…). I think optimizer should be fixed to always expand and use “range” lookup at least for simple ranges. Even … is traversed anyway. So how do you force MySQL optimizer to use full length in this case ? ANALYZE …A) and (A,B) for query A=Const and B>Const we can see MySQL selecting (A) index instead of…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… index lookups to one or more index range lookups. This means MySQL can employ many other optimizations like for example if columns other… made on MySQL 5.6 config: optimizer_switch=’index_condition_pushdown=off’ optimizer_switch=’mrr=on’ optimizer_switch=’mrr_cost_based=off’ optimizer_switch=’batched…_size set to 6M, the query time for MySQL 5.6 becomes approximately equal to that of MySQL 5.5. MariaDB 5.5…
Post: Joining on range? Wrong!
May 17, 2010 By 10 Comments
… around since the very beginning of MySQL, however unless you carefully analyse and profile your queries, it might easily go unnoticed. I… the date range. A very inefficient approach! MySQL was unable to optimize those simple conditions to match both product id and date range by… always comes down to removing range condition from join one way or another. For our example query this could mean introducing additional…
Post: Beware of MySQL Data Truncation
February 7, 2009 By 4 Comments
…article_id)); Query OK, 0 rows affected (0.11 sec) mysql> insert into article_comment values(4300000000,1); Query OK, … of range value adjusted for column ‘article_id’ at row 1 | +———+——+————————————————————–+ 1 row in set (0.00 sec) MySQL optimizer …
Post: How expensive is a WHERE clause in MySQL?
October 31, 2008 By 17 Comments
… much overhead does a trivial WHERE clause add to a MySQL query? To find out, I set my InnoDB buffer pool… need SQL_NO_CACHE on this query?) The average execution time for this query is 7.96, ranging from 7.65 to 8… to make your queries faster — you usually can’t optimize the WHERE clause itself, only the way that the MySQL optimizer chooses to apply…
Comment: MySQL Server Memory Usage
September 1, 2006 By 21 Comments
… ‘Com_lock_tables’, ’102′ ‘Com_optimize‘, ’0′ ‘Com_preload_keys’, ’0′… ’0′ ‘Select_full_range_join’, ’0′ ‘Select_range‘, ’5683551′ ‘Select_range_check’, ’0′…mysql.sock pid-file=/var/run/mysql/mysql.pid datadir=/db/disk2/mysql/data log-bin=/var/log/mysql/log log-slow-queries=/var/log/mysql/slow-queries…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
…index – in this case index range scan will be started and query execution stopped as soon as …indexed) Force index if needed In some cases MySQL Optimizer may prefer to use different index, which has…in slow query log as query which does not use indexes, even if it is quite fast: mysql> explain select…
Post: MySQL 6.0 vs 5.1 in TPC-H queries
March 25, 2008 By 17 Comments
…optimizer, which should affect execution plan of TPC-H queries. In reality only two queries…queries that execute slower in new MySQL 6.0 version. Query… | 1 | SIMPLE | lineitem | range …
Post: Possible optimization for sort_merge and UNION ORDER BY LIMIT
September 18, 2007 By 10 Comments
… allow MySQL to still use second portion of the index for the order by. Ranges as well as IN lists make this optimization impossible, not even speaking about index merge optimization. Lets look at… used for optimizing ORDER BY with IN. This original query (in memory data) takes 1sec. Let’s see how classic pre MySQL 5…
Page: Presentations
May 3, 2006 By
…Query Optimization Web Tuesday , Zurich, Switzerland, November 2007 Presentation covers some basic rules of queries optimization for MySQL including application based tuning such as avoiding queries…
