When executing an ALTER TABLE, InnoDB (and XtraDB) will create two InnoDB transactions: One transaction is created when the table being ALTERed is locked by the server. This will show up as something like “TABLE LOCK table `schema`.`table_name` trx id XXXX lock mode S” in SHOW ENGINE INNODB STATUS. Another is created when adding or [...]
MySQL Upgrade Webinar Questions Followup
June 28, 2012 By 7 Comments
I did a Webinar about MySQL Upgrade – Best Practices Yesterday and there were some questions we could not answer during Webinar, following Jay’s Lead I decided to post them as a Blog Post. Q: Can you go directly MySQL 5.0 to 5.5 for MyISAM tables? MyISAM have not been getting any significant development since [...]
A case for MariaDB’s Hash Joins
May 31, 2012 By Leave a Comment
MariaDB 5.3/5.5 has introduced a new join type “Hash Joins” which is an implementation of a Classic Block-based Hash Join Algorithm. In this post we will see what the Hash Join is, how it works and for what types of queries would it be the right choice. I will show the results of executing benchmarks [...]
Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
This is the second blog post in the series of blog posts leading up to the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. This blog post is aimed at the optimizer enhancement Multi Range Read (MRR). Its available in both MySQL 5.6 and MariaDB 5.5 Now let’s take a look at [...]
Benchmarks of Intel 320 SSD 600GB
February 22, 2012 By 2 Comments
I have a chance to test a system with Intel 320 SSD drives (NewRelic provided me with an access to the server), and compare performance with SAS hard drives.
The relationship between Innodb Log checkpointing and dirty Buffer pool pages
February 17, 2012 By 10 Comments
This is a time-honored topic, and there’s no shortage of articles on the topic on this blog. I wanted to write a post trying to condense and clarify those posts, as it has taken me a while to really understand this relationship. Some basic facts Most of us know that writing into Innodb updates buffer [...]
Optimizing InnoDB for creating 30,000 tables (and nothing else)
December 22, 2011 By 5 Comments
Once upon a time, it would have been considered madness to even attempt to create 30,000 tables in InnoDB. That time is now a memory. We have customers with a lot more tables than a mere 30,000. There have historically been no tests for anything near this many tables in the MySQL test suite. So, [...]
Three ways that the poor man’s profiler can hurt MySQL
December 2, 2011 By 19 Comments
Over the last few years, Domas’s technique of using GDB as a profiler has become a key tool in helping us analyze MySQL when customers are having trouble. We have our own implementation of it in Percona Toolkit (pt-pmp) and we gather GDB backtraces from pt-stalk and pt-collect. Although it’s helped us figure out a [...]
Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit
November 24, 2011 By 2 Comments
It is no secret that bugs related to multithreading–deadlocks, data races, starvations etc–have a big impact on application’s stability and are at the same time hard to find due to their nondeterministic nature. Any tool that makes finding such bugs easier, preferably before anybody is aware of their existence, is very welcome.
dbqp and Xtrabackup testing
November 16, 2011 By Leave a Comment
So I’m back from the Percona dev team’s recent meeting. While there, we spent a fair bit of time discussing Xtrabackup development. One of our challenges is that as we add richer features to the tool, we need equivalent testing capabilities. However, it seems a constant in the MySQL world that available QA tools often [...]
