Developers Club geek daily blog

Emulation of safety of lines in PostgreSQL 9.4

11 months, 3 weeks ago
In PostgreSQL 9.5 declarative safety of lines will appear. You can set rules for tables and make their execution automatic, for example, allowing the user of joe to see only lines which in the field of owner have a joe value.

It is the excellent tool and it had to appear for a long time. It it was not made in PostgreSQL 9.4, but made by means of automatically updated representations of security_barrier. They and the LEAKPROOF functions create the base on which safety of lines is constructed. You can use these components without support of declarative policy for achievement of safety of lines in 9.4.

Earlier I already discussed representation security_barrier. This post comprises examples of how there can be an information leakage from representation and as security_barrier of representation prevent such leaks. I will assume that you are familiar with the principles stated in the rest of article and I will repeatedly not stage demonstration of how there are information leakages from representations, etc.

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Birthday of the founder of the oldest hacker club Chaos Computer Club

11 months, 3 weeks ago


On December 20, 1951 Herwart Holland-Moritz famous as Wow Holland (Wau Holland), the co-founder of Chaos Computer Club (CCC) in 1981 was born, is one of the hacker clubs, oldest in the world.

imageCCC gained the world fame when his members published vulnerabilities in a security system of the German teletext operator Bildschirmtext (Btx). Hackers received 134 000 DM from bank, repeatedly getting access to its page to Btx. In several days hackers returned money.

Wow Holland was a brilliant speaker, the person with the big sense of humour standing on positions of openness and freedom of information exchange.

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Russian AI Cup: the best programmers of artificial intelligence are selected

11 months, 4 weeks ago


On December 13 the final of the fourth annual championship on programming of artificial intelligence of Russian AI Cup came to the end. This time the skill was shown by over 1 600 programmers creating artificial intelligence for driving in races on a survival.

Under the terms of the championship it was possible to use one of languages: C ++, Java, C#, Python, Ruby or Pascal. After a series of intense competitions in the final 50 strongest were beaten out. And by results of last "race" the gold prize was won by Alexander "santa324" Santalov from Moscow. As an award he received MacBook Pro. Anton "Angor" Gordiyenko got "silver" and "bronze" from Moscow and to Yury "SDil" Semyonov from St. Petersburg, they were awarded by MacBook Air ultrabooks. Were not left without prizes and the contestants who took with fourth on the sixth places were handed to them iPad Air 2 tablets. We congratulate Denis "ud1" Utkin, Sergey "SKolotienko" Kolotiyenko and Sergey "Karkun" Ivanov! However to other participants still early to relax, and early to sum up of us adjusted totals of the championship. A week more of competitions in the Sandbox is necessary, and on their results the best 6 participants will win incentive prizes from partners of action.

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We pass from STM32 to the Russian K1986BE92QI microcontroller. Practical application: We poll keys, we manage the LED brightness (we generate tension on an output) by means of PWM (PWM+TIM+PORT)

1 year ago

Introduction.

In two previous articles we generated a clock signal of the frequency necessary to us by means of PWM, receiving on a LED equal intervals of a luminescence and its absence. This task takes place to be in practice (in one of the subsequent articles we will precisely face it). But most often PWM is used for other designated purpose. One of the most widespread — management of brightness of LEDs or the rotational speed of motors. Also by means of PWM it is possible to generate a sound (about what there will be following article). And in this article I would like to tell how on our controller it is possible to implement management of LED brightness.

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Reefs of backup and recovery of deduplitsirovanny data in the scenario disaster recovery

1 year ago


Developing a subject of a backup and recovery on SHD with new architecture, we will consider nuances of work with deduplitsirovanny data in the scenario disaster recovery where SHD with own deduplication are protected, namely as this technology of effective storage can help or prevent to recover data.

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The first steps about Java 9 and the Jigsaw project – part second

12 months ago
Hello, Habr.

After some delay we publish the second part of article about the Jigsaw and Java 9 project which left in the blog Codecentric. Transfer of the first part is here.

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John Horton Conway: Life as game — the termination

11 months, 2 weeks ago
first part

Having arrived home, Gardner immediately showed to Conway more than 20 articles devoted to calculation of a day of the week for any date. Lewis Carroll's rule looked better than the others. Gardner turned to Conway and told: "John, you need to develop simpler rule which I will be able to share with readers". And, as Conway, long winter nights when Mr. and Mrs. Gardner went to sleep at home (though on a visit he came to them only in the summer) tells, Conway reflected how to make such calculation rather simple that it could be explained to the average any passer-by.

He thought over it all way home, and in the general room of university, and at last guessed "the rule of the Doomsday". For work only addition, subtraction and storing were required for algorithm. Also Conway thought up the mnemonic rule helping to store intermediate calculations on hand fingers. And for the best storing of information on date, Conway bites the thumb.

Traces from teeth have to be visible! Only this way it is possible to remember it. When I tell students about this method, I always ask someone from the first row to confirm existence of marks from teeth in a finger. Serious people so you will not force to do – they will decide that it is kindergarten. But sense that all this business usually is not delayed at you in a brain and you forget the date of birthday designated to you by the person. But the thumb is capable to remember for you how far this date will be spaced from next "Doomsday".


Over the years Conway taught this algorithm thousands of people. Sometimes in a conference room the person on 600, calculating birthdays of each other and biting the thumbs is taken. And Conway, as always, tries to be unreasonable – he is not satisfied with the simple algorithm any more. Since the moment of development he tries to improve it.

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Issue. Where? When? R

11 months, 3 weeks ago
imageWhile behind a window temperature on the way to the next records, it is interesting to look and what in general there were temperatures in any interval, for any years for the last several decades in 30 000 points worldwide. And can not lose with days of issue and take them those days when there is some "statistical benefit" in the selected location on warm weather, and can be on cold, having estimated it visually on any of three types of charts. Well or it is possible just to rotate the globe, to visually evaluate a variety of temperatures and "as this world is beautiful".

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Immersion cooling comes to new heights: 250 kW on a rack from BitFury

1 year, 1 month ago


The BitFury company brings cooling with immersion to a new round of development: the manual declared intention to construct a new farm for a mining of cryptocurrency which power will make about 40 MW. At the same time about 250 kW will fall on one rack. For achievement of the specified purposes of BitFury is going to use the equipment from 3M.

The new object will be the world's largest where immersion cooling is used. A main objective — increase in density of placement of the equipment. The farm will be optimized for work with technology of submersible cooling, there will be no many elements of infrastructure characteristic of traditional data-centers. The very high density of placement of the equipment and high performance of work of this equipment — are critical for kriptomayningovy farms.

Trying to find new methods of increase of overall performance of the equipment, the BitFury company purchased Allied Control specializing in two-phase immersion cooling (2PIC) with use of coolant from 3M.

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Lori Timesheets — accounting of time on the CUBA platform

1 year ago


"Time is the capital of the worker of brainwork."
Honoré de Balzac


Often it happens that people give preference to old and usual things, ignoring new, even to itself to the detriment. Here and we long time with persistence used system of accounting of time which did not meet our requirements and constantly created problems literally all — from programmers to accounts department.

General tortures with system of accounting of time, because of lack of time (cm drawing), did not become a strong reason for development of the system. The idea to write the real application for demonstration of opportunities of our CUBA platform rescued a situation. Combining business with pleasure, the system of accounting of time became the first candidate.

At the moment development is complete, the application is implemented in our company, and we are ready to share it with everyone.

In this article I will tell how we in a short time (< 1 мес), ограниченными силами (человек и еще полчеловека) разработали это приложение.

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