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• What is the performance penalty of XML data type in SQL Server when compared to NVARCHAR(MAX)?

  - by Piotr Owsiak

  I have a DB that is going to keep log entries. One of the columns in the log table contains serialized (to XML) objects and a guy on my team proposed to go with XML data type rather than NVARCHAR(MAX). This table will have logs kept "forever" (archiving some very old entries may be considered in the future). I'm a little worried about the CPU overhead, but I'm even more worried that DB can grow faster (FoxyBOA from the referenced question got 70% bigger DB when using XML). I have read this question http://stackoverflow.com/questions/514827/microsoft-sql-server-2005-2008-xml-vs-text-varchar-data-type and it gave me some ideas but I am particulairly interrested in clarification on whether the DB size increases or decreases. Can you please share your insight/experiences in that matter. BTW. I don't currently have any need to depend on XML features within SQL Server (there's nearly zero advantage to me in the specific case). Ocasionally log entries will be extracted, but I prefer to handle the XML using .NET (either by writing a small client or using a function defined in a .NET assembly).

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• CakePHP: Custom Function in bootstrap that uses $ajax->link not working

  - by nekko

  Hello I have two questions: (1) Is it best practice to create global custom functions in the bootstrap file? Is there a better place to store them? (2) I am unable use the following line of code in my custom function located in my bootstrap.php file: $url = $ajax->link ( 'Delete', array ('controller' => 'events', 'action' => 'delete', 22 ), array ('update' => 'event' ), 'Do you want to delete this event?' ); echo $url; I receive the following error: Notice (8): Undefined variable: ajax [APP\config\bootstrap.php, line 271] Code } function testAjax () { $url = $ajax->link ( 'Delete', array ('controller' => 'events', 'action' => 'delete', 22 ), array ('update' => 'event' ), 'Do you want to delete this event?' ); testAjax - APP\config\bootstrap.php, line 271 include - APP\views\event\queue.ctp, line 19 View::_render() - CORE\cake\libs\view\view.php, line 649 View::render() - CORE\cake\libs\view\view.php, line 372 Controller::render() - CORE\cake\libs\controller\controller.php, line 766 Dispatcher::_invoke() - CORE\cake\dispatcher.php, line 211 Dispatcher::dispatch() - CORE\cake\dispatcher.php, line 181 [main] - APP\webroot\index.php, line 91 However it works as intended if I place that same code in my view: <a onclick=" event.returnValue = false; return false;" id="link1656170149" href="/shout/events/delete/22">Delete</a> Please help :) Thanks in advance!!

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• Delphi Performance: Case Versus If

  - by Andreas Rejbrand

  I guess there might be some overlapping with previous SO questions, but I could not find a Delphi-specific question on this topic. Suppose that you want to check if an unsigned 32-bit integer variable "MyAction" is equal to any of the constants ACTION1, ACTION2, ... ACTIONn, where n is - say 1000. I guess that, besides being more elegant, case MyAction of ACTION1: {code}; ACTION2: {code}; ... ACTIONn: {code}; end; if much faster than if MyAction = ACTION1 then // code else if MyAction = ACTION2 then // code ... else if MyAction = ACTIONn then // code; I guess that the if variant takes time O(n) to complete (i.e. to find the right action) if the right action ACTIONi has a high value of i, whereas the case variant takes a lot less time (O(1)?). Am I correct that switch is much faster? Am I correct that the time required to find the right action in the switch case actually is independent of n? I.e. is it true that it does not really take any longer to check a million cases than to check 10 cases? How, exactly, does this work?

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• How do you make a static sprite be a child of another sprite in cocos2D while using SpaceManager

  - by JJBigThoughts

  I have two static (STATIC_MASS) SpaceManager sprites. One is a child of the other - by which I mean that one sort of builds up the other one, but although the child's images shows up in the right place, the child doesn't seem to exists in the chipmunk physics engine, like I would expect. In my case, I have a backboard (rectangular sprite) and a hoop (a circular sprite). Since I might want to move the backboard, I'd like to attach the hoop to backboard so that the hoop automatically moves right along with the backboard. Here, we see a rotating backboard with attached hoop. It looks OK on the screen, but other objects only bounce off the backboard but pass right through the hoop (in a bad sense of the term). What doesn't my child sprite seem to exist in the physics engine? // Add Backboard cpShape *shapeRect = [smgr addRectAt:cpvWinCenter mass:STATIC_MASS width:200 height:10 rotation:0.0f ];// We're upgrading this cpCCSprite * cccrsRect = [cpCCSprite spriteWithShape:shapeRect file:@"rect_200x10.png"]; [self addChild:cccrsRect]; // Spin the static backboard: http://stackoverflow.com/questions/2691589/how-do-you-make-a-sprite-rotate-in-cocos2d-while-using-spacemanager // Make static object update moves in chipmunk // Since Backboard is static, and since we're going to move it, it needs to know about spacemanager so its position gets updated inside chipmunk. // Setting this would make the smgr recalculate all static shapes positions every step // cccrsRect.integrationDt = smgr.constantDt; // cccrsRect.spaceManager = smgr; // Alternative method: smgr.rehashStaticEveryStep = YES; smgr.rehashStaticEveryStep = YES; // Spin the backboard [cccrsRect runAction:[CCRepeatForever actionWithAction: [CCSequence actions: [CCRotateTo actionWithDuration:2 angle:180], [CCRotateTo actionWithDuration:2 angle:360], nil] ]]; // Add the hoop cpShape *shapeHoop = [smgr addCircleAt:ccp(100,-45) mass:STATIC_MASS radius: 50 ]; cpCCSprite * cccrsHoop = [cpCCSprite spriteWithShape:shapeHoop file:@"hoop_100x100.png"]; [cccrsRect addChild:cccrsHoop]; This is only half working for me. Note: SpaceManager is a toolkit for working with cocos2D-iphone

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• Approach for fixing NoClassDefFoundError?

  - by DJC

  I'm seeing this question is getting asked a lot in many different contexts. Perhaps we can set some strategies for locating and fixing it? I'm noobish myself so all I can contribute are horror stories and questions, sorry... It seems this is thrown when a class is visible at compile time but not at run time... how can this happen? In my case I am developing an app that uses the Google APIs, in Eclipse, for the Android platform. I've configured the Project Properties / Java Build Path / Libraries to include the gdata .jars and all is well. When I execute in the emulator I get a force close and the logcat shows a NoClassDefFoundError on a simple new ContactsService("myApp"); I've also tried a new CalendarService("myApp") with the same results. Is it possible or desirable to statically bind at compile time to avoid the problem? How could dynamic binding of an add-on library work in the mobile environment anyway? Either it has to be bound into my .apk or else I need to "install" it? ... hmmm. Advice much appreciated.

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• AS3 variables handling by AVM/compiler/scope

  - by jchmielewski

  I have couple of questions about AS3 variables handling by AVM/compiler/scope .1. This code in Flash will throw an error: function myFunction() { var mc:MovieClip=new MovieClip(); var mc:MovieClip=new MovieClip(); } but it won`t throw an error in Flex (only warning in Editor). Why? .2. How Flash sees variables in loops? Apparently this: for (var i:int=0; i<2; i++) { var mc:MovieClip=new MovieClip(); } isn`t equal to just: var mc:MovieClip=new MovieClip(); var mc:MovieClip=new MovieClip(); because it will throw an error again as earlier in Flash, but in Flex in function not? Is Flash changing somehow my loop before compilation? .3. Where in a class in equivalent to timeline in Flash - where in class I would put code which I put normally on timeline (I assume it is not constructor because of what I have written earlier, or maybe it`s a matter of Flash/Flex compiler)?

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• How do I ensure my C# software can access the internet in a Citrix + ISA environment?

  - by TomFromThePool

  Hi everyone, A client recently informed us that deployment of our software in their environment has failed due to a proxy error when the software attempts to access the internet. The client has a combination of Citrix and Microsoft's ISA server. The software allows the use of a proxy and the ability to manually enter authentication information, or automatically retrieve the current system proxy settings. The error returned is the standard 407 authentication error, but the client assures us that they have entered the authentication information required. They have also shown us the snippet of the ISA error logs which identify the client as Anonymous and the authentication protocol as Basic. I have a few questions I suppose: How should I go about dealing with the ISA server in my code? I have no real experience with this environment and am assuming that the ISA server is treated like any other proxy. If I am mistaken, what should I be doing? Does ISA allow the administrator to disallow specific authentication protocols - and if this is the case and 'Basic' auth is disallowed, would it still return a 407 error? Could the Citrix environment have caused this issue? Is there any particular way to ensure that my software will work in such an environment? Code-samples would be much appreciated. I have neither a Citrix test server or an ISA server at my disposal to carry out testing on this so I am currently trying to identify possible causes before I make the case for investment in a more robust testing environment. Thanks for any help!

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• ipad tabbar rotation

  - by MaKo

  hi, please help with this noob questions but really making me go crazy if I create a project from scratch (using windows based app) for the ipad, and add a tabbar , with firstviewController, and secondviewController, it works fine, starts in landscape mode, but in info.plist I set it to Landscape(left home button), but really in simulator starts with the button on the right side! in the FirstViewController.m (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { if (interfaceOrientation == UIInterfaceOrientationLandscapeLeft || interfaceOrientation == UIInterfaceOrientationLandscapeRight) return YES; else { return NO; }} so it starts in landscape, and rotates as the simulator rotates, but if I create a template app for iphone tabbar, set the info.plist Initial interface orientation Landscape (left home button) and add the code above, IT DOESNT WORK!!! simulator starts with button at left but tab bar on the side, same problem that I had with an app that Im porting from iphone to ipad, (landscape intended) I get to the landscape start mode, but the tab bar remains on the side! also the only way to make the old ported app to show the simulator on the side was with UIInterfaceOrientation UIIntefaceOrientationLandscapeLeft (didnt work with Initial interface orientation), does not let me choose the value for the key, but it shows the simulator on landscape,, so,, what can I do please to show the tab bar on landscape mode??? the tabbar from scratch was made to see if the code will work , but it didnt?? why does it work in the tab bar made from windows app and not tab bar app? I just want the tab bar to show in landscape ahhh, thanks

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• Time delay an external RSS feed

  - by x3ja

  I subscribe to a number of RSS feeds, mostly from within my own timezone (UK: currently GMT+1, a.k.a BST). However I'm also interested in news from New Zealand (currently GMT+12). My problem is caused by my addiction to needing to keep my unread count at, or near, zero. When I load up my RSS reader in the mornings it has gathered all the NZ news at once (normally around 100 items) and I feel compelled either to read them all or to mark them all as read to feed my need for zero-unread-count. I figured a good solution to this would be to time delay the RSS feed somehow, so I would be drip-fed the stories at their time +12 hours, so I could read them through the day as they come in. So my question (or, rather, questions): Does such a thing exist currently & what is it? (no point reworking the wheel) If not: What would be the best way to approach doing this myself? I have access to a Linux web server on which I can run scripts, create databases, store files etc, so there should be a way... I'm most conversant in perl and have done a little fiddling with XML within that, so would naturally process ... or is there some simpler way to do it that I'm missing?

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• Practical rules for premature optimization

  - by DougW

  It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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• How can I get back my privilege to create a new database in MySQL?

  - by Steven

  I can not use MySQL. MySQL is on my local computer. Currently I added skip-grant-tables in My.ini so I can use MySQL. But I have no privilege to create a new database. My problem is tough, although I asked related questions on SO, but no answer can resolve my problem. I almost give up. So I lower my expectation. I am developing a website, so I need to create database, tables and operate tables. You don't have to consider security. Is there a simple solution that can give me privilege to create a new database? Maybe by adding some command in my.ini or something? You won't need to completely resolve my problem. Maybe after the development, I will upload the database and tables to another server(The current database server is my personal computer, windows XP) so I can uninstall and reinstall MySQL. The root of problem is that I lack privileges.

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• How to use generic (NSObject) controller with subviews of a UIViewController?

  - by wanderlust

  I have a UIViewController that is loading several subviews at different times based on user interaction. I originally built all of these subviews in code, with no nib files. Now I am moving to nib files with custom UIView subclasses. Some of these subviews display static data, and I am using loadNibNamed:owner:options: to load them into the view controller. Others contain controls that I need to access. I (sort of) understand the reasons Apple says to use one view controller per screen of content, using generic controller objects (NSObjects) to manage subsections of a screen. So I need a view controller, a generic controller, a view class and a nib. How do I put this all together? My working assumptions and subsequent questions: I will associate the view class with the nib in the 'class identity' drop down in IB. The view controller will coordinate overall screen interactions. When necessary, it will create an instance of the generic controller. Does the generic controller load the nib? How? Do I define the outlets and actions in that view class, or should they be in the generic controller? How do I pass messages between the view controller and the generic controller? If anyone can point me to some sample code using a controller in this way, it will go a long way to helping me understand. None of the books or stackoverflow posts I've read have quite hit the spot yet.

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• Advanced Linq query using into

  - by dilbert789

  I have this query that someone else wrote, it's over my head so I'm looking for some direction. What is happening currently is that it's taking numbers where there is a goal and no history entered, or history and no goal, this screws up the calculations as both goal and history for the same item are required on each. The three tables involved are: KPIType Goal KPIHistory What I need: Need all rows from KPIType. Need all goals where there is a matching KPIHistory row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 1 Need all kpiHistory’s where there is a matching Goal row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 2 Current query: var query = from t in dcs.KPIType.Where(k => k.ID <= 23) join g in dcs.Goal.Where(g => g.Dealership.ID == dealershipID && g.YearMonth >= beginDate && g.YearMonth <= endDate ) on t.ID equals g.KPITypeID into results1 join h in dcs.KPIHistory.Where(h => h.Dealership.ID == dealershipID && h.ForDate >= beginDate && h.ForDate <= endDate ) on t.ID equals h.KPIType.ID into results2 orderby t.DisplayOrder select new { t, Goal = results1, KPIHistory = results2 }; query.ToList().ForEach(q => { results.Add(q.t); }); Thanks, I'm happy to answer questions if more info needed.

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• CSS Design question, I've got myself completely turned around.

  - by Matt Dawdy

  Okay, I have a couple of other questions out there, but I think I'd better just ask from the beginning how you CSS experts would do this. Client's page is split into 2 rows -- header has some info, some aligned to left of page, some to right, some in the middle. This is currently done using a table. I'm fine with leaving this alone or changing it. My real question is that I need a page layout to handle the following: 2 columns - column on left is 200px, but can be "close" down to to 10px (not a slider, it's either 200 or 10 px). The column on the right needs to be as big as it needs to be -- which might be larger than the width of the page. When left column is "closed" then the right column slides over of course. Again, this right column might be 300px or it might be 4000 pixels (it's a reporting interface). Now, to add another wrinkle, SOME pages have 3 columns. The first 2 columns are each exactly 200px, and both can be "closed" down to 10 px each. But, the user may not close both columns, maybe just 1. Or none. Or both. The third column needs to act just like I described above, being able to be larger than the page width, and sliding over to take advantage of any of the "closed" left columns. Whew! I'm pretty confused as to how to go about this, as either I get it right but I can't scroll over to the right at all (overflow: hidden) and information is lost, or the right column jumps down below the left 2 columns and just looks plain stupid. My minimum browser requirements are IE8, FF3.5, Chrome and Safari (latest versions of all). Any and all pointers are gladly accepted.

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• FluentNHibernate, getting 1 column from another table

  - by puffpio

  We're using FluentNHibernate and we have run into a problem where our object model requires data from two tables like so: public class MyModel { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual int FooId { get; set; } public virtual string FooName { get; set; } } Where there is a MyModel table that has Id, Name, and FooId as a foreign key into the Foo table. The Foo tables contains Id and FooName. This problem is very similar to another post here: http://stackoverflow.com/questions/1896645/nhibernate-join-tables-and-get-single-column-from-other-table but I am trying to figure out how to do it with FluentNHibernate. I can make the Id, Name, and FooId very easily..but mapping FooName I am having trouble with. This is my class map: public class MyModelClassMap : ClassMap<MyModel> { public MyModelClassMap() { this.Id(a => a.Id).Column("AccountId").GeneratedBy.Identity(); this.Map(a => a.Name); this.Map(a => a.FooId); // my attempt to map FooName but it doesn't work this.Join("Foo", join => join.KeyColumn("FooId").Map(a => a.FooName)); } } with that mapping I get this error: The element 'class' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'join' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'joined-subclass, loader, sql-insert, sql-update, sql-delete, filter, resultset, query, sql-query' in namespace 'urn:nhibernate-mapping-2.2'. any ideas?

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• Grails or Play! for an ex-RoR developer ?

  - by Kedare

  Hello, I plan to begin learning a Java web framework (I love the Java API), I already used Rails and Django. I want something close to Java, but without all the complexity of J2EE. I've found 2 framework that could be good for me : Grails : Grails looks great, it use Groovy that is better than Java for web application (I think..), but it's slower, that use pure-java components (Hibernate, Strut, Spring), it looks pretty simple to deploy (send .war and it's ok !), the GSP is great ! It's a bit harder to debug (need to restart the server at each modification, and the stacktrace is a mix of Java and Groovy stack that is not always understandable..) Play! : This framework also looks great, it's faster than Grails (It's use directly Java), but I don't really like how it use Java, it modify the source code to transform the properties call as setXXX/getXXX, I'm not kind of that... The framework also have caching function that Grails don't (alreary) has. I don't really like the Template Engine. It's also easer to debug (no need to restart the server, and the stacktrace is clear) What do you recommend for ? I am looking for something easy to learn (I used a lot ruby and java, but a little bit java (But I love the Java API)), that is full featured (That's no a problem with all the Java Library availables, but if it's bundle and integrated I prefer), that scale and that is not too slow (faster than ruby), and if possible I would want something with a decent community to easily find support and answer to my questions ;) PS: No JRuby on Rails Thank you !

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• Calculate the digital root of a number

  - by Gregory Higley

  A digital root, according to Wikipedia, is "the number obtained by adding all the digits, then adding the digits of that number, and then continuing until a single-digit number is reached." For instance, the digital root of 99 is 9, because 9 + 9 = 18 and 1 + 8 = 9. My Haskell solution -- and I'm no expert -- is as follows. digitalRoot n | n < 10 = n | otherwise = digitalRoot . sum . map (\c -> read [c]) . show $ n As a language junky, I'm interested in seeing solutions in as many languages as possible, both to learn about those languages and possibly to learn new ways of using languages I already know. (And I know at least a bit of quite a few.) I'm particularly interested in the tightest, most elegant solutions in Haskell and REBOL, my two principal "hobby" languages, but any ol' language will do. (I pay the bills with unrelated projects in Objective C and C#.) Here's my (verbose) REBOL solution: digital-root: func [n [integer!] /local added expanded] [ either n < 10 [ n ][ expanded: copy [] foreach c to-string n [ append expanded to-integer to-string c ] added: 0 foreach e expanded [ added: added + e ] digital-root added ] ] EDIT: As some have pointed out either directly or indirectly, there's a quick one-line expression that can calculate this. You can find it in several of the answers below and in the linked Wikipedia page. (I've awarded Varun the answer, as the first to point it out.) Wish I'd known about that before, but we can still bend our brains with this question by avoiding solutions that involve that expression, if you're so inclined. If not, Crackoverflow has no shortage of questions to answer. :)

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• How to register application for existing file types using WiX installer?

  - by Marek

  related to this: http://stackoverflow.com/questions/138550/how-to-register-file-types-extensions-with-a-wix-installer but not a duplicate. I need to handle existing file types (.jpg files). I do not want to be the default handler for .jpg, I would just like to extend the "Open with" menu with a link to my app. I see HKCR\.jpg\OpenWithList\ and HKCR\.jpg\OpenWithProgIds\ in the registry but I am not sure whether to write to these and how to do it correctly with WiX. Should I use something like this? <ProgId Id='??what here?' Description='Jpeg handled by my App'> <Extension Id='jpg' ContentType='image/jpeg'> <Verb Id='openwithmyapp' Sequence='10' Command='OpenWithMyApp' Target='[!FileId]' Argument='"%1"' /> </Extension> </ProgId> There are many ways how to fail here (like Photo Mechanics did, the HKCR for image file types is a real mess after I have installed this software) How to do this correctly with WiX?

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• Return enum instead of bool from function for clarity ?

  - by Moe Sisko

  This is similar to : http://stackoverflow.com/questions/2908876/net-bool-vs-enum-as-a-method-parameter but concerns returning a bool from a function in some situations. e.g. Function which returns bool : public bool Poll() { bool isFinished = false; // do something, then determine if finished or not. return isFinished; } Used like this : while (!Poll()) { // do stuff during wait. } Its not obvious from the calling context what the bool returned from Poll() means. It might be clearer in some ways if the "Poll" function was renamed "IsFinished()", but the method does a bit of work, and (IMO) would not really reflect what the function actually does. Names like "IsFinished" also seem more appropriate for properties. Another option might be to rename it to something like : "PollAndReturnIsFinished" but this doesn't feel right either. So an option might be to return an enum. e.g : public enum Status { Running, Finished } public Status Poll() { Status status = Status.Running; // do something, then determine if finished or not. return status; } Called like this : while (Poll() == Status.Running) { // do stuff during wait. } But this feels like overkill. Any ideas ?

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• Close TCP connection when owner process is already killed

  - by Otiel

  I have a Windows service that - when it starts - opens some WCF services to listen on the 8000 port. It happens that this service crashes sometimes. When it does, the TCP connection is not released, thus causing my service to throw an exception if I try to start it again: AddressAlreadyInUseException: There is already a listener on IP endpoint 0.0.0.0:8000 Some observations: When running CurrPorts or netstat -ano, I can see that the 8000 port is still in use (in LISTENING state) and is owned by the Process ID XXX that corresponded to my service process ID. But my service has already crashed, and does not appear in the Task Manager anymore. Thus I can't kill the process to free the port! Of course, running taskkill /PID XXX returns: ERROR: The process "XXX" not found. When running CurrPorts or netstat -b, I can see that the process name involved in creating the listening port is System, and not as MyService.exe (whereas it is MyService.exe when my service is running). I tried to use CurrPorts to close the connection, but I always get the following error message: Failed to close one or more TCP connections. Be aware that you must run this tool as admin in order to close TCP connections. (Useless to say, I do run CurrPorts as Administrator...) TCPView is not much help either: the process name associated to the 8000 port is <non-existent>, and doing "End process" or "Close connection" has no effect. I tried to see if there was not a child process associated with the PID XXX using Process Explorer, but no luck here. If I close my service properly (before it crashes), the TCP connection is correctly released. This is normal, as I close the WCF service hosts in the OnStop() event of my service. The only way I found to release the connection is to restart the server (which is not convenient in a production environment as you can guess). Waiting does not help, the TCP connection is never released. How can I close the connection without restarting the Windows server? PS: found some questions extremely similar to mine.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• What are the worst examples of moral failure in the history of software engineering?

  - by Amanda S

  Many computer science curricula include a class or at least a lecture on disasters caused by software bugs, such as the Therac-25 incidents or Ariane 5 Flight 501. Indeed, Wikipedia has a list of software bugs with serious consequences, and a question on StackOverflow addresses some of them too. We study the failures of the past so that we don't repeat them, and I believe that rather than ignoring them or excusing them, it's important to look at these failures squarely and remind ourselves exactly how the mistakes made by people in our profession cost real money and real lives. By studying failures caused by uncaught bugs and bad process, we learn certain lessons about rigorous testing and accountability, and we make sure that our innocent mistakes are caught before they cause major problems. There are kinds of less innocent failure in software engineering, however, and I think it's just as important to study the serious consequences caused by programmers motivated by malice, greed, or just plain amorality. Thus we can learn about the ethical questions that arise in our profession, and how to respond when we are faced with them ourselves. Unfortunately, it's much harder to find lists of these failures--the only one I can come up with is that apocryphal "DOS ain't done 'til Lotus won't run" story. What are the worst examples of moral failure in the history of software engineering?

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• How to rename goals in Maven?

  - by mjs

  In the Maven document Introduction to the Build Lifecycle, a goal of display:time is described that outputs the current time. The plugin is as follows: ... <plugin> <groupId>com.mycompany.example</groupId> <artifactId>maven-touch-plugin</artifactId> <version>1.0</version> <executions> <execution> <phase>process-test-resources</phase> <goals> <goal>timestamp</goal> </goals> </execution> </executions> </plugin> ... I have several questions relating to this plugin: How can I change the name of the goal to, for example, foo:bar? (Why does neither display nor time appear anywhere in the XML fragment? How can you tell, from looking at the fragment, what goals it defines?) How can I manually run this goal? (For similar constructs, the equivalent of mvn display:time sometimes works, but this doesn't work consistently.) How can I see if this goal exists? (i.e. list available goals; this question suggests this is impossible.)

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• An Ideal Keyboard Layout for Programming

  - by Jon Purdy

  I often hear complaints that programming languages that make heavy use of symbols for brevity, most notably C and C++ (I'm not going to touch APL), are difficult to type because they require frequent use of the shift key. A year or two ago, I got tired of it myself, downloaded Microsoft's Keyboard Layout Creator, made a few changes to my layout, and have not once looked back. The speed difference is astounding; with these few simple changes I am able to type C++ code around 30% faster, depending of course on how hairy it is; best of all, my typing speed in ordinary running text is not compromised. My questions are these: what alternate keyboard layouts have existed for programming, which have gained popularity, are any of them still in modern use, do you personally use any altered layout, and how can my layout be further optimised? I made the following changes to a standard QWERTY layout. (I don't use Dvorak, but there is a programmer Dvorak layout worth mentioning.) Swap numbers with symbols in the top row, because long or repeated literal numbers are typically replaced with named constants; Swap backquote with tilde, because backquotes are rare in many languages but destructors are common in C++; Swap minus with underscore, because underscores are common in identifiers; Swap curly braces with square brackets, because blocks are more common than subscripts; and Swap double quote with single quote, because strings are more common than character literals. I suspect this last is probably going to be the most controversial, as it interferes the most with running text by requiring use of shift to type common contractions. This layout has significantly increased my typing speed in C++, C, Java, and Perl, and somewhat increased it in LISP and Python.

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• Mysql Database Question about Large Columns

  - by murat

  Hi, I have a table that has 100.000 rows, and soon it will be doubled. The size of the database is currently 5 gb and most of them goes to one particular column, which is a text column for PDF files. We expect to have 20-30 GB or maybe 50 gb database after couple of month and this system will be used frequently. I have couple of questions regarding with this setup 1-) We are using innodb on every table, including users table etc. Is it better to use myisam on this table, where we store text version of the PDF files? (from memory usage /performance perspective) 2-) We use Sphinx for searching, however the data must be retrieved for highlighting. Highlighting is done via sphinx API but still we need to retrieve 10 rows in order to send it to Sphinx again. This 10 rows may allocate 50 mb memory, which is quite large. So I am planning to split these PDF files into chunks of 5 pages in the database, so these 100.000 rows will be around 3-4 million rows and couple of month later, instead of having 300.000-350.000 rows, we'll have 10 million rows to store text version of these PDF files. However, we will retrieve less pages, so again instead of retrieving 400 pages to send Sphinx for highlighting, we can retrieve 5 pages and it will have a big impact on the performance. Currently, when we search a term and retrieve PDF files that have more than 100 pages, the execution time is 0.3-0.35 seconds, however if we retrieve PDF files that have less than 5 pages, the execution time reduces to 0.06 seconds, and it also uses less memory. Do you think, this is a good trade-off? We will have million of rows instead of having 100k-200k rows but it will save memory and improve the performance. Is it a good approach to solve this problem and do you have any ideas how to overcome this problem? The text version of the data is used only for indexing and highlighting. So, we are very flexible. Thanks,

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