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• Two radically different queries against 4 mil records execute in the same time - one uses brute force.

  - by IanC

  I'm using SQL Server 2008. I have a table with over 3 million records, which is related to another table with a million records. I have spent a few days experimenting with different ways of querying these tables. I have it down to two radically different queries, both of which take 6s to execute on my laptop. The first query uses a brute force method of evaluating possibly likely matches, and removes incorrect matches via aggregate summation calculations. The second gets all possibly likely matches, then removes incorrect matches via an EXCEPT query that uses two dedicated indexes to find the low and high mismatches. Logically, one would expect the brute force to be slow and the indexes one to be fast. Not so. And I have experimented heavily with indexes until I got the best speed. Further, the brute force query doesn't require as many indexes, which means that technically it would yield better overall system performance. Below are the two execution plans. If you can't see them, please let me know and I'll re-post then in landscape orientation / mail them to you. Brute-force query: Index-based exception query: My question is, based on the execution plans, which one look more efficient? I realize that thing may change as my data grows.

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• VB.NET: Dialog exits when enter pressed?

  - by Camilo Martin

  Hi all; My problem seems to be quite simple, but it's not working the intuitive way. I'm designing a Windows Forms Application, and there is a dialog that should NOT exit when the enter key is pressed, instead it has to validate data first, in case enter was pressed after changing the text of a ComboBox. I've tried by telling it what to do on KeyPress event of the ComboBox if e is the Enter key: Private Sub ComboBoxSizeChoose_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles ComboBoxSizeChoose.KeyPress If e.KeyChar = Convert.ToChar(Keys.Enter) Then Try TamanhoDaNovaFonte = Single.Parse(ComboBoxSizeChoose.Text) Catch ex As Exception Dim Dialogo2 As New Dialog2 Dialog2.ShowDialog() ComboBoxSizeChoose.Text = TamanhoDaNovaFonte End Try End If End Sub But no success so far. When the Enter key is pressed, even with the ComboBox on focus, the whole dialog is closed, returning to the previous form. The validation is NOT done at all, and it has to be done before exiting. In fact, I don't even want to exit on the form's enter KeyPress, the only purpose of the enter key on the whole dialog is to validate the ComboBox (but only when in focus, for the sake of an intuitive UI). I've also tried appending the validation to the KeyPress event of the whole dialog's form, if the key is Enter. NO SUCCESS! It's like my code wasn't there at all. What should I do? (Visual Studio 2008, VB.NET)

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• C++ return a "NULL" object if search result not found

  - by aduric

  I'm pretty new to C++ so I tend to design with a lot of Java-isms while I'm learning. Anyway, in Java, if I had class with a 'search' method that would return an object T from a Collection< T that matched a specific parameter, I would return that object and if the object was not found in the collection, I would return a NULL. Then in my calling function I would just check if(T != NULL) { ... } In C++, I'm finding out that I can't return a NULL if the object doesn't exist. I just want to return an 'indicator' of type T that notifies the calling function that no object has been found. I don't want to throw an exception because it's not really an exceptional circumstance. class Node { .... Attr& getAttribute(const string& attribute_name) const { //search collection //if found at i return attributes[i]; //if not found return NULL; } private: vector<Attr> attributes; }

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• Cocos2d and MPMoviePlayerViewController - NSNotificationCenter not working

  - by digi_0315

  I'm using cocos2d with MPMoviePlayerViewController class, but when I tryed to catch notification status when the movie is finished I got this error: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString movieFinishedCallback]: unrecognized selector sent to instance 0x5d23730' my playVideoController.m are: @implementation PlayVideoViewController +(id) scene{ CCScene *scene = [CCScene node]; CCLayer *layer = [credits node]; [scene addChild: layer]; return scene; } -(id)initWithPath:(NSString *)moviePath{ if ((self = [super init])){ movieURL = [NSURL fileURLWithPath:moviePath]; [movieURL retain]; playerViewController = [[MPMoviePlayerViewController alloc] initWithContentURL:movieURL]; player = [playerViewController moviePlayer]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieFinishedCallback) name:MPMoviePlayerPlaybackDidFinishNotification object:player]; [[[CCDirector sharedDirector] openGLView] addSubview:playerViewController.view]; [player play]; } return self; } -(void)movieFinishedCallback{ CCLOG(@"video finished!!"); } in .h: #import <UIKit/UIKit.h> #import "cocos2d.h" #import <MediaPlayer/MediaPlayer.h> @interface PlayVideoViewController : CCLayer { NSURL *movieURL; MPMoviePlayerViewController *playerViewController; MPMoviePlayerController *player; } +(id) scene; @end and I call it in appDelegate.m: - (void) applicationDidFinishLaunching:(UIApplication*)application { CC_DIRECTOR_INIT(); CCDirector *director = [CCDirector sharedDirector]; [director setDeviceOrientation:kCCDeviceOrientationLandscapeLeft]; EAGLView *glView = [director openGLView]; [glView setMultipleTouchEnabled:YES]; [CCTexture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_RGBA8888];//kEAGLColorFormatRGBA8 NSString *path = [[NSBundle mainBundle] pathForResource:@"intro" ofType:@"mov" inDirectory:nil]; vi ewController = [[[PlayVideoViewController alloc] initWithPath:path] autorelease]; } what i'm doing wrong? anyone can help me please?? I'm try to solve it since a lot of hours ago but I can't!

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• OptimisticLockException in inner transaction ruins outer transaction

  - by Pace

  I have the following code (OLE = OptimisticLockException)... public void outer() { try { middle() } catch (OLE) { updateEntities(); outer(); } } @Transactional public void middle() { try { inner() } catch (OLE) { updateEntities(); middle(); } @Transactional public void inner() { //Do DB operation } inner() is called by other non-transactional methods which is why both middle() and inner() are transactional. As you can see, I deal with OLEs by updating the entities and retrying the operation. The problem I'm having is that when I designed things this way I was assuming that the only time one could get an OLE was when a transaction closed. This is apparently not the case as the call to inner() is throwing an OLE even when the stack is outer()->middle()->inner(). Now, middle() is properly handling the OLE and the retry succeeds but when it comes time to close the transaction it has been marked rollbackOnly by Spring. When the middle() method call finally returns the closing aspect throws an exception because it can't commit a transaction marked rollbackOnly. I'm uncertain what to do here. I can't clear the rollbackOnly state. I don't want to force create a transaction on every call to inner because that kills my performance. Am I missing something or can anyone see a way I can structure this differently? EDIT: To clarify what I'm asking, let me explain my main question. Is it possible to catch and handle OLE if you are inside of an @Transactional method? FYI: The transaction manager is a JpaTransactionManager and the JPA provider is Hibernate.

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• Can't use my form

  - by Alexandr

  I have class with my form in folder /application/forms/Auth.php it looks like class Form_Auth extends Zend_Form { public function __construct() { $this->setName(); parent::__construct(); $username = new Zend_Form_Element_Text('username'); $password = new Zend_Form_Element_Password('password'); $mail = new Zend_Form_Element_Text('mail'); $submit = new Zend_Form_Element_Submit('submit'); $this->addElements(array($username,$password,$mail,$submit)); } } When i try create object $this->view->form = new Form_Auth(); is see exeption Application error Exception information: Message: Invalid name provided; must contain only valid variable characters and be non-empty Stack trace: D:\WWW\zends\application\Forms\Auth.php(8): Zend_Form-setName() d:\WWW\zends\application\controllers\RegistrationController.php(49): Form_Auth-__construct() D:\WebServer\ZendFramework\ZendFramework\library\Zend\Controller\Action.php(513): RegistrationController-indexAction() D:\WebServer\ZendFramework\ZendFramework\library\Zend\Controller\Dispatcher\Standard.php(289): Zend_Controller_Action-dispatch('indexAction') D:\WebServer\ZendFramework\ZendFramework\library\Zend\Controller\Front.php(954): Zend_Controller_Dispatcher_Standard-dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http)) D:\WebServer\ZendFramework\ZendFramework\library\Zend\Application\Bootstrap\Bootstrap.php(97): Zend_Controller_Front-dispatch() D:\WebServer\ZendFramework\ZendFramework\library\Zend\Application.php(366): Zend_Application_Bootstrap_Bootstrap-run() D:\WWW\zends\public\index.php(26): Zend_Application-run() {main} Request Parameters: array ( 'controller' = 'registration', 'action' = 'index', 'module' = 'default', ) the version zf is 1.10.3 what i do wrong ?

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• What is wrong with locking non-static fields? What is the correct way to lock a particular instance?

  - by smartcaveman

  Why is it considered bad practice to lock non-static fields? And, if I am not locking non-static fields, then how do I lock an instance method without locking the method on all other instances of the same or derived class? I wrote an example to make my question more clear. public abstract class BaseClass { private readonly object NonStaticLockObject = new object(); private static readonly object StaticLockObject = new object(); protected void DoThreadSafeAction<T>(Action<T> action) where T: BaseClass { var derived = this as T; if(derived == null) { throw new Exception(); } lock(NonStaticLockObject) { action(derived); } } } public class DerivedClass :BaseClass { private readonly Queue<object> _queue; public void Enqueue(object obj) { DoThreadSafeAction<DerivedClass>(x=>x._queue.Enqueue(obj)); } } If I make the lock on the StaticLockObject, then the DoThreadSafeAction method will be locked for all instances of all classes that derive from BaseClass and that is not what I want. I want to make sure that no other threads can call a method on a particular instance of an object while it is locked.

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• DataGridView: Scroll bar does not refreshed

  - by David.Chu.ca

  I am working (fixing bugs) on a project which was written in VS 2005. There is one DataGridView control on a form. When it is first time loaded, the control's data grid is populated with rows of data from a collection manually or in codes. Actually, there is method PopulateDataGrid() do the job. There is also another control on the form. When control is changed, the data grid will be cleared first and then rows are repopulated again through PopulateDataGrid(). The problem is that when the grid is refreshed, the vertical scroll bar does not get reset correctly. I thought it should be. Since the scroll bar is not reset, when I tried to click on grid and move down, I got exception: the max value of scroll bar was exceeded. All the settings for grid control are default values. For example, the ScrollBars is Both. The following is the only related place to set row auto size property: poDataGridView.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.DisplayedCellsExceptHeaders; I am not sure if there is any property I have to set in designer?

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• JDBC call not executing

  - by dbyrne

  I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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• Testing InlineFormset clean methods

  - by Rory

  I have a Django project, with 2 models, a Structure and Bracket, the Bracket has a ForeignKey to a Structure (i.e. one-to-many, one Structure has many Brackets). I created a TabularInline for the admin site, so that there would be a table of Brackets on the Structure. I added a custom formset with some a custom clean method to do some extra validation, you can't have a Bracket that conflicts with another Bracket on the same Structure etc. The admin looks like this: class BracketInline(admin.TabularInline): model = Bracket formset = BracketInlineFormset class StructureAdmin(admin.ModelAdmin): inlines = [ BracketInline ] admin.site.register(Structure, StructureAdmin) That all works, and the validation works. However now I want to write some unittest to test my complex formset validation logic. My first attempt to validate known-good values is: data = {'form-TOTAL_FORMS': '1', 'form-INITIAL_FORMS': '0', 'form-MAX_NUM_FORMS': '', 'form-0-field1':'good-value', … } formset = BracketInlineFormset(data) self.assertTrue(formset.is_valid()) However that doesn't work and raises the exception: ====================================================================== ERROR: testValid (appname.tests.StructureTestCase) ---------------------------------------------------------------------- Traceback (most recent call last): File "/paht/to/project/tests.py", line 494, in testValid formset = BracketInlineFormset(data) File "/path/to/django/forms/models.py", line 672, in __init__ self.instance = self.fk.rel.to() AttributeError: 'BracketInlineFormset' object has no attribute 'fk' ---------------------------------------------------------------------- The Django documentation (for formset validation) implies one can do this. How come this isn't working? How do I test the custom clean()/validation for my inline formset?

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• JavaFX: File upload to REST service / servlet fails because of missing boundary

  - by spa

  I'm trying to upload a file using JavaFX using the HttpRequest. For this purpose I have written the following function. function uploadFile(inputFile : File) : Void { // check file if (inputFile == null or not(inputFile.exists()) or inputFile.isDirectory()) { return; } def httpRequest : HttpRequest = HttpRequest { location: urlConverter.encodeURL("{serverUrl}"); source: new FileInputStream(inputFile) method: HttpRequest.POST headers: [ HttpHeader { name: HttpHeader.CONTENT_TYPE value: "multipart/form-data" } ] } httpRequest.start(); } On the server side, I am trying to handle the incoming data using the Apache Commons FileUpload API using a Jersey REST service. The code used to do this is a simple copy of the FileUpload tutorial on the Apache homepage. @Path("Upload") public class UploadService { public static final String RC_OK = "OK"; public static final String RC_ERROR = "ERROR"; @POST @Produces("text/plain") public String handleFileUpload(@Context HttpServletRequest request) { if (!ServletFileUpload.isMultipartContent(request)) { return RC_ERROR; } FileItemFactory factory = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(factory); List<FileItem> items = null; try { items = upload.parseRequest(request); } catch (FileUploadException e) { e.printStackTrace(); return RC_ERROR; } ... } } However, I get a exception at items = upload.parseRequest(request);: org.apache.commons.fileupload.FileUploadException: the request was rejected because no multipart boundary was found I guess I have to add a manual boundary info to the InputStream. Is there any easy solution to do this? Or are there even other solutions?

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• Java Play Mustache NPE Error

  - by zanedev

  We are getting a mustache play error in production (amazon linux EC2 AMI) but not in development (MACs) and we have tried upgrading the jvm, using the jdk instead, and changing from a tomcat deploy model to match our development environments as much as possible but nothing is working. Please any help would be greatly appreciated. We have lots of shared code in java and javascript using mustache and it would be a big deal to rewrite everything if we had to ditch mustache on the java side. 20:48:52,403 ERROR ~ @6al2dd0po Internal Server Error (500) for request GET /mystuff/people Execution exception (In {module:mustache-0.2}/app/play/modules/mustache/MustacheTags.java around line 32) NullPointerException occured : null play.exceptions.JavaExecutionException at play.templates.BaseTemplate.throwException(BaseTemplate.java:90) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:257) at play.templates.Template.render(Template.java:26) at play.templates.GroovyTemplate.render(GroovyTemplate.java:187) at play.mvc.results.RenderTemplate.<init>(RenderTemplate.java:24) at play.mvc.Controller.renderTemplate(Controller.java:660) at play.mvc.Controller.renderTemplate(Controller.java:640) at play.mvc.Controller.render(Controller.java:695) at controllers.MyStuff.people(MyStuff.java:183) at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:548) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:502) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:478) at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:473) at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161) at Invocation.HTTP Request(Play!) Caused by: java.lang.NullPointerException at play.modules.mustache.MustacheTags._template(MustacheTags.java:32) at play.modules.mustache.MustacheTags$_template.call(Unknown Source) at /app/views/User/people.html.(line:22) at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:232) ... 13 more

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• Getting a Specified Cast is not valid while importing data from Excel using Linq to SQL

  - by niceoneishere

  This is my second post. After learning from my first post how fantastic is to use Linq to SQL, I wanted to try to import data from a Excel sheet into my SQL database. First My Excel Sheet: it contains 4 columns namely ItemNo ItemSize ItemPrice UnitsSold I have a created a database table with the following fields table name ProductsSold Id int not null identity --with auto increment set to true ItemNo VarChar(10) not null ItemSize VarChar(4) not null ItemPrice Decimal(18,2) not null UnitsSold int not null Now I created a dal.dbml file based on my database and I am trying to import the data from excel sheet to db table using the code below. Everything is happening on click of a button. private const string forecast_query = "SELECT ItemNo, ItemSize, ItemPrice, UnitsSold FROM [Sheet1$]"; protected void btnUpload_Click(object sender, EventArgs e) { var importer = new LinqSqlModelImporter(); if (fileUpload.HasFile) { var uploadFile = new UploadFile(fileUpload.FileName); try { fileUpload.SaveAs(uploadFile.SavePath); if(File.Exists(uploadFile.SavePath)) { importer.SourceConnectionString = uploadFile.GetOleDbConnectionString(); importer.Import(forecast_query); gvDisplay.DataBind(); pnDisplay.Visible = true; } } catch (Exception ex) { Response.Write(ex.Source.ToString()); lblInfo.Text = ex.Message; } finally { uploadFile.DeleteFileNoException(); } } } // Now here is the code for LinqSqlModelImporter public class LinqSqlModelImporter : SqlImporter { public override void Import(string query) { // importing data using oledb command and inserting into db using LINQ to SQL using (var context = new WSDALDataContext()) { using (var myConnection = new OleDbConnection(base.SourceConnectionString)) using (var myCommand = new OleDbCommand(query, myConnection)) { myConnection.Open(); var myReader = myCommand.ExecuteReader(); while (myReader.Read()) { context.ProductsSolds.InsertOnSubmit(new ProductsSold() { ItemNo = myReader.GetString(0), ItemSize = myReader.GetString(1), ItemPrice = myReader.GetDecimal(2), UnitsSold = myReader.GetInt32(3) }); } } context.SubmitChanges(); } } } can someone please tell me where am I making the error or if I am missing something, but this is driving me nuts. When I debugged I am getting this error when casting from a number the value must be a number less than infinity I really appreciate it

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• FileNotFoundException Java

  - by Troels Hansen

  Hi, I'm trying to make a simple highscore system for a minesweeper game. However i keep getting a file not found exception, and i've tried to use the full path for the file aswell. package minesweeper; import java.io.*; import java.util.*; public class Highscore{ public static void submitHighscore(String difficulty) throws IOException{ int easy = 99999; int normal = 99999; int hard = 99999; //int newScore = (int) MinesweeperView.getTime(); int newScore = 10; File f = new File("Highscores.dat"); if (!f.exists()){ f.createNewFile(); } Scanner input = new Scanner(f); PrintStream output = new PrintStream(f); if (input.hasNextInt()){ easy = input.nextInt(); normal = input.nextInt(); hard = input.nextInt(); } output.flush(); if(difficulty.equals("easy")){ if (easy > newScore){ easy = newScore; } }else if (difficulty.equals("normal")){ if (normal > newScore){ normal = newScore; } }else if (difficulty.equals("hard")){ if (hard > newScore){ hard = newScore; } } output.println(easy); output.println(normal); output.println(hard); } //temporary main method used for debugging public static void main(String[] args) throws IOException { submitHighscore("easy"); } }

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• Iterating through Event Log Entry Collection, IndexOutOutOfBoundsException

  - by fjdumont

  Hello, in a service application I am iterating through the Windows application event log to parse Events in order react depanding on the entry message. In the case that the event log is full (Windows usually makes sure there is enough space by deleting old entries - this is configurable in the eventvwr.exe settings), the service always runs into an IndexOutOfBoundsException while iterating through the EventLog.Entries collection. No matter how I iterate (for-loop, using the collections enumerator, copying the collection into an array, ...), I can't seem to get rid of this ´bug´. Currently, I ensure that the log is not full in order to keep the service running by regularly deleting the last few item by parsing the event log file and deleting the last few nodes (Don't beat me up, I couldn't find a better alternative...). How can I iterate through the collection without trying to access already deleted entries? Is there probably a more elegant method? I am only trying to acces the logs written during the last x seconds (even LINQ failed to select those when the log is full - same exception), could this help? Thanks for any advice and hints Frank Edit: I forgot to mention that my assumption is the loops are accessing entries which are being deleted during iteration by Windows. Basically that is why I tried to clone the collection. Is there perhaps a way to lock the collection for a small amount of time for just my application?

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• C# / IronPython Interop with shared C# Class Library

  - by Adam Haile

  I'm trying to use IronPython as an intermediary between a C# GUI and some C# libraries, so that it can be scripted post compile time. I have a Class library DLL that is used by both the GUI and the python and is something along the lines of this: namespace MyLib { public class MyClass { public string Name { get; set; } public MyClass(string name) { this.Name = name; } } } The IronPython code is as follows: import clr clr.AddReferenceToFile(r"MyLib.dll") from MyLib import MyClass ReturnObject = MyClass("Test") Then, in C# I would call it as follows: ScriptEngine engine = Python.CreateEngine(); ScriptScope scope = null; scope = engine.CreateScope(); ScriptSource source = engine.CreateScriptSourceFromFile("Script.py"); source.Execute(scope); MyClass mc = scope.GetVariable<MyClass>("ReturnObject ") When I call this last bit of code, source.Execute(scope) runs returns successfully, but when I try the GetVariable call, it throw the following exception Microsoft.Scripting.ArgumentTypeException: expected MyClass , got MyClass So, you can see that the class names are exactly the same, but for some reason it thinks they are different. The DLL is in a different directory than the .py file (I just didn't bother to write out all the path setup stuff), could it be that there is an issue with the interpreter for IronPython seeing these objects as difference because it's somehow seeing them as being in a different context or scope?

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• Big trouble after app update. CoreData migration error

  - by MrBr

  this morning we had a big trouble with our iphone app. We had to even take it off the store. The thing is that we made real small changes to our xcdatamodel. We thought that the update process is automatically taking care about exchanging it the right way until we found out something like CoreData migration exists. We are using the UIManagedDocument to connect to the persistent store. How is it possible to exchange this file with the new one? While we were developing we just uninstalled the whole app from the device and then installed it again and everything worked. How can we simulate this process in the app store with updates? UPDATE I try to set the migration option like this _database = [[UIIManagedDocument alloc] init]; NSMutableDictionary *options = [[NSMutableDictionary alloc] init]; [options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption], _database.persistentStoreOptions = options; but the app is still crashing with ** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores. It cannot perform a save operation.'

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• Achieving Thread-Safety

  - by Smasher

  Question How can I make sure my application is thread-safe? Are their any common practices, testing methods, things to avoid, things to look for? Background I'm currently developing a server application that performs a number of background tasks in different threads and communicates with clients using Indy (using another bunch of automatically generated threads for the communication). Since the application should be highly availabe, a program crash is a very bad thing and I want to make sure that the application is thread-safe. No matter what, from time to time I discover a piece of code that throws an exception that never occured before and in most cases I realize that it is some kind of synchronization bug, where I forgot to synchronize my objects properly. Hence my question concerning best practices, testing of thread-safety and things like that. mghie: Thanks for the answer! I should perhaps be a little bit more precise. Just to be clear, I know about the principles of multithreading, I use synchronization (monitors) throughout my program and I know how to differentiate threading problems from other implementation problems. But nevertheless, I keep forgetting to add proper synchronization from time to time. Just to give an example, I used the RTL sort function in my code. Looked something like FKeyList.Sort (CompareKeysFunc); Turns out, that I had to synchronize FKeyList while sorting. It just don't came to my mind when initially writing that simple line of code. It's these thins I wanna talk about. What are the places where one easily forgets to add synchronization code? How do YOU make sure that you added sync code in all important places?

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• How to Update with LINQ?

  - by DaveDev

  currently, I'm doing an update similar to as follows, because I can't see a better way of doing it. I've tried suggestions that I've read in blogs but none work, such as http://msdn.microsoft.com/en-us/library/bb425822.aspx and http://weblogs.asp.net/scottgu/archive/2007/05/19/using-linq-to-sql-part-1.aspx Maybe these do work and I'm missing some point. Has anyone else had luck with them? // please note this isn't the actual code. // I've modified it to clarify the point I wanted to make // and also I didn't want to post our code here! public bool UpdateMyStuff(int myId, List<int> funds) { // get MyTypes that correspond to the ID I want to update IQueryable<MyType> myTypes = database.MyTypes.Where(xx => xx.MyType_MyId == myId); // delete them from the database foreach (db.MyType mt in myTypes) { database.MyTypes.DeleteOnSubmit(mt); } database.SubmitChanges(); // create a new row for each item I wanted to update, and insert it foreach (int fund in funds) { database.MyType mt = new database.MyType { MyType_MyId = myId, fund_id = fund }; database.MyTypes.InsertOnSubmit(mt); } // try to commit the insert try { database.SubmitChanges(); return true; } catch (Exception) { return false; throw; } } Unfortunately, there isn't a database.MyTypes.Update() method so I don't know a better way to do it. Can sombody suggest what I could do? Thanks. ..as a side note, why isn't there an Update() method?

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• Ruby TypeErrors involving `expected Data`

  - by Kenny Peng

  I've ran into situations where I have gotten these expected Data errors before, but they have always pointed to ActiveRecord not playing well with other libraries in the past. This piece of code: def load(kv_block, debug=false) # Converts a string block to a Hash using split kv_map = StringUtils.kv_array_to_hash(kv_block) # Loop through each key, value kv_map.each do |mem,val| # Format the member from camel case to underscore member = mem.camel_to_underscore() # If the object includes a method to set the key (i.e. the key # is a member of self), invoke the method, setting the value of # the member) if self.methods.include?(member.to_set_method_name()) then # Exception thrown here self.send(member.to_set_method_name(), val) # Else, check for the same case, this time for an instance variable elsif self.instance_variable_defined?(member.to_instance_var_name()) self.instance_variable_set(member.to_instance_var_name(), val) # Else, complain that the object doesn't understand the key with # respect to its class definition. else raise ArgumentError, "I don't know what to do with #{member}. #{self.class} does not have a member or function called #{member}" end end end produces the error wrong argument type #<Class:0x11a02088> (expected Data) (TypeError) in the each loop on the first if test. I've inspected a post-mortem debugging instance using rdebug, and running that line manually, it works without a hitch. Has anyone seen this error before and what's been your solution to it? I used to think it was ActiveRecord and other gems stomping on each other's definitions, but I removed any references to ActiveRecord and this still occurs.

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• Spring 3 MVC validation BindingResult doesn't contain any errors

  - by Travelsized

  I'm attempting to get a Spring 3.0.2 WebMVC project running with the new annotated validation support. I have a Hibernate entity annotated like this: @Entity @Table(name = "client") public class Client implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic(optional = false) @Column(name = "clientId", nullable = false) @NotEmpty private Integer clientId; @Basic(optional = false) @Column(name = "firstname", nullable = false, length = 45) @NotEmpty @Size(min=2, max=45) private String firstname; ... more fields, getters and setters } I've turned on mvc annotation support in my applicationContext.xml file: <mvc:annotation-driven /> And I have a method in my controller that responds to a form submission: @RequestMapping(value="/addClient.htm") public String addClient(@ModelAttribute("client") @Valid Client client, BindingResult result) { if(result.hasErrors()) { return "addClient"; } service.storeClient(client); return "clientResult"; } When my app loads in the server, I can see in the server log file that it loads a validator: 15 [http-8084-2] INFO org.hibernate.validator.util.Version - Hibernate Validator 4.0.2.GA The problem I'm having is that the validator doesn't seem to kick in. I turned on the debugger, and when I get into the controller method, the BindingResult contains 0 errors after I submit an empty form. (The BindingResult does show that it contains the Client object as a target.) It then proceeds to insert a record without an Id and throws an exception. If I fill out an Id but leave the name blank, it creates a record with the Id and empty fields. What steps am I missing to get the validation working?

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• Permission denied to access property 'toString'

  - by Anders

  I'm trying to find a generic way of getting the name of Constructors. My goal is to create a Convention over configuration framework for KnockoutJS My idea is to iterate over all objects in the window and when I find the contructor i'm looking for then I can use the index to get the name of the contructor The code sofar (function() { constructors = {}; window.findConstructorName = function(instance) { var constructor = instance.constructor; var name = constructors[constructor]; if(name !== undefined) { return name; } var traversed = []; var nestedFind = function(root) { if(typeof root == "function" || traversed[root]) { return } traversed[root] = true; for(var index in root) { if(root[index] == constructor) { return index; } var found = nestedFind(root[index]); if(found !== undefined) { return found; } } } name = nestedFind(window); constructors[constructor] = name; return name; } })(); var MyApp = {}; MyApp.Foo = function() { }; var instance = new MyApp.Foo(); console.log(findConstructorName(instance)); The problem is that I get a Permission denied to access property 'toString' Exception, and i cant even try catch so see which object is causing the problem Fiddle http://jsfiddle.net/4ZwaV/

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• ASP.NEt MVC 2 application error on IIS7 works fine on local machine

  - by aspCoolguy

  My ASP.NET MVC2 application is developed using 1. VS 2010 2. Linq To SQL for Models Here is Call controller code: namespace CallTrackMVC.Controllers { public class CallController : Controller { private CallTrackRepository repository; public CallController():this(new CallTrackRepository()) { } public CallController(CallTrackRepository newRepository) { repository = newRepository; } } } Error on IIS7 when browsing the Call Create page is NullReferenceException: Object reference not set to an instance of an object.] CallTrackMVC.Models.ExecOfficeDataContext..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Models\ExecOffice.designer.cs:71 CallTrackMVC.Controllers.CallController..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Controllers\CallController.cs:16 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +117 System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +247 System.Activator.CreateInstance(Type type, Boolean nonPublic) +106 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +102 [InvalidOperationException: **An error occurred when trying to create a controller of type 'CallTrackMVC.Controllers.CallController'. Make sure that the controller has a parameterless public constructor.**] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +541 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +85 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +165 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +80 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +389 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371 Code in Global.asax is protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); } Any suggestion would be a great help.

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• Running an RMI registry on one computer and connecting to it from another

  - by Hippopotamus

  Hello. I am doing a student assignment, using java RMI. I've programmed a simple RMI-server application that provides method which return some strings to the client. When I start the server on localhost and connect to it by client on the same computer, everything goes well. However, I am not able to do this between two computers on home network. The computers both have no trouble of connecting by a simple C program with similar functionality, so I guess the problem is with JVM here. I am binding the class to rmiregistry with try{ ComputeImpl R = new ComputeImpl(); Naming.rebind("rmi://localhost/ComputeService",R); } catch(Exception e){ System.out.println("Trouble: " +e); } And I'm doing the lookup for RMI registry in the client application with providing the argument while launching the application: StringBuffer rmi_address = new StringBuffer(); rmi_address.append("rmi://").append(args[1]).append("/ComputeService"); Compute R = (Compute) Naming.lookup(rmi_address.toString()); Is the problem with my code or with JVM? Thanks in advance.

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• How to easily map c++ enums to strings

  - by Roddy

  I have a bunch of enum types in some library header files that I'm using, and I want to have a way of converting enum values to user strings - and vice-versa. RTTI won't do it for me, because the 'user strings' need to be a bit more readable than the enumerations. A brute force solution would be a bunch of functions like this, but I feel that's a bit too C-like. enum MyEnum {VAL1, VAL2,VAL3}; String getStringFromEnum(MyEnum e) { switch e { case VAL1: return "Value 1"; case VAL2: return "Value 2"; case VAL1: return "Value 3"; default: throw Exception("Bad MyEnum"); } } I have a gut feeling that there's an elegant solution using templates, but I can't quite get my head round it yet. UPDATE: Thanks for suggestions - I should have made clear that the enums are defined in a third-party library header, so I don't want to have to change the definition of them. My gut feeling now is to avoid templates and do something like this: char * MyGetValue(int v, char *tmp); // implementation is trivial #define ENUM_MAP(type, strings) char * getStringValue(const type &T) \ { \ return MyGetValue((int)T, strings); \ } ; enum eee {AA,BB,CC}; - exists in library header file ; enum fff {DD,GG,HH}; ENUM_MAP(eee,"AA|BB|CC") ENUM_MAP(fff,"DD|GG|HH") // To use... eee e; fff f; std::cout<< getStringValue(e); std::cout<< getStringValue(f);

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