Shard-Query is an open source tool kit which helps improve the performance of queries against a MySQL database by distributing the work over multiple machines and/or multiple cores. This is similar to the divide and conquer approach that Hive takes in combination with Hadoop. Shard-Query applies a clever approach to parallelism which allows it to [...]
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 [...]
Tuning InnoDB Concurrency Tickets
May 24, 2010 By 5 Comments
InnoDB has an oft-unused parameter innodb_concurrency_tickets that seems widely misunderstood. From the docs: “The number of threads that can enter InnoDB concurrently is determined by the innodb_thread_concurrency variable. A thread is placed in a queue when it tries to enter InnoDB if the number of threads has already reached the concurrency limit. When a thread [...]
Joining on range? Wrong!
May 17, 2010 By 10 Comments
The problem I am going to describe is likely to be around since the very beginning of MySQL, however unless you carefully analyse and profile your queries, it might easily go unnoticed. I used it as one of the examples in our talk given at phpDay.it conference last week to demonstrate some pitfalls one may [...]
Introducing percona-patches for 5.1
February 9, 2010 By 21 Comments
Our patches for 5.0 have attracted significant interest. You can read about SecondLife’s experience here, as well as what Flickr had to say on their blog. The main improvements come in both performance gains and improvements to diagnostics (such as the improvements to the slow log output, and INDEX_STATISTICS). Despite having many requests to port [...]
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 [...]
Innodb Performance Optimization Basics
November 1, 2007 By 75 Comments
Interviewing people for our Job Openings I like to ask them a basic question – if you have a server with 16GB of RAM which will be dedicated for MySQL with large Innodb database using typical Web workload what settings you would adjust and interestingly enough most people fail to come up with anything reasonable. [...]
Redundant index is not always bad
August 28, 2007 By 7 Comments
About year ago Peter wrote about redundant indexes and mentioned sometimes it is good to leave two indexes, even one is first part of another. I’m speaking about BTREE indexes, for example, KEY (A), and KEY (A,B). From SQL point of view KEY(A) is not needed, as for queries like WHERE A=5 the index (A,B) [...]
