Since my first post on MySQL transaction descriptors optimization introduced in Percona Server 5.5.30-30.2 and a followup by Dimitri Kravchuk, we have received a large number of questions on why the benchmark results in both posts look rather different. We were curious as well, so we tried to answer that question by retrying benchmarks on [...]
MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
So far most of the benchmarks posted about MySQL 5.6 use the sysbench OLTP workload. I wanted to test a set of queries which, unlike sysbench, utilize joins. I also wanted an easily reproducible set of data which is more rich than the simple sysbench table. The Star Schema Benchmark (SSB) seems ideal for this. [...]
Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels
August 28, 2012 By 3 Comments
As an instructor with Percona I’m sometimes asked about the differences between the READ COMMITTED and REPEATABLE READ transaction isolation levels. There are a few differences between READ-COMMITTED and REPEATABLE-READ, and they are all related to locking.
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 [...]
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 [...]
Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
This is the third 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 targeted at the join related optimizations introduced in the optimizer. These optimizations are available in both MySQL 5.6 and MariaDB 5.5, and MariaDB 5.5 [...]
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 [...]
Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
I have been working with Peter in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by one. So in the same way this blog post is aimed at a new optimizer enhancement Index Condition Pushdown (ICP). Its available [...]
Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
Overview Profiling, analyzing and then fixing queries is likely the most oft-repeated part of a job of a DBA and one that keeps evolving, as new features are added to the application new queries pop up that need to be analyzed and fixed. And there are not too many tools out there that can make [...]
Eventual Consistency in MySQL
November 18, 2011 By 8 Comments
We’re told that foreign key constraints are the best way to enforce logical referential integrity (RI) in SQL, preventing rows from becoming orphaned. But then we learn that the enforcement of foreign keys incurs a significant performance overhead.1,2 MySQL allows us to set FOREIGN_KEY_CHECKS=0 to disable enforcement of RI when the overhead is too high. But [...]
