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  Why are column oriented databases so much faster than row oriented databases?

I have been playing around with Hybrid Word Aligned Bitmaps for a few weeks now, and they turn out to be a rather remarkable data structure.  I believe that they are utilized extensively in modern column oriented databases such as Vertica and MonetDB. Essentially HWABs are a data structure that allows you to represent a sparse bitmap (series of 0's and 1's) really efficiently in memory.  The key trick here is the use of run length encoding to compress the bitmap into fe...

   Database,Column oriented,Speed analysis,Vertica     2012-01-29 04:27:05

  CSS Selector for Web Scraping

Creating a web scraper is no easy task. This is because it requires precision to identify the specific data points that we intend to collect for the end goal we are working towards.  Whether we are looking to create a marketing content database or analyze market trends, the last thing we need from our scraper is for it to return a lot of unnecessary data that will not help our cause. To avoid the inconvenience of going through huge amounts of data to get what we requested, it is crucial to ...

   CSS,WEB DESIGN,SELECTOR     2023-02-20 07:32:53

  One of the Best Bits of Programming Advice I ever Got

Years ago (early 1992), I attached myself to this crazy skunkworks project that was using this weird language called Smalltalk. "Object Oriented" was in its infancy as a "hot" item. High paid consultants. Lots of people laying claim to what this new object religion was all about. This was 5 years before Alan Kay would make the statement "I invented the term 'Object Oriented Programming' and this {Java and C++} is not what I had in mind."Shortly after hooking up with this whacky group with t...

   Programming advice,OOP,Smalltalk,Better design     2011-11-28 03:14:25

  The roots of Lisp

(I wrote this article to help myself understand exactly what McCarthy discovered. You don't need to know this stuff to program in Lisp, but it should be helpful to anyone who wants to understand the essence of Lisp-- both in the sense of its origins and its semantic core. The fact that it has such a core is one of Lisp's distinguishing features, and the reason why, unlike other languages, Lisp has dialects.)In 1960, John McCarthy published a remarkable paper in which he did for programming somet...

   Lips,Root,McCarthy,AI,Artificial Intelligence     2011-10-25 10:35:13

  Decision Trees in C#

Decision trees are simple predictive models which map input attributes to a target value using simple conditional rules. Trees are commonly used in problems whose solutions must be readily understandable or explainable by humans, such as in computer-aided diagnostics and credit analysis. Download source code Download sample applications Download the full Accord.NET Framework Introduction Decision Trees give a direct and intuitive way for obtaining the classification of a new instance f...

   C#,Decision tree     2012-03-23 10:00:56

  The war with spam comment

Spam comments are annoying and notorious. They are either malicious data from hackers to exploit the loopholes of the site or advertisements posted by robots. These kinds of comments have their own features and patterns, if we are careful enough, we can find ways to block most of them although it's not so easy. To block the comment with malicious executable codes such as JavaScript, we should remember one rule : never trust user input. So wherever there are user inputs, we need to check the vali...

   Spam comment,Block,Filter     2013-11-29 20:29:43

  Cool things you can do with iPhone

Nowadays smart phones have plenty of cool features you can get to know without reading the manuals. But do you know there are some useful but less well known features which can ease our life? In this post, we will share with you some cool features on iPhone. If you have an iPhone with, go and get a try. 1. Use Google Map as free GPS While traveling abroad, you can use Google Maps as a free GPS without an international data plan by making use of it's hidden offline maps feature.You can use this f...

   iPhone,Feature     2013-10-05 07:28:07

  HeartBleed: Should C be blamed for the HeartBleed bug?

There is a discussion about the security of applications written in C on Hacker News recently after the report of HeartBleed bug in OpenSSL. In this discussion, some people are saying that the applications written in C are unsafe. It seems all or most of the faults should be laid on C. I think this is biased. The language itself should not be blamed.Safety is a relative term for programming languages. No language is absolutely safe. We claim some languages like Java and C# are safer than C/C++ b...

   C,HeartBleed,Analysis,Code review     2014-04-14 03:52:55

  Fujitsu CTO: Flash is just a stopgap

Flash is a necessary waystation as we travel to a single in-memory storage architecture. That's the view from a Fujitsu chief technology officer's office. Dr Joseph Reger, CTO at Fujitsu Technology Solutions, is that office-holder, and – according to him – flash is beset with problems that will become unsolvable. He says we are seeing increases in flash density at the expense of our ability to read and write data. Each shrink in process geometry, from 3X to 2X and onto 1X, ...

   Flash,Memory,Bottleneck,Limitation,Futur     2011-08-12 07:31:34

  Rediscovering the RSync Algorithm

A:Ok, you’re synchronizing this over the web; and what do you use for the synchronization? B: Oh, we implemented the rsync algorithm. A: uhu. And what do you do with really big files? B: The same. A: And you also synchronise folders? B: Yes. A: And how do you do that? B: we iterate over the folder, using the algorithm on every file, recursing over subfolders. A: Can you try 2 things for me? First, a very large file; and second, a large codebase, and see if it holds. Introduction First ...

   ReSync algorithm,Discovery     2012-02-14 10:47:24

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