This Wednesday (March 6 at 10 a.m. PST) I’ll be presenting a webinar titled “MySQL 5.6: Advantages in a Nutshell.” In this presentation, I will provide a brief overview of the advantages MySQL 5.6 offers. My focus is a practical one – to identify the conditions in which one or another feature can be successfully [...]
Join me for ‘MySQL 5.6: Advantages in a Nutshell.’ Webinar. March 6 at 10 a.m. PST
March 4, 2013 By Leave a Comment
Write contentions on the query cache
September 5, 2012 By 5 Comments
While doing a performance audit for a customer a few weeks ago, I tried to improve the response time of their top slow query according to pt-query-digest‘s report. This query was run very frequently and had very unstable performance: during the time data was collected, response time varied from 50µs to 1s. When I ran [...]
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 [...]
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 [...]
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.
Side load may massively impact your MySQL Performance
November 13, 2011 By 7 Comments
When we’re looking at benchmarks we typically run some stable workload and we run it in isolation – nothing else is happening on the system. This is not however how things happen in real world when we have significant variance in the load and many things can be happening concurrently. It is very typical to [...]
Where does HandlerSocket really save you time?
March 16, 2011 By Leave a Comment
HandlerSocket has really generated a lot of interest because of the dual promises of ease-of-use and blazing-fast performance. The performance comes from eliminating CPU consumption. Akira Higuchi’s HandlerSocket presentation from a couple of months back had some really good profile results for libmysql versus libhsclient (starting at slide 15). Somebody in the audience at Percona [...]
Data mart or data warehouse?
July 15, 2010 By 13 Comments
This is part two in my six part series on business intelligence, with a focus on OLAP analysis. Part 1 – Intro to OLAP Identifying the differences between a data warehouse and a data mart. (this post) Introduction to MDX and the kind of SQL which a ROLAP tool must generate to answer those queries. [...]
Upgrading MySQL
January 5, 2010 By 23 Comments
Upgrading MySQL Server is a very interesting task as you can approach it with so much different “depth”. For some this is 15 minutes job for others it is many month projects. Why is that ? Performing MySQL upgrade two things should normally worry you. It is Regressions – functionality regressions when what you’ve been [...]
Unused indexes by single query
September 12, 2008 By 14 Comments
Usually unused indexes are devil, they waste diskspace, cache, they make INSERT / DELETE / UPDATE operations slower and what makes them worse – it is hard to find them. But now ( with userstatsV2.patch) you can find all unused indexes (since last restart of mysqld) by single query
1 2 3 4 5 6 | SELECT DISTINCT s.TABLE_SCHEMA, s.TABLE_NAME, s.INDEX_NAME FROM information_schema.statistics `s` LEFT JOIN information_schema.index_statistics INDXS ON (s.TABLE_SCHEMA = INDXS.TABLE_SCHEMA AND s.TABLE_NAME=INDXS.TABLE_NAME AND s.INDEX_NAME=INDXS.INDEX_NAME) WHERE INDXS.TABLE_SCHEMA IS NULL; |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | +--------------+---------------------------+-----------------+ | TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | +--------------+---------------------------+-----------------+ | art100 | article100 | ext_key | | art100 | article100 | site_id | | art100 | article100 | hash | | art100 | article100 | forum_id_2 | | art100 | article100 | published | | art100 | article100 | inserted | | art100 | article100 | site_id_2 | | art100 | author100 | PRIMARY | | art100 | author100 | site_id | ... +--------------+---------------------------+-----------------+ 1150 rows in set (1 min 44.23 sec) |
As you see query [...]
