+-------------+--------+-------+---------------+------+---------+------+------+-------------+ 1 row in set (0.00 sec) |
So as you see there are really different types of ranges in MySQL. IN range allows [...]
