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When executing queries in ClickHouse to note that in the Profiler on one of the first places frequently visible function LZ_decompress_fast. Why is this happening? This question was the occasion for a study on choosing the best compression algorithm. Here I publish the study as a whole, and the short version you can learn from my report on HighLoad++ Siberia. Data ClickHouse are stored in a compressed form. And during the query execution ClickHouse tries almost nothing to do is to use a minimum of CPU resources. It happens that all the calculations that could be spent time, already well optimized, and the query is user-written. Then it remains to perform the decompression. the Question — why the LZ4 decompression can be a bottleneck? It would seem that LZ4...

Many programmers began to switch from the second version of Python on the third, due to the fact that pretty soon the support for Python 2 will be terminated. The author, a translation of which we have published, says that the bulk of the Python 3 code that he's ever seen, looks like a code with brackets written in Python 2. According to him, he himself suffers from something similar. Here he cites the examples of some of the great features available only to those who use Python 3. He hopes that these opportunities will make life easier for those who know about them. All of the examples in this article, written in Python 3.7. In the description of each feature includes information about the minimum version of Python required for its application. Read more →

Around in every other topic on habré for the space or electronics, the topic comes up of radiation resistance. Through the news about the domestic space permeates the theme of import substitution Redstone circuitry, but at the same time Elon Musk uses cheap common chips and proud of it. And isralite in "Beresite" used radstone processor and also proud of it. Yes, in principle microelectronic industry in Russia lives for the most part at the expense of the state order with the relevant requirements. Monitoring regular disputes about how to build satellites, shows that training of participants is usually low, and their reasoning was burdened by stereotypes, overheard, taken out of context facts and knowledge obsolete many years ago. I thought that reading...

We have in Russia is one attraction that attracts foreigners wildest. But almost every one of us considers it torture. This is the TRANS-Siberian railway: six days by train from Moscow to Vladivostok. The first day you will sleep on the second still somehow survive, but then go crazy. Or use a cheap and practical method of teleportation with the help of vodka. Every time we travel abroad, we are asked, what you need to know about the TRANS-Siberian. And we can't really answer. In General, this is a post-educational program about how not to lose face in front of foreigners, and about what you need to know about this trip. And a reminder for foreigners from English. Well, in an attempt to understand why, that's why they go. And what happy. Our Respondent...

This article continues cycle about backup, Backup, part 1: Why you need to backup, overview of methods, technologies backups, part 2: Review and testing of rsync-based backup tools the Backup part 3: Review and testing duplicity, duplicaty, deja dup backups, part 4: Review and testing zbackup, restic, borgbackup The backup part 5: Testing bacula and veeam backup for linux backups, part 6: Comparison of backup tools backups, part 7: Conclusions As we have already mentioned in the first article, there is a very large number of backup software based on rsync. Of those that are best suited for our conditions, I would consider 3: rdiff-backup, rsnapshot and burp. Read more →

For Many years I used a fairly standardized approach to the design of each new card Cogmind, and although their account already goes on tens, in my blog I never considered. This is mainly due to the fact that detailed analysis of the entire process will require disclosure of a heap of content, because the cards are stacked after the first stages of the game. But after the recent release of Beta 8, which added a very interesting map at the beginning of the game, we have a great opportunity to discuss the design of the cards, not really worrying about spoilers, then that is basically the content and so is quite easy to find. In this article I will go through all the stages of the design process and implementation from beginning to end. In the process of...

Today we will consider just two of the case the data customers and partners are two completely different companies were freely available "due to the" open servers with Elasticsearch logs of information systems (is) these companies. In the first case is tens of thousands (maybe hundreds of thousands) of tickets for different cultural events (theatres, clubs, river walk, etc.) sold through the system", Radio" (www.radario.ru). the second case is information about tours of the thousands (maybe tens of thousands) of travelers, who bought tours through travel agencies connected to the system "to Fly.ru" (www.sletat.ru). note that are not only the names of the companies prevent data from entering the outdoor access, but the approach of these companies to the...

This publication supplements the series of articles "What do you hear on the radio?" the subject of broadcasting on short waves. Mass Amateur movement in our country began with the Assembly of the simplest radios to listen to broadcasts of broadcasting stations. The construction of the detector receiver was published in the journal "Amateur radio", No. 7, 1924 Mass broadcasting in the USSR began in 1922 with "a wave of three thousand meters" (frequency 100 kHz, the range of DV) transmitter output of 12 kW of radio im. Of the Comintern (call RDW). Gradually radio covers the range of SV, and then in the late 20's and early 30's begins to develop broadcasting in HF, including foreign languages (foreign broadcasting). Read more →

TL;DR: IN the. APPX file Universal Windows Platform can be packaged to exe file that will run in Windows 10 (build 1607 and later) about the same as a normal. exe files. It can be used for social engineering attacks, with distribution through e — mail providers do not block APPX files. The file must be signed with a valid digital signature. Universal Windows PlatformUniversal Windows Platform is (relatively) new standard for creating universal apps for Windows 10, Windows 10 Mobile, Xbox One and Hololens. The standard came with the release of Windows 10, and provides an API with a restriction of privileges and isolation, is a container format and metadata inside it. UWP-applications widely presented in the Microsoft Store. They are self-sufficient, safe and...

Not long ago, I worked as a mercenary, jumping from one project to another. With some short-term projects were done for the week. Others lasted a couple of months. They brought enough money to take a vacation. But I prefer short because it was possible to install a large hourly rate. I not only own, but had too much work to make a living. Even my highest rate was quite reasonable and I have always provided high quality service. So it was until, until I was offered a contract in a big company. This company contacted me promptly, and the Manager said that they need a man right now. The employee that will provide maximum productivity with minimal training. Good or bad, but that was my motto. The project I really liked. It was small, fast and paid well. Read...

Recently, we in the team invented and implemented the function of transferring money through the air using Bluetooth LE. I want to tell you how we did it and what Apple provides us with the tools. Many developers think that Bluetooth is difficult, because this is a fairly low-level Protocol, and it is not so many specialists. But it's not as scary and actually use this feature very simple! And those functions which can be implemented using Bluetooth LE is certainly interesting and will allow you to differentiate your application among the competitors. Read more →

Last week there have been three interesting developments in the field of information security was closed exploited a vulnerability in Whatsapp for a critical vulnerability in Windows released patches, even for unsupported versions of the OS and in Intel found another Spectre-like problem. Let's start with vulnerabilities in a component of Remote Desktop Services (news, blog post, Microsoft). The technical details of the vulnerability were not disclosed, but we know that the bug allows to control the system via RDP without logging on. the Vulnerability affects Windows 7 and Windows Server 2008 and unsupported in Windows XP and Windows 2003 Server. In the article Brian Krebs stated on the similarity of the vulnerability EternalBlue bug in the SMB Protocol...

In this article I will talk about their impressions of the conference Google I/O 2019 where my colleagues and I visited the other day (and even “lit up” with our app in one of the presentations). It will help you to feel the atmosphere and may encourage you to look at several reports, posted on the Google Developers channel. the Badoo Developers at Google I/O 2019 Day 0. Preface to get to the conference, you need to win the lottery, which will start in February at Google I/O (typically this is known from the news). But the victory does not get a ticket, but only gives the opportunity to buy it back for $ 1,150. There are other programs that allow you to get a ticket with a big discount or for free, such as Code Jam. Students and staff of universities can...

Most compilers have the following architecture: In this article I'm going to get to dissect the architecture of the item-by-item. it is Possible to say that this article is an addition to the abundant resources available on the topic of compilers. It is an Autonomous source that will allow you to understand the basics of the design and implementation of programming languages. the Target audience of the article — people whose idea of working compilers are extremely limited (maximum is that they are compiling). However, I expect that the reader is versed in structures and algorithms. the Article is in any case not privy to the most modern production compilers with millions of lines of code — no, it's a short course "compilers for dummies", helps you to...

I am a professional participant in the innovation industry. Together with colleagues for the last 10 years we participate in the creation of new technologies. And I have to say about the reason why you should not engage in innovation in Russia. Here it is possible to speculate about the bad investment climate, inefficiency of government programs, the size of the domestic market, offset the motivations of the participants. But there's also a poorly controlled risk, which is the ability to be behind bars. And this is not to say aloud, but necessary. Under the cut is the top 5 innovative companies according to the investigative Committee, known to me, and their misadventures were not previously mentioned on Habre. Read more →