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Showing entries 1 to 12

Displaying posts with tag: query tuning (reset)

Advanced MySQL Query Tuning (Aug. 6) and MySQL 5.6 Performance Schema (Aug. 13) webinars
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I will be presenting two webinars in August:

This Wednesday’s webinar on advanced MySQL query tuning will be focused on tuning the “usual suspects”: queries with “Group By”, “Order By” and subqueries; those query types are usually perform bad in MySQL and add an additional load as MySQL may need to create a temporary table(s) or perform a filesort.

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WITHer Recursive Queries?
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Over the past few years, we’ve seen MySQL technology advance in leaps and bounds, especially when it comes to scalability. But by focusing on the internals of the storage engine for so long, MySQL has fallen behind regarding support for advanced SQL features.

SQLite, another popular open-source SQL database, just released version 3.8.3, including support for recursive SQL queries using the WITH RECURSIVE syntax, in compliance with SQL:1999.

Why is this significant? It means that MySQL is now the only widely-used SQL implementation that does not support recursive queries. Fifteen years after it was defined in the SQL standard, almost every other SQL database of note has supported this feature:

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Increasing slow query performance with the parallel query execution
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MySQL and Scaling-up (using more powerful hardware) was always a hot topic. Originally MySQL did not scale well with multiple CPUs; there were times when InnoDB performed poorer with more  CPU cores than with less CPU cores. MySQL 5.6 can scale significantly better; however there is still 1 big limitation: 1 SQL query will eventually use only 1 CPU core (no parallelism). Here is what I mean by that: let’s say we have a complex query which will need to scan million of rows and may need to create a temporary table; in this case MySQL will not be able to scan the table in multiple threads (even with partitioning) so the single query will not be faster on the more powerful server. On the contrary, a server with more slower CPUs will show worse performance

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Advanced MySQL Query Tuning: Webinar followup Q&A
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Thanks to all who attended my “MySQL Query Tuning” webinar on July 24.  If you missed it, you can you can download the slides and also watch the recorded video. Thank you for the excellent questions after the webinar as well. Query tuning is a big topic and, due to the limited time, I had to skip some material, especially some of the monitoring. I would like, however, to answer all the questions I did not get into during the webinar session.

Q: Did you reset the query cache before doing your benchmark on your query? 0.00

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New Upcoming Webinar: Advanced Query Tuning
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It is time for the Query Tuning Webinar again! This year I will be delivering the Webinar on July 24 at 10 a.m. PDT, Advanced MySQL Query Tuning, hosted by Percona. I have included some new topics about loose and tight index scan and will also show some real world examples and solutions for MySQL query optimizations.

You can register for the Webinar here. It will also be recorded, so if you can’t make it on July 24, 10am you can always watch it later.

MySQL Webinar: Advanced Query Tuning
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On July 24 at 10 a.m. PDT, I will be delivering a Webinar on Advanced MySQL Query Tuning. I will focus on optimizing the common slow queries with group by and order by. Those queries usually create temporary tables and perform a “filesort” operation. I will show how to optimize those queries so that they will be running significantly faster, which will increase the application performance and decrease MySQL load.

I presented a similar topic in April at the

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Scalability Tips & Greatest Hits
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Join 8000 others and follow Sean Hull on twitter @hullsean. In the past two years we’ve written a ton of material on scalability. Here’s the greatest hits… Why Generalists Are Better at Scaling the Web The internet stack is a complex infrastructure of interlocking components. An scalability engineer must be adept at Linux, plus webservers, […]

The post Scalability Tips & Greatest Hits appeared first on Scalable Startups.

Scalability Happiness – A Quiet Query Log
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Join 7500 others and follow Sean Hull on twitter @hullsean.

There’s a lot of talk on the web about scalability. Making web applications scale is not easy. The modern web architecture has so many moving parts. How can we grapple with the underlying problem?

Also: Why Are MySQL DBAs So Hard to Find?

The LAMP stack scales well

The truth that is half right. True there are a lot of moving parts, and a lot to setup. The internet stack made up of Linux, Apache, MySQL & PHP. LAMP as it’s called, was built to be resilient, dynamic, and scalable.

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How to Optimize MySQL UNION For High Speed
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Join 6100 others and follow Sean Hull on twitter @hullsean. There are two ways to speedup UNIONs in a MySQL database. First use UNION ALL if at all possible, and second try to push down your conditions. [mytweetlinks] 1. UNION ALL is much faster than UNION How does a UNION work? Imagine you have two [...]
Lock wait timeout on slaves
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We had a one of our slave servers frequently stop replicating with the “Innodb Lock Wait Timeout” error. The slave IO thread would continue to fetch the binlogs while the slave SQL thread kept stopping with  the above mentioned error. The teams initial inclination was to change the innodb lock wait timeout variable from 50 secs to a higher value. It was a read-only slave. Our expectation was there would be no competing writes. Then we started listing what are the next steps possible and what could be wrong.

  • There could be a user with “super” privilege in the system that was running updates directly on the slave
  • A backup script that could be locking the tables out for backup
  • Increase the “innodb lock wait timeout variable
  • Enable the innodb lock monitor
  • While we were

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    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

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    Frustration with Community vs Enteprise
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    I was working on a client’s server today to troubleshoot some variances between the result timing of some queries. Guess what I came across - the profiler is not available in certain enterprise releases but it is available on community versions of the same release number.

    I can understand if that feature was something that wasn’t fully tested in the enterprise code base and thus was only released in the community version - but if that’s the case then I don’t understand why the same version releases of Community and Enterprise can have different feature sets. That goes against the whole idea of versioning. Someone correct me if I’m wrong here but that is very frustrating.

    Showing entries 1 to 12

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