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  • Suggest Cassandra data model for an existing schema

    - by Andriy Bohdan
    Hello guys! I hope there's someone who can help me suggest a suitable data model to be implemented using nosql database Apache Cassandra. More of than I need it to work under high loads and large amounts of data. Simplified I have 3 types of objects: Product Tag ProductTag Product: key - string key name - string .... - some other fields Tag: key - string key name - unique tag words ProductTag: product_key - foreign key referring to product tag_key - foreign key referring to tag rating - this is rating of tag for this product Each product may have 0 or many tags. Tag may be assigned to 1 or many products. Means relation between products and tags is many-to-many in terms of relational databases. Value of "rating" is updated "very" often. I need to be run the following queries Select objects by keys Select tags for product ordered by rating Select products by tag order by rating Update rating by product_key and tag_key The most important is to make these queries really fast on large amounts of data, considering that rating is constantly updated.

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  • Indexing only one MySQL column value

    - by BrainCore
    I have a MySQL InnoDB table with a status column. The status can be 'done' or 'processing'. As the table grows, at most .1% of the status values will be 'processing,' whereas the other 99.9% of the values will be 'done.' This seems like a great candidate for an index due to the high selectivity for 'processing' (though not for 'done'). Is it possible to create an index for the status column that only indexes the value 'processing'? I do not want the index to waste an enormous amount of space indexing 'done.'

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  • Can a CouchDB document update handler get an update conflict?

    - by jhs
    How likely is a revision conflict when using an update handler? Should I concern myself with conflict-handling code when writing a robust update function? As described in Document Update Handlers, CouchDB 0.10 and later allows on-demand server-side document modification. Update handlers can process non-JSON formats; but the other major features are these: An HTTP front-end to arbitrarily complex document modification code Similar code needn't be written for all possible clients—a DRY architecture Execution is faster and less likely to hit a revision conflict I am unclear about the third point. Executing locally, the update handler will run much faster and with lower latency. But in situations with high contention, that does not guarantee a successful update. Or does the update handler guarantee a successful update?

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  • Quickest and easiest way to implement speech to text conversion for a small speech subset.

    - by sgtpeppers
    Hi, I want to implement a system that receives speech through a microphone on my Mac OS x. I know arbitrary speech recognition is close to impossible without training the system so I'm willing to restrict it to 10 simple sentences. It must recognize with a high degree of accuracy which of these 10 sentences are being spoken, generate the text and add an entry to a remote MySQL database. With these being the architecture of the system I want to implement, could anyone give me an overview of what would be the best way to go about implementing this system? I'm looking for ideas like open source libraries to minimize the coding as this is just a prototype application for a demonstration. Basically I'm looking for a quick and easy solution. Thanks!

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  • typesafe NotifyPropertyChanged using linq expressions

    - by bitbonk
    Form Build your own MVVM I have the following code that lets us have typesafe NotifyOfPropertyChange calls: public void NotifyOfPropertyChange<TProperty>(Expression<Func<TProperty>> property) { var lambda = (LambdaExpression)property; MemberExpression memberExpression; if (lambda.Body is UnaryExpression) { var unaryExpression = (UnaryExpression)lambda.Body; memberExpression = (MemberExpression)unaryExpression.Operand; } else memberExpression = (MemberExpression)lambda.Body; NotifyOfPropertyChange(memberExpression.Member.Name); } How does this approach compare to standard simple strings approach performancewise? Sometimes I have properties that change at a very high frequency. Am I safe to use this typesafe aproach? After some first tests it does seem to make a small difference. How much CPU an memory load does this approach potentially induce?

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  • Why darcs instead of git?

    - by Ctrl Alt D-1337
    Using pure functional languages can have a lot of benefits over using impure imperatives but low level systems languages will generally allow you to achieve much greater performance especially when they are imperative because it allows you to specify the exact steps in how the cpu should compute the result. If there is ever list of tools where high performance is an absolute must then I would put source version controls systems right at the top of that list and git achieves this very well but performance is not it's only advantage over many other other types of version control systems anyway. The git team are handling the unsafe c code very well and I never worry about my type system or any other features of the language it is written in so why is it that there is a lot of haskell developers that must use darcs when they will only be using the finished product?

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  • Mysql out of disk space

    - by Paddy
    I have just finished developing a rails app which has a mysql db as a backend. The app is meant for high traffic and will store lots of information. I am planning to set up my own web server and host the site from it. If in future my disk space runs out i would want to expand by adding more space. But say if my mysql database is housed in my /disk0s1 and by adding a new drive i have more partitions (and hence more disk space), how then would i extend my database to store information on those partitions too, and at the same time prevent any information from being written on the original partition. Should i go for multiple databases? if so how? If i went for a hosting solution i wouldn't be bothering about this as i would just have to worry about making payments for the extra space :) I always wondered how space is added on-the-go by these webhosts. Is there any specific mysql configuration that i have to make?

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  • From admin to dev [closed]

    - by Terry
    Recently a friend of mine had gone from a high level NOC position to a developer. Before that he was just doing the help desk stuff. He has no degree, only the usual MIS/networking certifications and as far as I know only tinkers with code on the weekends. I can see where in some scenarios having a good understanding of configurations, packets, users, OU's, etc would be extremely beneficial to a developer. My question is this, how many full time developers started off this way? Even how many people dual wield the responsibility of developer/systems administrator/network administration?

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  • Only show activities from a specific gadget in OpenSocial

    - by corné
    I created a gadget which is able to post activities: function postActivity(text) { var params = {}; params[opensocial.Activity.Field.TITLE] = text; var activity = opensocial.newActivity(params); opensocial.requestCreateActivity(activity, opensocial.CreateActivityPriority.HIGH); }; And I request activities by doing: req.add(req.newFetchActivitiesRequest( new opensocial.IdSpec({'userId' : 'VIEWER', 'groupId' : 'FRIENDS'})), 'friends_activities'); My question is: How can I filter activities to only show activities posted by a specific gadget? I reckon the field "appId" is meant for this, but this field is empty in the response.

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  • Are "EXC_BREAKPOINT (SIGTRAP)" exceptions caused by debugging breakpoints?

    - by Dennis
    I have a multithreaded app that is very stable on all my test machines and seems to be stable for almost every one of my users (based on no complaints of crashes). The app crashes frequently for one user, though, who was kind enough to send crash reports. All the crash reports (~10 consecutive reports) look essentially identical: Date/Time: 2010-04-06 11:44:56.106 -0700 OS Version: Mac OS X 10.6.3 (10D573) Report Version: 6 Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000002, 0x0000000000000000 Crashed Thread: 0 Dispatch queue: com.apple.main-thread Thread 0 Crashed: Dispatch queue: com.apple.main-thread 0 com.apple.CoreFoundation 0x90ab98d4 __CFBasicHashRehash + 3348 1 com.apple.CoreFoundation 0x90adf610 CFBasicHashRemoveValue + 1264 2 com.apple.CoreText 0x94e0069c TCFMutableSet::Intersect(__CFSet const*) const + 126 3 com.apple.CoreText 0x94dfe465 TDescriptorSource::CopyMandatoryMatchableRequest(__CFDictionary const*, __CFSet const*) + 115 4 com.apple.CoreText 0x94dfdda6 TDescriptorSource::CopyDescriptorsForRequest(__CFDictionary const*, __CFSet const*, long (*)(void const*, void const*, void*), void*, unsigned long) const + 40 5 com.apple.CoreText 0x94e00377 TDescriptor::CreateMatchingDescriptors(__CFSet const*, unsigned long) const + 135 6 com.apple.AppKit 0x961f5952 __NSFontFactoryWithName + 904 7 com.apple.AppKit 0x961f54f0 +[NSFont fontWithName:size:] + 39 (....more text follows) First, I spent a long time investigating [NSFont fontWithName:size:]. I figured that maybe the user's fonts were screwed up somehow, so that [NSFont fontWithName:size:] was requesting something non-existent and failing for that reason. I added a bunch of code using [[NSFontManager sharedFontManager] availableFontNamesWithTraits:NSItalicFontMask] to check for font availability in advance. Sadly, these changes didn't fix the problem. I've now noticed that I forgot to remove some debugging breakpoints, including _NSLockError, [NSException raise], and objc_exception_throw. However, the app was definitely built using "Release" as the active build configuration. I assume that using the "Release" configuration prevents setting of any breakpoints--but then again I am not sure exactly how breakpoints work or whether the program needs to be run from within gdb for breakpoints to have any effect. My questions are: could my having left the breakpoints set be the cause of the crashes observed by the user? If so, why would the breakpoints cause a problem only for this one user? If not, has anybody else had similar problems with [NSFont fontWithName:size:]? I will probably just try removing the breakpoints and sending back to the user, but I'm not sure how much currency I have left with that user. And I'd like to understand more generally whether leaving the breakpoints set could possibly cause a problem (when the app is built using "Release" configuration).

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  • How to resolve this very heavy query that slows down the application?

    - by Juan Paredes
    Hi, We have a web application running in a production enviroment and at some point the client complained about how slow the application got. When we checked what was going on with the application and the database we discover this "precious" query that was being executed by several users at the same time (thus inflicting a extremely high load on the database server): SELECT NULL AS table_cat, o.owner AS table_schem, o.object_name AS table_name, o.object_type AS table_type, NULL AS remarks FROM all_objects o WHERE o.owner LIKE :1 ESCAPE :"SYS_B_0" AND o.object_name LIKE :2 ESCAPE :"SYS_B_1" AND o.object_type IN(:"SYS_B_2", :"SYS_B_3") ORDER BY table_type, table_schem, table_name Our application does not execute this query, I believe it is an Hibernate internal query. I've found little information on why Hibernate does this extremely heavy query, so any help is very much appreciated! The production enviroment information: Red Hat Enterprise Linux 5.3 (Tikanga), JDK 1.5, web container OC4J (whitin Oracle Application Server), Oracle Database 10g Release 10.0.0.1, JDBC Driver for JDK 1.2 and 1.3, Hibernate version 3.2.6.ga. Thank you.

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  • Code Golf: Beehive

    - by LiraNuna
    The challenge The shortest code by character count that will generate a beehive from user input. A beehive is defined a a grid of hexagons in a size inputted by the user as two positive numbers greater than zero (no need to validate input). The first number (W) represents the width of the beehive - or - how many hexagons are on each row. The second number (H) represents the height of the beehive - or - how many hexagons are on each column. A Single hexagon is made from three ASCII characters: _, / and \, and three lines: __ / \ \__/ Hexagons complete each other: the first column of the beehive will be 'low', and the second will be high - alternating and repeating in the same pattern forming W hexagons. This will be repeated H times to form a total of WxH hexagons. Test cases: Input: 1 1 Output: __ / \ \__/ Input: 4 2 Output: __ __ __/ \__/ \ / \__/ \__/ \__/ \__/ \ / \__/ \__/ \__/ \__/ Input: 2 5 Output: __ __/ \ / \__/ \__/ \ / \__/ \__/ \ / \__/ \__/ \ / \__/ \__/ \ / \__/ \__/ Input: 11 3 Output: __ __ __ __ __ __/ \__/ \__/ \__/ \__/ \__ / \__/ \__/ \__/ \__/ \__/ \ \__/ \__/ \__/ \__/ \__/ \__/ / \__/ \__/ \__/ \__/ \__/ \ \__/ \__/ \__/ \__/ \__/ \__/ / \__/ \__/ \__/ \__/ \__/ \ \__/ \__/ \__/ \__/ \__/ \__/ Code count includes input/output (i.e full program).

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  • Developing Mobile App (Iphone,Blackberry,Android) for an existing website

    - by soodos
    Hey Guys I have a website and am planning to develop a mobile version of it for the iphone, blackberry and android. My website is a social network built on PHP Zend framework. Now all these mobile apps are going to be having the same functionality like the website. I am little ignorant about this - but from a high level I understand that all these mobile apps should not have to write any backend logic. For every functionality - they will simply make a web service API call to interact with the backend. So does that mean, for every functionality I need to create a web service method. Can the existing code be re used - I'm a little lost - Can someone shed some light on this matter or point me in the right direction (like some articles) Thanks

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  • What Simple Changes Made the Biggest Improvements to Your Delphi Programs

    - by lkessler
    I have a Delphi 2009 program that handles a lot of data and needs to be as fast as possible and not use too much memory. What small simple changes have you made to your Delphi code that had the biggest impact on the performance of you program by noticeably reducing execution time or memory use? Thanks everyone for all your answers. Many great tips. For completeness, I'll post a few important articles on Delphi optimization that I found. Before you start optimizing Delphi code at About.com Speed and Size: Top 10 Tricks also at About.com Code Optimization Fundamentals and Delphi Optimization Guidelines at High Performance Delphi, relating to Delphi 7 but still very pertinent.

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  • Super wide, but not so tall, bitmap?

    - by Erik Karlsson
    Howdy folks. Is there any way to create a more space/resource efficient bitmap? Currently i try to render a file, approx 800 px high but around 720000px wide. It crashes my application, presumebly because of the share memory-size of the bitmap. Can i do it more efficient, like creating it as an gif directly and not later when i save it? I try to save a series of lines/rectangles from a real world reading, and i want it to be 1px per 1/100th of a second. Any input? And btw, i never manage to ogon using google open id : /

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  • How to put a newline into a column header in an xtable in R

    - by PaulHurleyuk
    I have a dataframe that I am putting into a sweave document using xtable, however one of my column names is quite long, and I would like to break it over two lines to save space calqc_table<-structure(list(RUNID = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), ANALYTEINDEX = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), ID = structure(1:11, .Label = c("Cal A", "Cal B", "Cal C", "Cal D", "Cal E", "Cal F", "Cal G", "Cal H", "Cal High", "Cal Low", "Cal Mid"), class = "factor"), mean_conc = c(200.619459644855, 158.264703128903, 102.469121407733, 50.3551544728544, 9.88296440865076, 4.41727762501703, 2.53494715706024, 1.00602831741361, 199.065054555735, 2.48063347296935, 50.1499780776199), sd_conc = c(2.3275711264554, NA, NA, NA, NA, NA, NA, 0.101636943231162, 0, 0, 0), nrow = c(3, 1, 1, 1, 1, 1, 1, 3, 2, 2, 2)), .Names = c("Identifier of the Run within the Study", "ANALYTEINDEX", "ID", "mean_conc", "sd_conc", "nrow"), row.names = c(NA, -11L ), class = "data.frame") calqc_xtable<-xtable(calqc_table) I have tried putting a newline into the name, but this didn't seem to work names(calqc_table)[1]<-"Identifier of the \nRun within the Study" Is there a way to do this ? I have seen someone suggest using the latex function from the hmisc package to manually iterate over the table and write it out in latex manually, including the newline, but this seems like a bit of a faf !

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  • Subclassing UIScrollView for drawing w/o views

    - by David Dunham
    I'm contemplating subclassing UIScrollView (the way UITextView does) to draw a fairly large amount of text (formatted in ways that NSTextView can't). So far the view won't actually scroll. I'm setting contentSize, and when I drag, I see the scroll indicator. But nothing changes (and I don't get a drawRect: message). An alternate approach is to use a child view, and I've done this. The view can be over 5000 pixels high, however, and I'm a bit concerned about performance on an actual device. (The other approach, be like UITableView, would be a huge pain -- I'm "porting" Mac Cocoa code, and a collection of views would be a huge architecture change.) I've done some searching, but haven't found anyone who is using UIScrollView to do the drawing. Has anyone done this and know of any pitfalls?

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  • AS3: How to access pixel data efficiently?

    - by JonoRR
    I'm working a game. The game requires entities to analyse an image and head towards pixels with specific properties (high red channel, etc.) I've looked into Pixel Bender, but this only seems useful for writing new colors to the image. At the moment, even at a low resolution (200x200) just one entity scanning the image slows to 1-2 Frames/second. I'm embedding the image and instance it as a Bitmap as a child of the stage. The 1-2 FPS situation is using BitmapData.getPixel() (on each pixel) with a distance calculation beforehand. I'm wondering if there's any way I can do this more efficiently... My first thought was some sort of spatial partioning coupled with splitting the image up into many smaller pieces. I also feel like Pixel Bender should be able to help somehow, however I've had little experience with it. Cheers for any help. Jonathan

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  • JD Edwards... call C#?

    - by rbobby
    Hey all, I know very little about JD Edwards. I have a client asking how to call an API we supply (as COM, C#, REST) from JD Edwards. I'm not getting much in terms of high quality answers from their tech guy... so I thought I'd ask here. Can JD Edwards call C#? Can JD Edwards call Java? Can JD Edwards call a Unix scipt? Can anyone point me towards anything useful in terms of developer/customization documentation? Thanks!

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  • Which Cortex-M3 interrupts can I use for general purpose work?

    - by Captain NedD
    I'd have some code that needs to be run as the result of a particular interrupt going off. I don't want to execute it in the context of the interrupt itself but I also don't want it to execute in thread mode. I would like to run it at a priority that's lower than the high level interrupt that precipitated its running but also a priority that higher than thread level (and some other interrupts as well). I think I need to use one of the other interrupt handlers. Which ones are the best to use and what the best way to invoke them? At the moment I'm planning on just using the interrupt handlers for some peripherals that I'm not using and invoking them by setting bits directly through the NVIC but I was hoping there's a better, more official way. Thanks,

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  • Minimum Acceptable Code Coverage Numbers in the real world.

    - by Pita.O
    Hi, I am in the middle of putting together some guidelines around code coverage and I want to specify a number that really makes sense. It's easy to repeat the 100% mantra that I see all over the internet without considering the cost benefit analysis and when diminishing returns actually sets in. I solicit comments from persons who have actually reported code coverage on real-life, medium/large-sized projects. What percentages were you seeing? How much is too much? I really want some balance (in figures) that will help developers produce hight quality code. Is 65% coverage too low to expect? Is 80% too high?

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  • Bit manipulation, permutate bits

    - by triktae
    Hi. I am trying to make a loop that loops through all different integers where exactly 10 of the last 40 bits are set high, the rest set low. The reason is that I have a map with 40 different values, and I want to sum all different ways ten of these values can be multiplied. (This is just out of curiosity, so it's really the "bitmanip"-loop that is of interest, not the sum as such.) If I were to do this with e.g. 2 out of 4 bits, it would be easy to set all manually, 0011 = 7, 0101 = 5, 1001 = 9, 0110 = 6, 1010 = 10, 1100 = 12, but with 10 out of 40 I can't seem to find a method to generate these effectively. I tried, starting with 1023 ( = 1111111111 in binary), finding a good way to manipulate this, but with no success. I've been trying to do this in C++, but it's really the general method(if any) that is of interest. I did some googling, but with little success, if anyone has a good link, that would of course be appreciated too. :)

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  • PHP application variable... maybe?

    - by James
    I went to a PHP job interview, I was asked to implement a piece of code to detect visitors are bots to crawl thru the website and steal content. So I implemented a few lines of code to detect if the site is being refreshed/visited too quickly/often by using a session variable to store last visit timestamp. I got told that session varaibles can be manupilated by cookies etc, so I am wondering if there is a application variable that I can use to store the timestamp information against visitor IPs eg $_SERVER[REMOTE_ADDR]? I know that I can write the data to a file but it's not very good for a high traffic website. Regards James

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  • EF and design pattern

    - by kathy
    Hello, I’m working on a high volume transactional enterprise application(asp.net, windows app, oracle app as client) which has been designed using n-tire application and SOA architecture .The application was developed in the .NET platform utilizing C#,VB.NET, Framework 3.5 (I’m planning to upgrade to the , Framework 4.0), EF( EF in the data layer level) and WCF(WCF services in the service layer level) Since this is the first project using EF, and having read about using EF in n-tier and SOA applications, and the features available in the EF Feature, I have the following points: Which design pattern should I use in EF( Simple Entities, Change Set, Self-Tracking Entities and DTOs) in the data layer level In addition Which design pattern should I use in the other tier and layer to get the best practices of EF Thanks

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  • LNK1106 with big binary resource

    - by E Dominique
    I have a rather huge .dat-file (896MB) included as a BIN resource in my project. Now I get a LNK1106 link error ("fatal error LNK1106: invalid file or disk full: cannot seek to 0x382A3920".) I use Visual Studio 2005 under Windows XP, and have tried on a 4GB RAM machine with high Virtual Memory settings and lots of disk space. I have tried a number of different optimization flags, but to no avail. Does anyone have a clue? EDIT: I have narrowed it down to a specific size of the compiled resource. If the .res file is 544078588 bytes (about 518.9MB) or larger, the error occurs. If it is smaller it works just fine. Still no solution, though...

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