…column from tbl WHERE pk_column IN (…) As you can see by utilizing the buffer for sorting the secondary key tuples by pk_column…in MariaDB 5.5 and not in MySQL 5.6, is that because of a bug in MySQL 5.6 code? As MRR was used in both MySQL…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 2 Comments
…by noticing the sequential access pattern. BKA is available in both MySQL 5.6 and MariaDB 5.5. You can read more about BKA in MySQL…the columns participating in the join condition and then a hash table lookup is performed, on the…the status counters. Counter Name MySQL 5.5 MySQL 5.6 MySQL…
Post: Improved InnoDB fast index creation
November 6, 2011 By 4 Comments
…in later examples I’m extending the VARCHAR column to trigger table rebuilds without affecting the table size. mysql…sorting are created in tmpdir. The constant “copying to tmp table” part will not be affected by a slow tmpdir, but rebuilding the…
Post: High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
…not null, …. primary key(day, ad) ); There are a couple of ways to handle this now. You can have the clicks column record the…by either using MySQL 5.1′s row-based replication, or in MySQL 5.0 and earlier, doing the work on a slave, then piping the…
Post: Should MySQL Extend GROUP BY Syntax ?
August 17, 2007 By 11 Comments
…sorting the data within the groups and in fact ANSI SQL even forbids you to select columns which are not aggregates or part of group by because result in this case is not defined. What would be quite helpful is to have GROUPORDER (pick the name… do not care – they are stuck enough in MySQL …
Post: How much overhead is caused by on disk temporary tables
August 16, 2007 By 26 Comments
…in set (0.00 sec) The table contains 1.000.000 rows with mostly unique “c” column. mysql…BY NULL clause as otherwise MySQL will sort the data after performing group by which is overhead we’re not…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…mysql> use ontime1; Database changed mysql> show table status like ‘ontime_fact’G *************************** 1. row *************************** Name…in the EC2 console. That the “private ip” field is selected in the list of columns to show (click show/hide to change the columns) That the…
Comment: How much overhead is caused by on disk temporary tables
August 17, 2007 By 26 Comments
… group by clause. Unfortunately, the description column is included first in the group by clause….and MySQL is determined to sort on that column (and then on name should description not be unique). So ironically, although MySQL could in…
Post: Database access Optimization in Web Applications.
September 12, 2006 By 10 Comments
… are analyzed by the query. For example SELECT COUNT(*) FROM links WHERE domain = ‘mysql.com’; … queries are GROUP BY Queries and Sort Queries – SELECT name,descr FROM titles ORDER BY rank DESC LIMIT … in single UNION (with padding to accommodate different types and number of columns) – this is not…
Post: Finding out largest tables on MySQL Server
February 4, 2008 By 24 Comments
…in MySQL 5.0+ thanks to Information Schema but I still wanted to post little query I use for the…in GB so I can save on counting zeros. The last column shows how much does the index take compared to the…
