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  • Advanced queries in HBase

    - by Teflon Ted
    Given the following HBase schema scenario (from the official FAQ)... How would you design an Hbase table for many-to-many association between two entities, for example Student and Course? I would define two tables: Student: student id student data (name, address, ...) courses (use course ids as column qualifiers here) Course: course id course data (name, syllabus, ...) students (use student ids as column qualifiers here) This schema gives you fast access to the queries, show all classes for a student (student table, courses family), or all students for a class (courses table, students family). How would you satisfy the request: "Give me all the students that share at least two courses in common"? Can you build a "query" in HBase that will return that set, or do you have to retrieve all the pertinent data and crunch it yourself in code?

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  • How to build up a lookup table in microcontroller?

    - by GiGi
    Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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  • is it posible to upload directly to remote server using SFTP on ASP.net MVC

    - by DucDigital
    Hi! I am currently develope something using asp.net MVC, im still quite not experience with it so please help me out. I have a form for user to upload Video. The current ideal concept to upload to remote server is to Upload it to to the current server, then use FTP to push it to a remote server. For me, this is not quite fast since you have to upload to current server (Time x1) and then the current server push to new server (Time x2) so it's double the time. So my idea is to make user upload it to the current server, and WHILE user is uploading, the current server add the file to DB and also send the file to the remote server at the same time using SFTP... is it posible and are there any security hole in this concept? Thank you very much

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  • two android threads and not synchronized data

    - by Sponge
    i have a (perhaps stupid) question: im using 2 threads, one is writing floats and one is reading this floats permanently. my question is, what could happen worse when i dont synchronize them? it would be no problem if some of the values would not be correct because they switch just a little every write operation. im running the application this way at the moment and dont have any problems so i want to know what could happen worse? a read/write conflict would cause a number like 12345 which is written to 54321 and red at the same time appear for example as 54345 ? or could happen something worse? (i dont want to use synchronization to keep the code as fast as possible)

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  • Scalable (half-million files) version control system

    - by hashable
    We use SVN for our source-code revision control and are experimenting using it for non-source-code files. We are working with a large set (300-500k) of short (1-4kB) text files that will be updated on a regular basis and need to version control it. We tried using SVN in flat-file mode and it is struggling to handle the first commit (500k files checked in) taking about 36 hours. On a daily basis, we need the system to be able to handle 10k modified files per commit transaction in a short time (<5 min). My questions: Is SVN the right solution for my purpose. The initial speed seems too slow for practical use. If Yes, is there a particular svn server implementation that is fast? (We are currently using the gnu/linux default svn server and command line client.) If No, what are the best f/oss/commercial alternatives Thanks

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  • C++ union assignment, is there a good way to do this?

    - by Sqeaky
    I am working on a project with a library and I must work with unions. Specifically I am working with SDL and the SDL_Event union. I need to make copies of the SDL_Events, and I could find no good information on overloading assignment operators with unions. Provided that I can overload the assignment operator, should I manually sift through the union members and copy the pertinent members or can I simply come some members (this seems dangerous to me), or maybe just use memcpy() (this seems simple and fast, but slightly dangerous)? If I can't overload operators what would my best options be from there? I guess I could make new copies and pass around a bunch of pointers, but in this situation I would prefer not to do that. Any ideas welcome!

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  • What kind of good approaches use c++ programmers for storing error messages?

    - by Narek
    Say I have a huge code and have different kinds of error messages. For that I want to have a separate place where I store error codes and error messages. For example, for an error that occured because the program could not open a file I stroe: F001 "Can not open a file." "The same error message in another language" "The same error message in third language" What is the best way of storing different kind of error messages and codes in a file for c++ programmer in order to use that in a programme fast and easily? FYI I am working with Qt lib.

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  • which layout engine for finding coordinates of html elements on the web page?

    - by Mexx
    I am doing some web data classification task and was thinking if I could get the co-ordinates of html elements as they would appear on a web-browser without taking into consideration any css or javascript being referred in the web page. My language of programming is c++ and the need results for a couple million of pages, so it has to be fast. I know there is a Microsoft COM component which renders the page in a web browser control and then can be queried for position of different html tags. But this is not suitable in my case as it first renders the whole page which takes up a lot of time. So as I found out, there are open-source layout engines WebKit, Gecko that can probably be used for this. But that's a huge piece of code and I need someone to direct me to the right classes or right modules to look into or any previous/similar work someone has done previously. Also, please let me know what you guys think is a good choice if I want to customize the existing code for use with multiple threads to make it faster. Thanks

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  • What the difference between zend framework and Wordpress as framework ?

    - by justjoe
    i only know wordpress and start to seek another alternative framework, zend. i heard hearsay that zend's better from others framework. if you're "a serous coder", or try to act like one, you need to use it on building your web app. some said zend is better. But it's subjective. It's fast ans secure. But nobody tell me the reason or at leas compare it with with wordpress. ultimate question : Do zend have theme or plugin just like wordpress ? any hint will be helpful

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  • MPMoviePlayerController seems to make 2 calls for each movie

    - by user76328
    I seem to have an issue where an iphone app using the MPMoviePlayerController seems to make 2 calls to the server for each video it wants to play back. This occurs with iphone 3.x OS and libraries but not with iphone 2.x. I know that iphone does progressive download and will make multiple 206 requests, etc. but as far as our back end is concerned the player appears to make 2 separate sessions. This only appears to be an issue with iPhone native apps and not iphone videos played through safari. Additional info from apple: iPhone OS 3.0 added support for streaming audio and video over HTTP, and MPMoviePlayerController must validate the media before playback to determine if it is streaming content or progressively downloaded content. This is the delay you are experiencing. On a fast network, the delay should be minimized. Is this double check causing 2 sessions be created for each video request? Any one else seeing same issue? Is there a remedy?

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  • django url tag performance

    - by zxygentoo
    I was trying to integrate django-voting into my project following the RedditStyleVoting instruction. In my urls.py, i did something like this: url(r'^sections/(?P<object_id>\d+)/(?P<direction>up|down|clear)vote/?$', vote_on_object, dict( model=Section, template_object_name='section', template_name='script/section_confirm_vote.html', allow_xmlhttprequest=True ), name="section_vote", then, in my template: {% vote_by_user user on section as vote %} {% score_for_object section as score %} {% vote_by_user user on section as vote %} {% score_for_object section as score %} {{ score.score|default:0 }} It takes over 1.3s to load the page, but by hard coding it like this: {% vote_by_user user on section as vote %} {% score_for_object section as score %} {{ score.score|default:0 }} I got 50ms. Just avoid the url tag resolving stuff I got a 20+ times performance improvement. Is there something I did wrong? If not, then what's the best practice here, should we do things the right way or the fast way?

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  • Multi-threaded downloader in C# question

    - by blez
    Currently I have multi-threaded downloader class that uses HttpWebRequest/Response. All works fine, it's super fast, BUT.. the problem is that the data needs to be streamed while it's downloading to another app. That means that it must be streamed in the right order, the first chunk first, and then the next in the queue. Currently my downloader class is sync and Download() returns byte[]. In my async multi-threaded class I make for example, list with 4 empty elements (for slots) and I pass each index of the slot to each thread using the Download() function. That simulates synchronization, but that's not what I need. How should I do the queue thing, to make sure the data is streamed as soon as the first chunk start downloading.

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  • Is it possible to generate plain-old XML using Haml?

    - by lsdr
    I've been working on a piece of software where I need to generate a custom XML file to send back to a client application. The current solutions on Ruby/Rails world for generating XML files are slow, at best. Using builder or event Nokogiri, while have a nice syntax and are maintainable solutions, they consume too much time and processing. I definetly could go to ERB, which provides a good speed at the expense of building the whole XML by hand. HAML is a great tool, have a nice and straight-forward syntax and is fairly fast. But I'm struggling to build pure XML files using it. Which makes me wonder, is it possible at all? Does any one have some pointers to some code or docs showing how to do this, build a full, valid XML from HAML?

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  • How do I choose a database?

    - by liamzebedee
    I need a comparison table of some sort for database varieties (MySQL, SQLite etc.). I can't find one. My use case is, I am implementing storage of objects in a distributed hash table. I need a database solution that is: Fast for sorting Simplistic (no users, preferably no additional structures like multiple tables etc.) Concurrent (if possible) Multi-platform File based (not stored in memory primarily) Centralized I will be programming in Go. As I understand, I believe I need what is called a Document Orientated Database, because I am storing objects, identified by keys. EDIT: While I am implementing a DHT, I will also be storing metadata about the objects, such as access counts etc. It would also be preferable to have TLL (time to live)

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  • building an ASP NET MVC site, should i go with linq to sql?

    - by aspm
    so i'm about to start a new website from scratch and i've spent about a week trying to figure out what technology to go with. i'm sold on ASP NET MVC. i'm 100% sure i'm going to love using that. but what i am not so sure about yet is using LINQ 2 SQL. so far i've gathered some data... 1) stack overflow uses it - can't be that bad 2) can be REALLY slow if you don't take advantage of compiled queries 3) will always be slower than ADO net, but can be almost just as fast if using #2 in the proper places 4) is NOT the preferred MS solution (there was a thread here on SO about dropping support) i'm itching to use it, but just want to make sure it's the best for me. i come from a heavy ADO/stored procedure and traditional asp net background (this will be my first experience with ASP MVC).

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  • NoSQL for concurrent reads/writes

    - by Mickael Marrache
    After getting some performance issues for an application using a MySQL database, I'm thinking of using NoSQL solutions. My architecture is as follows: One application receives messages from the network at a high throughput (i.e. 50000 messages/sec). Each message is stored in the DB, so it's important for the write rate to be as fast as the arrival rate. Then, I also have some PHP pages that accesses the DB to get the data stored by the other application. It's important for me that the retrieved data is as relevant as possible (i.e. not old data, let's say not more than 5 seconds old). Also, the data is not critical, so I don't need any security mechanism to avoid losing the data. I see there are a lot of NoSQL solutions, but I don't know if they are all relevant. Could you please provide me some directions. Thanks

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  • What are some good ways to do intermachine locking?

    - by mike
    Our server cluster consists of 20 machines, each with 10 pids of 5 threads. We'd like some way to prevent any two threads, in any pid, on any machine, from modifying the same object at the same time. Our code's written in Python and runs on Linux, if that helps narrow things down. Also, it's a pretty rare case that two such threads want to do this, so we'd prefer something that optimizes the "only one thread needs this object" case to be really fast, even if it means that the "one thread has locked this object and another one needs it" case isn't great. What are some of the best practices?

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  • Dynamically generating high performance functions in clojure

    - by mikera
    I'm trying to use Clojure to dynamically generate functions that can be applied to large volumes of data - i.e. a requirement is that the functions be compiled to bytecode in order to execute fast, but their specification is not known until run time. e.g. suppose I specify functions with a simple DSL like: (def my-spec [:add [:multiply 2 :param0] 3]) I would like to create a function compile-spec such that: (compile-spec my-spec) Would return a compiled function of one parameter x that returns 2x+3. What is the best way to do this in Clojure?

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  • Help with concept - filters and number of items

    - by dreamer
    Please check http://www.alibaba.com/catalogs/cid/702/Laptops.html they have nice filter here with number of items for each. Note one detail - they have locations here. Same thing on olx.com - location and number of items for each category. Now imagine I have tables: [products] (Id, Name, CategoryId, LocationId) [Categories] (Id,Name) [Location] (Id, Name) My question how can I do the same, cause count things even with caching looks expensive? And they give results pretty fast... Please advice with possible ways to do that in ASP.NET, C#, MVC, MS SQL, but avoice simple answers like "count and change" Thank you in advance.

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  • Which language + framework should I use for building standalone clients for my PHP webapp?

    - by Jagira
    Hello, I have a PHP web application which basically maintains a set of user profiles and their records. My users are using the app via browser. I am planning to build a standalone desktop client/app for WINDOWS OS, in which a user can login, retrieve and modify the records. Which language + framework will be simple, fast and lightweight to use? I can think of the following options: Microsoft Visual Basic - simplest? Microsoft Visual C++ Python PHP + bambalam compiler Are there any other options? And which of these is better?

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  • Windows Workflow runs very slowlyh on my DEV machine

    - by Joon
    I am developing an app using WF hosted in IIS as WCF services as a business layer. This runs quickly on any machine running Windows Server 2008 R2, but very slowly on our dev machines, running Windows XP SP3. Yesterday, the workflows were as fast on my dev machine as they are on the server for the whole day. Today, they are back to running slowly again (I rebooted overnight) Has anyone else experienced this problem with workflows running slowly on IIS in XP? What did you do to fix it?

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  • Is it hard problem?

    - by Lukasz Lew
    I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm that will find a point with integer coordinates in the same piece as (x,y) that is closest to the cross point of the two given lines. Note: This is not a homework, this is old Euler-type task that I have absolutely no idea how to approach.

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  • Quick way to do data lookup in PHP

    - by Ghostrider
    I have a data table with 600,000 records that is around 25 megabytes large. It is indexed by a 4 byte key. Is there a way to find a row in such dataset quickly with PHP without resorting to MySQL? The website in question is mostly static with minor PHP code and no database dependencies and therefore fast. I would like to add this data without having to use MySQL if possible. In C++ I would memory map the file and do a binary search in it. Is there a way to do something similar in PHP?

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  • Given a few strings, how many strings can be lexicographically least by modifying the alphabet?

    - by Jackson W
    Number of strings can be huge as in 30000. Given N strings, output which ones can be lexicographically least after modifying the english alphabet. e.g. acdbe...... for example if the strings were: omm moo mom ommnom "mom" is already lexicographically least with the original english alphabet. we can make the word "omm" least by switching "m" and "o" in the alphabet ("abcdefghijklonmpqrstuvwxyz"). the other ones you cant make lexicographically last, no matter what you do. any fast way to do this? I have no ways to approach this except try every single possible alphabet

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  • Best indexing strategy for several varchar columns in Postgres

    - by Corey
    I have a table with 10 columns that need to be searchable (the table itself has about 20 columns). So the user will enter query criteria for at least one of the columns but possibly all ten. All non-empty criteria is then put into an AND condition Suppose the user provided non-empty criteria for column1 and column4 and column8 the query would be: select * from the_table where column1 like '%column1_query%' and column4 like '%column4_query%' and column8 like '%column8_query%' So my question is: am I better off creating 1 index with 10 columns? 10 indexes with 1 column each? Or do I need to find out what sets of columns are queried together frequently and create indexes for them (an index on cols 1,4 and 8 in the case above). If my understanding is correct a single index of 10 columns would only work effectively if all 10 columns are in the condition. Open to any suggestions here, additionally the rowcount of the table is only expected to be around 20-30K rows but I want to make sure any and all searches on the table are fast. Thanks!

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