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Displaying posts with tag: Programming (reset)

New algorithm for calculating 95 percentile
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The 95 percentile for query response times is and old concept; Peter and Roland blogged about it in 2008. Since then, MySQL tools have calculated the 95 percentile by collecting all values, either exactly or approximately, and returning all_values[int(number_of_values * 0.95)] (that’s an extreme simplification). But recently I asked myself*: must we save all values? The answer is no. I created a new algorithm** for calculating the 95 percentile that is faster, more accurate, and saves only 100 values.***

Firstly, my basis of comparison is the 95 percentile algo used by

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Developer Week in Review: Lion drops pre-installed MySQL
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A busy week at Casa Turner, as the infamous Home Renovations of Doom wrap up, I finish the final chapters of "Developing Enterprise iOS Applications" (buy a copy for all your friends, it's a real page turner!), pack for two weeks of vacation with the family in California (Palm Springs in August, 120 degrees, woohoo!), and celebrate both a birthday and an anniversary.



But never fear, WIR fans, I'll continue to supply the news, even as my MacBook melts in the sun and the buzzards start to circle overhead.

The law of unintended consequences

If you decide to install Lion Server, you may notice something





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NoSQL is What?
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I found myself reading NoSQL is a Premature Optimization a few minutes ago and threw up in my mouth a little. That article is so far off base that I’m not even sure where to start, so I guess I’ll go in order.

In fact, I would argue that starting with NoSQL because you think you might someday have enough traffic and scale to warrant it is a premature optimization, and as such, should be avoided by smaller and even medium sized organizations.  You will have plenty of time to switch to NoSQL as and if it becomes helpful.  Until that time, NoSQL is an expensive distraction you don’t need.

Uhm… WHAT?!

I’ve spent more than a few years using MySQL and have been using some NoSQL systems for the last year or so in a fairly busy environment. And

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Tale of a bug
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This is a tale of the bug lp:798213. The bug report has the initial report, and a summary of the real problem obtained after detailed analysis, but it does not describe the processes of getting from the former to the latter. I thought it would be interesting to document this, as the analysis of this bug was rather tricky and contains several good lessons.

Background

The bug first manifested itself as a sporadic failure in one of our random query generator tests for replication. We run this test after all MariaDB pushes in our Buildbot setup. However, this failure had only occured twice in several months, so it is clearly a very rare failure.

The first task was to try to repeat the problem and get some more data in the form of binlog files and so on. Philip kindly

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Four short links: 7 June 2011
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  • OMG Text -- a plugin for CSS framework Compass for directional text shadows. (via David Kaneda)
  • Build a Cheap Bitcoin Mine -- some day it will be revealed that the act of generating a bitcoin token is helping the Russian mafia to crack nuclear missile launch codes and Afghan druglords built the Bitcoin system to destabilize the US dollar.
  • Polycode -- a free, open-source, cross-platform framework for creative code. You can use it as a C++ API or as a standalone scripting language to get easy and simple access to accelerated 2D and 3D graphics, hardware shaders, sound and network programming, physics engines and
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    Developer Week in Review: Apple devs cry "gimme shelter"
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    Another week of industry hijinks has passed, which means it must be time for another edition of the Developer Week in Review.

    Apple offers some cover

    After developer complaints that Apple was leaving them out to dry, in regards to the Lodsys patent threats being aimed their way, the House of Jobs stepped up to the plate and announced that they considered iOS developers to be covered by the existing licenses granted to Apple by Lodsys for in-game purchases.

    This is a bit of a good-news, bad-news story from an intellectual property perspective, as it doesn't offer any relief to non-Apple developers from the patents themselves. Apple paid off Lodsys,

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    Quadrant Framework – rev7 update adds DyGraphs support
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    Quick update to the framework that was released yesterday; I’ve added automatic graph generation. I chose DyGraphs due to the quick ability to enable support – the HTML is very quick and simply loads the CSV data. It has the same zooming features of Highcharts without the JS overhead.

    Now when you run a load test you will get (in the output directory) a mixture of files: the main cumulative CSV and HTML file for the hostname that was tested, and then one CSV and HTML per report variable that was tested. This means you don’t have to drag the main CSV file into an alternate program or spend time parsing out certain variables one at a time to generate specific graphs.  I’ve also added support for limiting output of SNMP variables (LOAD,CPU,MEM). Head over here and download the update: 

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    MySQL Load Testing Framework – initial release
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    It seems that everyone loves load testing these days. Problem is that everyone is using their own quick scripts, simple or complex, to drive their tests without the ability for other DBAs to duplicate those tests. Let’s say I write a great test and share my results and graphs on the blog – you want to run the same tests to see how your new DB servers compare in performance: this framework allows you to do that without duplicating any work or writing code. This is a basic release that will get the ball rolling. I’ve included some sample tests in the README file, so give them a try.

    This codebase offers a user friendly framework for creating and visualizing MySQL database load test jobs. It is based around Sysbench, which is generally considered the industry standard load test application. The framework allows you to do the following:

      standardize your tests
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    MySQL Multiple-Column Indexes: Order Matters
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    This will just be a short reminder. If you're planning to create multiple-column indexes in MySQL, remember that the order of the columns matters. As the MySQL documentation points out, any "leftmost prefix of the index can be used." This means that the index can be used for any number of columns in a where clause as long as those columns are at the beginning of the index column list and in the same order.

    I was recently reminded of this issue while debugging a performance problem. Adding a multiple-column index resulted in query performance improvement of 400% to 2,000%. Naturally, this result is highly specific to the problem we were trying to solve.

    Developer Week in Review: Oracle sends Hudson on its way
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    Lesson for the week: If you really want to stir up an anthill, attack the conventional wisdom of code development best practices.

    In other news ...

    Another piece of Sun falls off the good ship Oracle

    At this point, I could almost follow the practice of Gregg Easterbrook 's Tuesday Morning Quarterback and put this text on Autotext, but in the past week, Oracle cast off another piece of their acquired Sun technology. In this case, it was the integrated build platform "Hudson." Either fed up with the infighting that had led to the spin-off "

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    10 Newer Entries Showing entries 31 to 40 of 246 10 Older Entries

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