… Traditionally, MySQL always uses Nested Loop Join to join two or more tables. What this means is that, select rows from first table participating… briefly explain how hash join algorithm works. Suppose you have two tables t1 and t2, that you wish to join together in….5 is slow as compared to MySQL 5.6. Next interesting thing are the last two columns of the table above and the values…
Post: MySQL-Memcached or NOSQL Tokyo Tyrant - part 1
October 15, 2009 By 16 Comments
… row in another table based on a text field ( called email address ). Seems simple enough right? My two tables each contain 5M… many clients do. Using this application I can then compare using MySQL to using MySQL + Memcached, and then to other solutions like Tokyo… a row in another table based on a text field ( called email address ). Seems simple enough right? My two tables each contain 5M…
Post: Find unused indexes
June 30, 2012 By Leave a Comment
…mysql. After some runs we can start to analyze the information on INDEX_STATISTICS table. mysql> SELECT * FROM INDEX_STATISTICS; +————–+————+————–+———–+ | TABLE_SCHEMA | TABLE…
Post: Testing MySQL column stores
August 16, 2010 By 15 Comments
… some testing on a large data set against two MySQL column-store storage engines. I’d like to … problem would be “select avg(char_column) from table” where the column contains a mix of ascii … the large data set. I compared a number of different factors between the two databases, including: Ease of …
Post: Dynamic row format for MEMORY tables
September 6, 2011 By 5 Comments
… eBay implemented true-VARCHAR support for MEMORY tables for MySQL 5.0. Although this patch did …: 25949631 (0.05% slower). VmPeak: 6267700 kB Two client threads: FRF: Insertions in 900 seconds: 42946880… very strictly, the VM Peak value is not comparable due to slightly different number of rows …
Post: Automation: A case for synchronous replication
September 19, 2012 By 2 Comments
… procedure. Lets now compare it to MySQL Replication based solution. With MySQL Replication you have …the risk with automated failover come from two elements – first failover itself involves short downtime… and development properties of familiar Innodb tables. MySQL Cluster is often a lot more …
Post: ALTER TABLE: Creating Index by Sort and Buffer Pool Size
June 27, 2012 By 4 Comments
…. I used 10mil row table which would look as following in terms of data and index size: mysql> show table status like “sbtest…) In this case we’ll see the following picture: Comparing these two graphs we can see few different observations: Buffer Pool Size…: If you’re having large tables and need to run ALTER TABLE which rebuilds the table or OPTIMIZE TABLE do not forget to enable…
Post: Three ways to know when a MySQL slave is about to start lagging
October 8, 2008 By 8 Comments
… USER_STATISTICS table. mysql> SELECT * FROM INFORMATION_SCHEMA.USER_STATISTICS WHERE USER=’#mysql_system#’\G *************************** 1. row *************************** USER: #mysql_system# …0 You can compare the BUSY_TIME to one-half the CONNECTED_TIME (because there are two replication threads …
Post: Two Types of MySQL Users
May 10, 2010 By 5 Comments
… this – you might think most relevant players in MySQL community participated in MySQL Users Conference over the years. This is about 2000… Innodb ? By the fact you can have transactions with MyISAM tables but they would not actually roll back ? Replication which can… MySQL these days. This group is often rather passive but it is a lot larger than the first one You can compare…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
… of joining two tables on a equijoin condition. So the first thing would be to designate the smallest of the two tables as the… MySQL 5.5 but takes slightly more time as compared to BKA algorithm of MySQL 5.6. Test Case C – Join a small table with a large table with a…
