One of the most typical reasons for performance and scalability problems I encounter is simply failing to do the math. And these are typically bad one because it often leads to implementing architectures which are not up for job they are intended to solve. Let me start with example to make it clear. Lets say [...]
Fix of InnoDB/XtraDB scalability of rollback segment
January 18, 2009 By 9 Comments
Recently I wrote about InnoDB scalability on 24-core box, and we made research of scalability problems in sysbench write workload (benchmark emulates intensive insert/delete queries). By our results the problem is in concurrency on rollback segment, which by default is single and all transactions are serialized accessing to segment. Fortunately InnoDB internally has mechanism to [...]
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 much space does empty Innodb table take ?
December 16, 2008 By 7 Comments
How much space would empty MyISAM table take ? Probably 8K for .frm file, 1KB for .MYI file and 0 for MYD file. .MYI file can be larger if you have many indexes. How much space will Innodb take:
Using Multiple Key Caches for MyISAM Scalability
November 26, 2008 By 8 Comments
I have written before – MyISAM Does Not Scale, or it does quite well – two main things stopping you is table locks and global mutex on the KeyCache. Table Locks are not the issue for Read Only workload and write intensive workloads can be dealt with by using with many tables but Key Cache [...]
Fighting MySQL Replication Lag
September 22, 2008 By 7 Comments
The problem of MySQL Replication unable to catch up is quite common in MySQL world and in fact I already wrote about it. There are many aspects of managing mysql replication lag such as using proper hardware and configuring it properly. In this post I will just look at couple of query design mistakes which [...]
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 [...]
How multiple disks can benefit for single client workload ?
April 26, 2008 By 4 Comments
Let us talk few more about disks. You might have read my previous post and Matt’s Reply and it looks like there are few more things to clarify and explain. Before I get to main topic of the article lets comment on IO vs Disk question. If you look at Disk Based databases all data [...]
Heikki Tuuri Innodb answers – Part I
October 26, 2007 By 19 Comments
Its almost a month since I promised Heikki Tuuri to answer Innodb Questions. Heikki is a busy man so I got answers to only some of the questions but as people still poking me about this I decided to publish the answers I have so far. Plus we may get some interesting follow up questions [...]
Implementing efficient counters with MySQL
July 1, 2007 By 16 Comments
On many web sites you would see a counter how many time given object – blog post, forum thread, image, movie etc was viewed. This is sometimes handy feature but it can be rather expensive from performance point of view. The nasty thing with counters as they are implemented the most trivial way – they [...]
