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Displaying posts with tag: explain (reset)

mk-visual-explain … visual
+4 Vote Up -0Vote Down

I love cool toys, don’t you? Especially when they help me optimize ugly, nasty, evil looking queries :)
I use mk-visual explain to help me understand better what the h*ll is happening on my MySQL servers and how they are being butchered, but today I discovered a small yet neat tool, which I think might have been overlooked. It uses mk-visual-explain, but does it visually, enabling you to open and close sections of the explain tree structure. I’m talking about http://explain.plosquare.com/.

Thank you Jan Ploski

Because Sharing is Caring

Using EXPLAIN EXTENDED / SHOW WARNINGS to Help Troubleshoot Inefficient Queries in MySQL
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When examining the execution plan of troublesome queries in MySQL, most users are aware of using EXPLAIN. However, an often overlooked, yet very helpful extension of EXPLAIN, is EXPLAIN EXTENDED coupled with the SHOW WARNINGS command.

The reason being is because it provides a little more information about how the optimizer processes the query, and thus it could help to quickly identify a problem that you might not otherwise …

  [Read more...]
MySQL’s SQL Deviations and Extensions
+3 Vote Up -1Vote Down

Today at Kaleidoscope I will be doing a 90-minute session comparing MySQL’s SQL syntax to the ANSI/ISO SQL:2003 standard, entitled What Do You Mean, “SQL Syntax Error”?

You can download the PDF slides now.

For those that may be following along the presentation later today (4 pm Eastern time), here are some links that I may throw out during the session:



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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 …

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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 …


  [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 …


  [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 …


  [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 | … Continue reading how to prevent explain from executing subqueries →

Related posts:

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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:

  1. CREATE TABLE `sales` (
  2. `id` int(11) NOT NULL AUTO_INCREMENT,
  3. `customer_id` int(11) DEFAULT NULL,
  4. `status` enum('archived','active') DEFAULT NULL,
  5. PRIMARY KEY (`id`),
  6. KEY `status` (`status`)
  7. ) ENGINE=MyISAM …
  [Read more...]
10 Newer Entries Showing entries 31 to 40 of 56 10 Older Entries

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