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  • SQL left join with multiple rows into one row

    - by beardedd
    Basically, I have two tables, Table A contains the actual items that I care to get out, and Table B is used for language translations. So, for example, Table A contains the actual content. Anytime text is used within the table, instead of storing actual varchar values, ids are stored that relate back to text stored in Table B. This allows me to by adding a languageID column to Table B, have multiple translations for the same row in the database. Example: Table A Title (int) Description (int) Other Data.... Table B TextID (int) - This is the column whose value is stored in other tables LanguageID (int) Text (varchar) My question is more a call for suggestions on how to best handle this. Ideally I want a query that I can use to select from the table, and get the text as opposed to the ids of the text out of the table. Currently when I have two text items in the table this is what I do: SELECT C.ID, C.Title, D.Text AS Description FROM (SELECT A.ID, A.Description, B.Text AS Title FROM TableA A, TranslationsTable B WHERE A.Title = B.TextID AND B.LanguaugeID = 1) C LEFT JOIN TranslationsTable D ON C.Description = D.TextID AND D.LanguaugeID = 1 This query gives me the row from Table A I am looking for (using where statements in the inner select statement) with the actual text based on the language ID used instead of the text ids. This works fine when I am only using one or two text items that need to be translated, but adding a third item or more, it starts to get really messy - essentially another left join on top of the example. Any suggestions on a better query, or at least a good way to handle 3 or more text items in a single row?

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  • How to differentiate between exceptions i can show the user, and ones i can't?

    - by Ian Boyd
    i have some business logic that traps some logically invalid situations, e.g. trying to reverse a transaction that was already reversed. In this case the correct action is to inform the user: Transaction already reversed or Cannot reverse a reversing transaction or You do not have permission to reverse transactions or This transaction is on a session that has already been closed or This transaction is too old to be reversed The question is, how do i communicate these exceptional cases back to the calling code, so they can show the user? Do i create a separate exception for each case: catch (ETransactionAlreadyReversedException) MessageBox.Show('Transaction already reversed') catch (EReversingAReversingTransactionException) MessageBox.Show('Cannot reverse a reversing transaction') catch (ENoPermissionToReverseTranasctionException) MessageBox.Show('You do not have permission to reverse transactions') catch (ECannotReverseTransactionOnAlredyClosedSessionException) MessageBox.Show('This transaction is on a session that has already been closed') catch (ECannotReverseTooOldTransactionException) MessageBox.Show('This transaction is too old to be reversed') Downside for this is that when there's a new logical case to show the user: Tranasctions created by NSL cannot be reversed i don't simply show the user a message, and instead it leaks out as an unhandled excpetion, when really it should be handled with another MessageBox. The alternative is to create a single exception class: `EReverseTransactionException` With the understanding that any exception of this type is a logical check, that should be handled with a message box: catch (EReverseTransactionException) But it's still understood that any other exceptions, ones that involve, for example, an memory ECC parity error, continue unhandled. In other words, i don't convert all errors that can be thrown by the ReverseTransaction() method into EReverseTransactionException, only ones that are logically invalid cause of the user.

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  • plot 4 different plots inside 1 pdf

    - by ifreak
    I have 2 data frames which i want to generate 3 plots from them and place them inside 1 pdf file as a single column. i want all the plots to have the same x-axis limits(basically the same x-axis) even thought they differ in the name and how they were obtained. the dataframes looks something like that: d1 X Y Z 0.04939317 -0.4622222 13651 0.03202451 -0.4261000 13401 0.09950793 -0.3233025 13151 0.11548556 -0.4637981 12486 0.09817597 -0.4751886 12236 0.15770701 -0.5819355 11986 and d2 V0 V1 V2 V3 sign 1 1 0.379 0.612 pos 2 1 0.378 0.620 pos 3 1 0.578 0.571 neg 4 1 0.978 0.561 pos 5 1 0.758 0.261 neg 6 1 0.378 0.126 neg P.S : both data frames are bigger than this, this is only a part of them V0, V1 and Z range from 1 to 20000 the plots that i created are : From d2 d2plot=ggplot(d1, aes(V0,V1, fill=sign)) + geom_tile()+ scale_fill_manual(values = c("neg" = "yellow", "pos"="red")) +geom_vline(xintercept =10000 ) +geom_text(mapping=aes(x=10000,y=0, label="Stop"), size=4, angle=90, vjust=-0.4, hjust=0) From d1 d1plot = ggplot(d2) + geom_errorbarh(aes(x=z,xmin=z-50,xmax=z+50, y=Y, height = 0.02),color="red")+ opts(legend.position = "none") +geom_vline(xintercept = 10000) +geom_text(mapping=aes(x=10000,y=-0.3, label="Stop"), size=4, angle=90, vjust=-0.4, hjust=0) i've tried grid.arrange(d1plot,d2plot,ncol=1) but the x-axis is different for each plot, i tried changing the aspect ratio, but this will change the y-axis ..i've also tried to use facet_wrap but the problem that my x-axis values have different values, i just want the limits and breaks to be the same and the plots all be aligned in 1 column based on 1 x-axis to comapre the value of the statistical methods in an easy way.

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  • LINQ to SQL - Insert yielding strange behavior.

    - by Isaac
    Hi, I'm trying to insert several newly created items to the database. I have a LINQ2SQL generated class called "Order". Inside order, there's a property called "OrderItems" which is also generated by LINQ2SQL and represents the Items of that Order. So far so good. The problem I'm having right now, is when I try to add more than one newly created OrderItem inside Order. I.E: Order o = orderWorker.GetById( 10 ); for( int i=0; i < 5; ++i ) { OrderItem oi =new OrderItem { Order = order, Price = 100, ShippingPrice = 100, ShippingMethod = ... }; o.OrderItems.Add( oi ); } context.SubmitChanges(); Unfortunately, only a single entity is being added. Yes, I checked the generated SQL by adding Context.Log = Console.Out, and yes, only one statement was created. Any clues? By the way I know I'm not using InsertOnSubmit, by the documentation says: You can explicitly request Inserts by using InsertOnSubmit. Alternatively, LINQ to SQL can infer Inserts by finding objects connected to one of the known objects that must be updated. For example, if you add an Untracked object to an EntitySet(TEntity) or set an EntityRef(TEntity) to an Untracked object, you make the Untracked object reachable by way of tracked objects in the graph. While processing SubmitChanges, LINQ to SQL traverses the tracked objects and discovers any reachable persistent objects that are not tracked. Such objects are candidates for insertion into the database. Thank you very much for your time.

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  • Methods to see result fo a code change faster

    - by Can't Tell
    This question came to me when developing using Eclipse. I use JBoss Application Server and use hot code replacement. But this option requires that the 'build automatically' option to be enabled. This makes Eclipse build the workspace automatically (periodically or when a file is saved?) and for a large code base this takes too much time and processing which makes the machine freeze for a while. Also sometimes an error message is shown saying that hot code replacement failed. The question that I have is: is there a better way to see the result of a code change? Currently I have the following two suggestions: Have unit tests - this will allow to run a single test and see the result of a code change. ( But for a JavaEE application that uses EJBs is it easy to setup unit tests?) Use OSGi - which allows to add jars to the running system without bringing down the JVM. Any ideas on above suggestions or any other suggestion or a framework that allows to do this is welcome.

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  • Speed comparison - Template specialization vs. Virtual Function vs. If-Statement

    - by Person
    Just to get it out of the way... Premature optimization is the root of all evil Make use of OOP etc. I understand. Just looking for some advice regarding the speed of certain operations that I can store in my grey matter for future reference. Say you have an Animation class. An animation can be looped (plays over and over) or not looped (plays once), it may have unique frame times or not, etc. Let's say there are 3 of these "either or" attributes. Note that any method of the Animation class will at most check for one of these (i.e. this isn't a case of a giant branch of if-elseif). Here are some options. 1) Give it boolean members for the attributes given above, and use an if statement to check against them when playing the animation to perform the appropriate action. Problem: Conditional checked every single time the animation is played. 2) Make a base animation class, and derive other animations classes such as LoopedAnimation and AnimationUniqueFrames, etc. Problem: Vtable check upon every call to play the animation given that you have something like a vector<Animation>. Also, making a separate class for all of the possible combinations seems code bloaty. 3) Use template specialization, and specialize those functions that depend on those attributes. Like template<bool looped, bool uniqueFrameTimes> class Animation. Problem: The problem with this is that you couldn't just have a vector<Animation> for something's animations. Could also be bloaty. I'm wondering what kind of speed each of these options offer? I'm particularly interested in the 1st and 2nd option because the 3rd doesn't allow one to iterate through a general container of Animations. In short, what is faster - a vtable fetch or a conditional?

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  • Visual Studio 2008 linker wants all symbols to be resolved, not only used ones

    - by user343011
    We recently upgraded to Visual Studio 2008 from 2005, and I think those error started after that. In our solution, we have a multitude of projects. Many of those are utility projects, or projects containing core functionality used by other projects. The output of those is lib files that are linked to when building the projects generating the final binaries using the "Project dependencies..." option. One of the other projects---Let us call it ResultLib---generates a DLL, and it needs one single function from the core project. This function uses only static function from its own source file, but the project in its entirety uses a lot of low-level Windows functions and also imports a DLL---Let us call it Driver.dll. Our problem is that when building ExtLib, the linker complains about a multitude of unresolved externals, for example all functions exported from Driver.dll, since its lib file is not specified when linking. If we try to fix this by adding all lib files used by other projects that use all of the core project, our resulting ResultLib DLL ends up importing Driver.dll and also exporting all functions defined in it. How do we tell Visual Studio to only try to resolve symbols that are actually used?

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  • Setting Session/Cookie via ajax request made on other website

    - by user596805
    Hi, That's my problem: I have an website, example.com, in which index.html file a introduced a <script src="website.net/js.js"></script> You can see, that this is on other web server. In the js.js I have some data that I want to send to php. For that, I am using Ajax. So, I made a request to "website.net/data.php" using method get. In data.php file everything is ok,I received the value, but I want to set a cookie which value is what I received through ajax. Here is the problem. The setcookie function says that the cookie was set, but when I check in the browser, there's no cookie! It works fine if the index.html file where I use <script src="website.net/js.js"></script> is hosted on the same domain where I am making the request. If it is on another domain, it doesn't work anymore. I have read something about Ajax cross site, but I don't want to send something back to example.com. All I want is to send some data from example.com to website.net and then setting a cookie based on that value. Thank you very much, and sorry for my English! Later edit: I am not used with this website. From the example.net I take a single value. On website.net I receive that value, I check if it's not already a cookie set, if it's not, I set it. On the same page, website.net, I use this cookie too.

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  • What's the correct place to share application logic in CakePHP?

    - by Pichan
    I guess simple answer to the question would be a component. Although I agree, I feel weird having to write a component for something so specific. For example, let's say I have a table of users. When a user is created, it should form a chain reaction of events, initiating different kinds of data related to the user all around the database. I figured it would be best to avoid directly manipulating the database from different controllers and instead pack all that neatly in a method. However since some logic needs to be accesed separately, I really can't have the whole package in a single method. Instead I thought it would be logical to break it up to smaller pieces(like $userModelOrController->createNew() and $candyStorageModelOrController->createNew()) that only interact with their respective database table. Now, if the logic is put to the model, it works great until I need to use other models. Of course it's possible, but when compared to loading models in a controller, it's not that simple. It's like a Cake developer telling me "Sure, it's possible if you want to do it that way but that's not how I would do it". Then, if the logic is put to the controller, I can access other models really easy through $this->loadModel(), but that brings me back to the previously explained situation since I need to be able to continue the chain reaction indefinitely. Accessing other controllers from a controller is possible, but again there doesn't seem to be any direct way of doing so, so I'm guessing I'm still not doing it right. By using a component this problem could be solved easily, since components are available to every controller I want. But like I wrote at the beginning, it feels awkward to create a component specifically for this one task. To me, components seem more like packages of extra functionality(like the core components) and not something to share controller-specific logic. Since I'm new to this whole MVC thing, I could've completely misunderstood the concept. Once again, I would be thankful if someone pointed me to the right direction :)

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  • Where can I view rountrip information in my ASP.NET application?

    - by ajax81
    Hi All, I'm playing around with storing application settings in my database, but I think I may have created a situation where superfluous roundtrips are being made. Is there an easy way to view roundtrips made to an MS Access (I know, I know) backend? I guess while I'm here, I should ask for advice on the best way to handle this project. I'm building an app that generates links based on file names (files are numbered ints, 0-5000). The files are stored on network shares, arranged by name, and the paths change frequently as files are bulk transfered to create space, etc. Example: Files 1000 - 2000 go to /path/1000s Files 2001 - 3000 go to /path/2000s Files 3001 - 4000 go to /path/3000s etc I'm sure by now you can see where I'm going with this. Ultimately, I'm trying to avoid making a roundtrip to get the paths for every single file as they are displayed in a gridview. I'm open to the notion that I've gone about this all wrong and that my idea might be rubbish. I've toyed around with the notion of just creating a flat file, but if I do that, do I still run into the problem of having that file opened and closed for every file displayed in a gridview?

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  • Using the standard OBJECT tag, how can I display a java applet with automatic prompts to install Java and with fallback content?

    - by CB
    This is the code i'm currently using: (note - %s is replaced on the server side) <!--[if !IE]>--> <object type="application/x-java-applet" width="300" height="300" > <!--<![endif]--> <!--[if IE]> <object classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" codebase="http://java.sun.com/update/1.6.0/jinstall-6u22-windows-i586.cab" type="application/x-java-applet" width="300" height="300" > <!--><!-- <![endif]--> <param name="codebase" value="/media/vnc/" > <param name="archive" value="TightVncViewer.jar" /> <param name="code" value="com.tightvnc.vncviewer.VncViewer" /> <param name="port" value="%s" /> <param name="Open New Window" value="yes" /> </object> When Java is installed, this works perfectly in both IE and Firefox. When Java is not installed, IE and Firefox both correctly prompt for an autodownload of Java 1.6 from the codebase line. (IE via the activex url given firefox via the Plugin Finder Service) Now, suppose I want fallback content to be shown if the plugin isn't installed, say a simple message like "Get Java". From reading the specs, i'd assume this should not change the plugin finding prompt - that is, rendering the fallback should be seen as a failure to render the object tag. Thus, I should still get the plugin finder service prompting me to install Java. Instead, simply adding a single character to the innerHTML of the object element causes Firefox to no longer prompt. Test this by visiting data:text/html,<object type='application/x-java-applet'>Java failed to load</object>. How can I keep firefox prompting to install Java while providing fallback content? URL to test Firefox's Java Plugin Finder Service: data:text/html,<object type='application/x-java-applet'/>

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  • how can you have the same form handle by javascript multiple times on the same page?

    - by DeChamp
    I have a thumb gallery where I am using ajax/javascript to submit a form per image to report the image as broken seamlessly along with php. The form and script is templated so the script is in the header and then the form is printed multiple times on the same page with a hidden field with a different id for the value per thumb. So basically this is what i have. javascript in header just a quick idea of the forms i have. Just a quick idea not what I actually have. image1 followed by the form image2 followed by the form So when you hit the button it basically submits all of the forms at the same time. I am sure it can be fixed with a (this) or something like that so it only submits a single form at a time. Let me know please. $(function() { $(".submit").click(function() { var imgId = $("#imgId").val(); var dataString = 'imgId='+ imgId; if(imgId==''){ $('.success').fadeOut(200).hide(); $('.error').fadeIn(200).show(); $('.error').fadeOut(200).hide(); }else{ $.ajax({ type: "POST", url: "inc/brokenImgReport.php", data: dataString, success: function(){ }); $('.error').fadeOut(200).hide(); $('.success').fadeIn(200).show(); setTimeout(function() { $('.success').fadeOut(200); }, 2000); } return false; }); });

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  • Optimize INSERT / UPDATE / DELETE operation

    - by clime
    I wonder if the following script can be optimized somehow. It does write a lot to disk because it deletes possibly up-to-date rows and reinserts them. I was thinking about applying something like "insert ... on duplicate key update" and found some possibilities for single-row updates but I don't know how to apply it in the context of INSERT INTO ... SELECT query. CREATE OR REPLACE FUNCTION update_member_search_index() RETURNS VOID AS $$ DECLARE member_content_type_id INTEGER; BEGIN member_content_type_id := (SELECT id FROM django_content_type WHERE app_label='web' AND model='member'); DELETE FROM watson_searchentry WHERE content_type_id = member_content_type_id; INSERT INTO watson_searchentry (engine_slug, content_type_id, object_id, object_id_int, title, description, content, url, meta_encoded) SELECT 'default', member_content_type_id, web_member.id, web_member.id, web_member.name, '', web_user.email||' '||web_member.normalized_name||' '||web_country.name, '', '{}' FROM web_member INNER JOIN web_user ON (web_member.user_id = web_user.id) INNER JOIN web_country ON (web_member.country_id = web_country.id) WHERE web_user.is_active=TRUE; END; $$ LANGUAGE plpgsql; EDIT: Schemas of web_member, watson_searchentry, web_user, web_country: http://pastebin.com/3tRVPPVi. (content_type_id, object_id_int) in watson_searchentry is unique pair in the table but atm the index is not present (there is no use for it). This script should be run at most once a day for full rebuilds of search index.

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  • C++ BigInt multiplication conceptual problem

    - by Kapo
    I'm building a small BigInt library in C++ for use in my programming language. The structure is like the following: short digits[ 1000 ]; int len; I have a function that converts a string into a bigint by splitting it up into single chars and putting them into digits. The numbers in digits are all reversed, so the number 123 would look like the following: digits[0]=3 digits[1]=3 digits[2]=1 I have already managed to code the adding function, which works perfectly. It works somewhat like this: overflow = 0 for i ++ until length of both numbers exceeded: add numberA[ i ] to numberB[ i ] add overflow to the result set overflow to 0 if the result is bigger than 10: substract 10 from the result overflow = 1 put the result into numberReturn[ i ] (Overflow is in this case what happens when I add 1 to 9: Substract 10 from 10, add 1 to overflow, overflow gets added to the next digit) So think of how two numbers are stored, like those: 0 | 1 | 2 --------- A 2 - - B 0 0 1 The above represents the digits of the bigints 2 (A) and 100 (B). - means uninitialized digits, they aren't accessed. So adding the above number works fine: start at 0, add 2 + 0, go to 1, add 0, go to 2, add 1 But: When I want to do multiplication with the above structure, my program ends up doing the following: Start at 0, multiply 2 with 0 (eek), go to 1, ... So it is obvious that, for multiplication, I have to get an order like this: 0 | 1 | 2 --------- A - - 2 B 0 0 1 Then, everything would be clear: Start at 0, multiply 0 with 0, go to 1, multiply 0 with 0, go to 2, multiply 1 with 2 How can I manage to get digits into the correct form for multiplication? I don't want to do any array moving/flipping - I need performance!

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  • jQuery select by two name roots and perform one of two function depending on which root was selected

    - by RetroCoder
    I'm trying to get this code to work in jQuery and I'm trying to make sure that for each iteration of each root element, its alternate root element for that same iteration doesn't contain anything. Otherwise it sets the .val("") property to an empty string. Looking for a simple solution if possible using search, find, or swap. Each matching number is on the same row level and the same iteration count. I have two input types of input text elements with two different root names like so: 1st Root is "rootA" <input type="text" name="rootA1" /> <input type="text" name="rootA2 /> <input type="text" name="rootA3" /> 2nd Root is "rootB" <input type="text" name="rootB1" /> <input type="text" name="rootB2 /> <input type="text" name="rootB3" /> On blur if any of rootA is called call function fnRootA();. On blur if any of rootB is called call function fnRootB();. Again, I'm trying to make sure that for each iteration like 1 that the alternate root doesn't contain anything, else it sets the .val("") property to an empty string of the root being blurred. My current code works for a single element but wanted to use find or search but not sure how to construct it.. $("input[name='rootA1']").blur(function(e) { fnRootA(1); // this code just removes rootA1's value val("") //if rootB1 has something in it value property // the (1) in parenthesis is the iteration number });

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  • Passing System classes as constructor parameters

    - by mcl
    This is probably crazy. I want to take the idea of Dependency Injection to extremes. I have isolated all System.IO-related behavior into a single class so that I can mock that class in my other classes and thereby relieve my larger suite of unit tests of the burden of worrying about the actual file system. But the File IO class I end up with can only be tested with integration tests, which-- of course-- introduces complexity I don't really want to deal with when all I really want to do is make sure my FileIO class calls the correct System.IO stuff. I don't need to integration test System.IO. My FileIO class is doing more than simply wrapping System.IO functions, every now and then it does contain some logic (maybe this is the problem?). So what I'd like is to be able to test my File IO class to ensure that it makes the correct system calls by mocking the System.IO classes themselves. Ideally this would be as easy as having a constructor like so: public FileIO( System.IO.Directory directory, System.IO.File file, System.IO.FileStream fileStream ) { this.Directory = directory; this.File = file; this.FileStream = fileStream; } And then calling in methods like: public GetFilesInFolder(string folderPath) { return this.Directory.GetFiles(folderPath) } But this doesn't fly since the System.IO classes in question are static classes. As far as I can tell they can neither be instantiated in this way or subclassed for the purposes of mocking.

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  • Avoiding duplication in setting properties on the task in Rake tasks

    - by Stray
    I have a bunch of rake building tasks. They each have unique input / output properties, but the majority of the properties I set on the tasks are the same each time. Currently I'm doing that via simple repetition like this: task :buildThisModule => "bin/modules/thisModule.swf" mxmlc "bin/modules/thisModule.swf" do |t| t.input = "src/project/modules/ThisModule.as" t.prop1 = value1 t.prop2 = value2 ... (And many more property=value sets that are the same in each task) end task :buildThatModule => "bin/modules/thatModule.swf" mxmlc "bin/modules/thatModule.swf" do |t| t.input = "src/project/modules/ThatModule.as" t.prop1 = value1 t.prop2 = value2 ... (And many more property=value sets that are the same in each task) end In my usual programming headspace I'd expect to be able to break out the population of the recurring task properties to a re-usable function. Is there a rake analogy for this? Some way I can have a single function where the shared properties are set on any task? Something equivalent to: task :buildThisModule => "bin/modules/thisModule.swf" mxmlc "bin/modules/thisModule.swf" do |t| addCommonTaskParameters(t) t.input = "src/project/modules/ThisModule.as" end task :buildThatModule => "bin/modules/thatModule.swf" mxmlc "bin/modules/thatModule.swf" do |t| addCommonTaskParameters(t) t.input = "src/project/modules/ThatModule.as" end Thanks.

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  • Wrong label for a nodereference in Drupal content-type

    - by MPD
    We have a content-type built using CCK. One of the fields is a node reference. The node picker is using a view to build the options. A few days ago, everything was working well. Today, it looks like all node reference fields using views to populate the selection options are displaying the wrong label. Every single label in the option is ``A'', but the actual node number is correct. The form actually works, just the labels are incorrect. We have tried just about every combination of edit/save, disable/enable, reboot, clear cache, clone the view, rebuild the view, new view, etc, but we still have a big list of As. If we create a brand new content type with a brand new node reference field, we get the problem. Through some backup/restore exercises, we have determined that the problem is actually in the database and not in the code. We can restore our last good backup, but we will lose a decent amount of work we have put into other parts of the database. We enabled mysql query logging, and the view is actually being called properly, but we cannot track down where the problem is creeping in after that (unraveling the CCK / Views / Drupal plumbing is a challenge). The install was build with latest stable versions as of April. The problems referred to in http://drupal.org/node/624422 is similar, but our code versions include the patches mentioned. Any ideas would be appreciated. Thanks.

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  • Progressbar behaves strangely

    - by wanderameise
    I just created an application in C# that uses a thread which polls the UART for a receive event. If data is received an event is triggered in my main thread (GUI) and a progress bar is controlled via PerformStep() method (of course, I previously set the Max value accordingly). PerformStep is invoked using the following expression to handle cross threading this.Invoke((Action)delegate{progressBar2.PerformStep();}) When running this application the progressbar never hits its final value. It stops at 80%. When debugging and stopping at the line mentioned above, everything works fine using single steps. I have no idea what is going one! Start read thread on main thread: pThreadWrite = new Thread(new ThreadStart(ReadThread)); pThreadWrite.Start(); Read Thread: private void ReadThread() { while(1) { if (ReceiveEvent) { FlashProgressBar(); } } } Event that is triggered in main thread: private void FlashProgressBar() { this.Invoke((Action)delegate { progressBar2.PerformStep();}); } (It's a simplified representation of my code) It seems as if the internal progress is faster than the visual one.

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  • Does Interlocked guarantee visibility to other threads in C# or do I still have to use volatile?

    - by Lirik
    I've been reading the answer to a similar question, but I'm still a little confused... Abel had a great answer, but this is the part that I'm unsure about: ...declaring a variable volatile makes it volatile for every single access. It is impossible to force this behavior any other way, hence volatile cannot be replaced with Interlocked. This is needed in scenarios where other libraries, interfaces or hardware can access your variable and update it anytime, or need the most recent version. Does Interlocked guarantee visibility of the atomic operation to all threads, or do I still have to use the volatile keyword on the value in order to guarantee visibility of the change? Here is my example: public class CountDownLatch { private volatile int m_remain; // <--- do I need the volatile keyword there since I'm using Interlocked? private EventWaitHandle m_event; public CountDownLatch (int count) { Reset(count); } public void Reset(int count) { if (count < 0) throw new ArgumentOutOfRangeException(); m_remain = count; m_event = new ManualResetEvent(false); if (m_remain == 0) { m_event.Set(); } } public void Signal() { // The last thread to signal also sets the event. if (Interlocked.Decrement(ref m_remain) == 0) m_event.Set(); } public void Wait() { m_event.WaitOne(); } }

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  • Calling a network State check from other activities

    - by Laurent
    I realize this question has been answered before but couldn't find an answer that deals with my specific case. I want to create a class called "InternetConnectionChecks" that will handle checking a network state and http timeouts. I'll call the methods twice in the app (once at the beginning to get data from a server, and once at the end to send user orders to the server). For good form I'd like to put all these methods in a single class rather than copy/paste at different points in my code. To check the network state, I'm using ConnectivityManager; thing is, getSystemService requires a class that extends Activity. package arbuckle.app; import android.app.Activity; import android.app.Service; import android.content.Context; import android.net.ConnectivityManager; import android.net.NetworkInfo; public class InternetConnectionChecks extends Activity { public boolean isNetworkAvailable(){ ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo(); if ((activeNetworkInfo != null)&&(activeNetworkInfo.isConnected())){ return true; }else{ return false; } } } QUESTION: if I call the method isNetworkAvailable from another activity, am I: - going to hit up serious errors. - violating good coding form? *If this isn't the right way to do things, can you point me in the right direction to set up a separate class I can call on to check internet connection? Thanks everyone!

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  • How lucene indexing ?

    - by user312140
    Hello I read some document about lucene ; also i read the document in this link ( http://lucene.sourceforge.net/talks/pisa ) . I don't really understand how lucene index documents and don't understand lucene work with which algorithm for indexing ? On above link , said lucene use this algorithm for indexing : * incremental algorithm: o maintain a stack of segment indices o create index for each incoming document o push new indexes onto the stack o let b=10 be the merge factor; M=8 for (size = 1; size < M; size *= b) { if (there are b indexes with size docs on top of the stack) { pop them off the stack; merge them into a single index; push the merged index onto the stack; } else { break; } } How this algorithm help us to have an optimize indexing ? Does lucene use B-tree algorithm or any other algorithm like that for indexing or have a paticular algorithm ? Thank you for reading my post .

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  • Java: refactoring static constants

    - by akf
    We are in the process of refactoring some code. There is a feature that we have developed in one project that we would like to now use in other projects. We are extracting the foundation of this feature and making it a full-fledged project which can then be imported by its current project and others. This effort has been relatively straight-forward but we have one headache. When the framework in question was originally developed, we chose to keep a variety of constant values defined as static fields in a single class. Over time this list of static members grew. The class is used in very many places in our code. In our current refactoring, we will be elevating some of the members of this class to our new framework, but leaving others in place. Our headache is in extracting the foundation members of this class to be used in our new project, and more specifically, how we should address those extracted members in our existing code. We know that we can have our existing Constants class subclass this new project's Constants class and it would inherit all of the parent's static members. This would allow us to effect the change without touching the code that uses these members to change the class name on the static reference. However, the tight coupling inherent in this choice doesn't feel right. before: public class ConstantsA { public static final String CONSTANT1 = "constant.1"; public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } after: public class ConstantsA extends ConstantsB { public static final String CONSTANT1 = "constant.1"; } public class ConstantsB { public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } In our existing code branch, all of the above would be accessible in this manner: ConstantsA.CONSTANT2 I would like to solicit arguments about whether this is 'acceptable' and/or what the best practices are.

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  • Python script to delete old SVN files lacks permission

    - by Rosarch
    I'm trying to delete old SVN files from directory tree. shutil.rmtree and os.unlink raise WindowsErrors, because the script doesn't have permissions to delete them. How can I get around that? Here is the script: # Delete all files of a certain type from a direcotry import os import shutil dir = "c:\\" verbosity = 0; def printCleanMsg(dir_path): if verbosity: print "Cleaning %s\n" % dir_path def cleandir(dir_path): printCleanMsg(dir_path) toDelete = [] dirwalk = os.walk(dir_path) for root, dirs, files in dirwalk: printCleanMsg(root) toDelete.extend([root + os.sep + dir for dir in dirs if '.svn' == dir]) toDelete.extend([root + os.sep + file for file in files if 'svn' in file]) print "Items to be deleted:" for candidate in toDelete: print candidate print "Delete all %d items? [y|n]" % len(toDelete) choice = raw_input() if choice == 'y': deleted = 0 for filedir in toDelete: if os.path.exists(filedir): # could have been deleted already by rmtree try: if os.path.isdir(filedir): shutil.rmtree(filedir) else: os.unlink(filedir) deleted += 1 except WindowsError: print "WindowsError: Couldn't delete '%s'" % filedir print "\nDeleted %d/%d files." % (deleted, len(toDelete)) exit() if __name__ == "__main__": cleandir(dir) Not a single file is able to be deleted. What am I doing wrong?

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  • Why do I have to specify pure virtual functions in the declaration of a derived class in Visual C++?

    - by neuviemeporte
    Given the base class A and the derived class B: class A { public: virtual void f() = 0; }; class B : public A { public: void g(); }; void B::g() { cout << "Yay!"; } void B::f() { cout << "Argh!"; } I get errors saying that f() is not declared in B while trying do define void B::f(). Do I have to declare f() explicitly in B? I think that if the interface changes I shouldn't have to correct the declarations in every single class deriving from it. Is there no way for B to get all the virtual functions' declarations from A automatically? EDIT: I found an article that says the inheritance of pure virtual functions is dependent on the compiler: http://www.objectmentor.com/resources/articles/abcpvf.pdf I'm using VC++2008, wonder if there's an option for this.

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