…query pattern responsible for large portion of the…on one query but yet mimics real world values distribution. The query looks something like this: SELECT * FROM table… thread to peak performance on system with 12 …JOIN::exec,mysql_sel ect,handle_select,execute_sqlcom_select,mysql_execute_command,mysql…
Post: Guidance for MySQL Optimizer Developers
September 20, 2009 By 4 Comments
…large portion of my life working on MySQL Performance Optimization and so MySQL Optimizer …on Execution Methods Performance problems can be due to optimizer picking the wrong plan, such as doing full table…join, sort merge join are all the examples of such. For me it is most important to ensure MySQL…
Post: How to find MySQL queries worth optimizing ?
September 11, 2012 By 6 Comments
… queries or queries which cause the large portion of the load on the system but how do we …is being perform but as only actual rows which are found and returned up to the top level MySQL …join 2 tables but because the access type to the tables is “const” MySQL does not count it as access to two tables…
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 23 Comments
… only 29 air carriers in the table: mysql> select count(*), count(distinct UniqueCarrier) from dim_…vastly improve the performance of queries which have to examine a large amount of…join dim_date using (date_id) GROUP BY Year) t2 ON (t.Year=t2.Year); The performance of the following queries depends on…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
… XtraDB. Requires m1.large or larger. ami-…perform on each database. To do the size comparison, I used the du utility: InnoDB file size on… 2010′; mysql> use ontime1; Database changed mysql> show table status like …table innodb-write-io-threads=4 join-buffer-size=16M key-buffer-size=64M local-infile=on…
Comment: Database problems in MySQL/PHP Applications
August 11, 2006 By 13 Comments
… however it > does not always bring good performance. Joins are expensive and > you can often do …etc. Read more in my > Why MySQL Could be slow with Large Tables article. Deciding whether or not … scanned and returned. SELECT * FROM articles INNER JOIN users ON users.id = articles.user_id AND users….
Post: MySQL VIEW as performance troublemaker
August 12, 2007 By 57 Comments
… for explain due to several layers of cascaded views built on top of one another so it is easy to write… as with subqueries and derived tables MySQL 5.0 will fail and perform very inefficiently in many counts. MySQL has two ways of handling… “join cache” is used to perform it relatively efficient, however for large derived tables it will become nightmare. So be very careful implementing MySQL VIEWs…
Post: To pack or not to pack - MyISAM Key compression
May 13, 2006 By 4 Comments
…to be treated differently. For uncompressed index blocks MySQL can do binary search inside the page – … set id=c to keep it simple: CREATE TABLE `t1` ( `id` int(10) unsigned NOT NULL , `c…than to traverse large memory areas. Reverse index scan performance got some 8 times faster and join on string …
Post: Innodb Performance Optimization Basics
November 1, 2007 By 75 Comments
… of tables though benefit of these is minor. Also make sure you wrestle OS so it would not swap out MySQL out… to use it in joins), large unpacked indexes (try to be easy on indexes). With these basic innodb performance tunings you will be better of when majority of Innodb users which take MySQL with…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
…MySQL Performance. To start with basics SHOW INNODB STATUS is command which prints out a lot of internal Innodb performance…table `test/child`: , CONSTRAINT `child_ibfk_1` FOREIGN KEY (`parent_id`) REFERENCES `parent` (`id`) ON DELETE CASCADE Trying to add in child table…large. … before joining InnoDB…
