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10 Newer Entries Showing entries 31 to 40 of 53 10 Older Entries

Displaying posts with tag: explain (reset)

10x Performance Improvements in MySQL – A Case Study
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The slides for my presentation at FOSDEM 2010 are now available online at slideshare. In this presentation I describe a successful client implementation with the result of 10x performance improvements. My presentation covers monitoring, reviewing and analyzing SQL, the art of indexes, improving SQL, storage engines and caching.

The end result was a page load improvement from 700+ms load time to a a consistent 60ms.

10x Performance Improvements – A Case Study View more presentations from Ronald Bradford.
MySQL University: Optimizing Queries with EXPLAIN
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This Thursday (February 4th, 14:00 UTC), Morgan Tocker will talk about Optimizing Queries with Explain. Morgan was a technical instructor at MySQL and works for Percona today.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, and more.) All MySQL University sessions are
  [Read more...]
MySQL University: Optimizing Queries with EXPLAIN
Employee +0 Vote Up -0Vote Down

This Thursday (February 4th, 14:00 UTC), Morgan Tocker will talk about Optimizing Queries with Explain. Morgan was a technical instructor at MySQL and works for Percona today.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, and more.) All MySQL University
  [Read more...]
MySQL University: Optimizing Queries with EXPLAIN
Employee +0 Vote Up -0Vote Down

This Thursday (February 4th, 14:00 UTC), Morgan Tocker will talk about Optimizing Queries with Explain. Morgan was a technical instructor at MySQL and works for Percona today.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, and more.) All MySQL University sessions
  [Read more...]
how to prevent explain from executing subqueries
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Here’s a quick tip for using explain: You may know this already, but mysql will actually execute some subqueries when you invoke explain.  Here’s an example: mysql> explain select id from projects where id = (select max(id) from projects where name like 'en%'); +----+-------------+----------+-------+---------------+---------+---------+-------+-------+-------------+ | id | select_type | table | type | possible_keys | […] Related posts:
  • Using the ENUM data type to increase performance While going through the DATA TYPES section of the Certification...
  • YARPP powered by AdBistroPowered by
    Materialized view makes login process 25k times faster
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    It may sound like a dramatic number, and that’s because it is. One thing that is enjoyable about working on beta applications is finding new solutions and better methods to improve the user experience. The original method for displaying the recent addition of overview analytics data in the beta version of Kontrollbase was to run [...]
    How (not) to find unused indexes
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    I've seen a few people link to an INFORMATION_SCHEMA query to be able to find any indexes that have low cardinality, in an effort to find out what indexes should be removed.  This method is flawed - here's the first reason why:

    PLAIN TEXT SQL:
  • CREATE TABLE `sales` (
  • `id` int(11) NOT NULL AUTO_INCREMENT,
  • `customer_id` int(11) DEFAULT NULL,
  • `status` enum('archived','active') DEFAULT NULL,
  • PRIMARY KEY (`id`),
  • KEY `status` (`status`)
  • ) ENGINE=MyISAM AUTO_INCREMENT=65691 DEFAULT CHARSET=latin1;
  •  
  • mysql> SELECT count(*), STATUS FROM sales GROUP BY STATUS;
  • +----------+---------+
  • | count(*) | STATUS  |
  •   [Read more...]
    EXPLAIN – An essential tool for MySQL developers.
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    Just recently I came across the presentation “Bend SQL to your will with EXPLAIN” by Ligaya Turmelle via the Linked In – MySQL Speakers and Presenters group. Slides available at Slideshare. While I know a little about MySQL, I always enjoy spending time reviewing content when possible, perhaps as a good reference when asked, perhaps to glean some small point of knowledge I didn’t know, or didn’t understand completely, or had forgotten about. It’s also fun to randomly find worthwhile information.

    EXPLAIN is an essential tool for MySQL developers, if you don’t know what

      [Read more...]
    Teaching table design with EXPECT
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    The next meeting of the North Texas MySQL Users Group is next Monday and the presentation will be on designing database tables. This is part of a series for novices with MySQL and/or databases. Too often novices commit obvious sins like BIGINTs for any numeric storage field or indexing every column. EXPLAIN is a valuable tool in optimizing SELECT statements but too many DBAs do not discover it until well after they are stuck with a small, unruly group of badly designed tables.

    Using EXPLAIN is seen as a 'dark art' by too many and hopefully we can get the novices in

      [Read more...]
    Explain this
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    The EXPLAIN command is an important tool to review how a SQL query is executed and in this example includes what indexes are used.

    By adding a covering index I ended up with the following EXPLAIN plan I was unable to explain. The end result was a boost in server performance which was the ultimate goal.

    mysql> explain select max(md)  from e_r  where email = 'xxxx@gmail.com' and id = '36981';
    +----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
    | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra                        |
    +----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
    |  1 | SIMPLE      | NULL  | NULL | NULL
      [Read more...]
    10 Newer Entries Showing entries 31 to 40 of 53 10 Older Entries

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