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• Php script running as scheduled task hangs - help!

  - by Ali

  Hi guys, I've built a php script that runs from the command line. It opens a connection into a pop3 email account and downloads all the emails and writes them to a database, and deletes them once downloaded. I have this script being called from the commandline by a bat file. in turn I have created a scheduled task which invokes the bat file every 5 minutes. The thing is that I have set the time out to zero for the fact that at times there could be emails with large attachments and the script actually downloads the attachments and stores them as raw files offline and the no timeout is so that the script doesnt die out during downloading. I've found that the program hangs sometimes and its a bit annoying at that - it always hangs are one point i.e. when negotiating the connection and getting connected to the mail server. And because the timeout is set to zero it seems to stay stuck up in taht position. And because of that the task is not run as its technically hung up. I want that the program should not timeout when downloading emails - however at the points where it is negotiating a connection or trying to connect to the mailserver there should be a timeout only at that point itself and not the rest of the program execution. How do I do this :(

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• I need a fast runtime expression parser

  - by Chris Lively

  I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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• How to upload files to server using JSP/Servlet?

  - by Thang Pham

  How can I upload files to server using JSP/Servlet? I tried this: <form action="upload" method="post"> <input type="text" name="description" /> <input type="file" name="file" /> <input type="submit" /> </form> However, I only get the file name, not the file content. When I add enctype="multipart/form-data" to the <form>, then request.getParameter() returns null. During research I stumbled upon Apache Common FileUpload. I tried this: FileItemFactory factory = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(factory); List items = upload.parseRequest(request); // This line is where it died. Unfortunately, the servlet threw an exception without a clear message and cause. Here is the stacktrace: SEVERE: Servlet.service() for servlet UploadServlet threw exception javax.servlet.ServletException: Servlet execution threw an exception at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:313) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:637)

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• How to get SimpleRpcClient.Call() to be a blocking call to achieve synchronous communication with RabbitMQ?

  - by Nick Josevski

  In the .NET version (2.4.1) of RabbitMQ the RabbitMQ.Client.MessagePatterns.SimpleRpcClient has a Call() method with these signatures: public virtual object[] Call(params object[] args); public virtual byte[] Call(byte[] body); public virtual byte[] Call(IBasicProperties requestProperties, byte[] body, out IBasicProperties replyProperties); The problem: With various attempts, the method still continues to not block where I expect it to, so it's unable ever handle the response. The Question: Am I missing something obvious in the setup of the SimpleRpcClient, or earlier with the IModel, IConnection, or even PublicationAddress? More Info: I've also tried various paramater configurations of the QueueDeclare() method too with no luck. string QueueDeclare(string queue, bool durable, bool exclusive, bool autoDelete, IDictionary arguments); Some more reference code of my setup of these: IConnection conn = new ConnectionFactory{Address = "127.0.0.1"}.CreateConnection()); using (IModel ch = conn.CreateModel()) { var client = new SimpleRpcClient(ch, queueName); var queueName = ch.QueueDeclare("t.qid", true, true, true, null); ch.QueueBind(queueName, "exch", "", null); //HERE: does not block? var replyMessageBytes = client.Call(prop, msgToSend, out replyProp); } Looking elsewhere: Or is it likely there's an issue in my "server side" code? With and without the use of BasicAck() it appears the client has already continued execution.

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• Scheduling algorithm optimized to execute during low usage periods.

  - by The Rook

  Lets say there is a Web Application serving mostly one country. Because of normal sleep habits website traffic follows a Sine wave, where 1 period lasts 24 hours and the lowest part of the wave is at about midnight. Is there a scheduling algorithm optimized to execute during low usage periods? I am thinking of this as a liquid that is "pored into" this sine wave to flatten out resource usage. A ideal algorithm would take the integral of this empty space. If the same tasks need to be run daily the amount of resources consumed by previous executions could be used to predict future usage by looking at the rate in which resource usage is increasing. By knowing the amount of resources required this algorithm could fill in this empty space while leaving as much buffer as possible on either side such that its interference was reduced as much as possible. It would also be possible to detect if there isn't enough resources before execution begins, this opens the door for a cloud to help out. Does anything like this exist? Or should I build it into an existing scheduler like quartz and make it open source?

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• How to Resolve a Transformation Service with BRE that occurs after an Orchestration in an Itinerary?

  - by Maxime Labelle

  In trying to implement simple integration patterns with Biztalk ESB Toolkit 2.0, I'm facing a problem trying to resolve a Transformation Itinerary Service that occurs after an Orchestration. I'm using the BRE Resolver to execute rules that need to inspect the Context Message Type property to determine the appropriate map to use. However, once the message reaches the step in the Itinerary associated with the Transformation Service, the map fails to execute. From careful investigation, it appears that the message type is not supplied to the "Resolution" object that is used internally by the BRE resolver. Indeed, since the message leaving the preceding Orchestration is typed System.Xml.XmlDocument, the type of the message is "demoted" from the context. By tracking rules engine execution, I can observe that the type of the message is indeed lost when reaching the BRE resolver. The type of the message is empty, whereas the strongly-typed of the document is Microsoft.XLANGs.BaseTypes.Any. The Orchestration service that I use is taken straight from the samples that ship with ESB Toolkit 2.0. Is there a way to perform Context-Based BRE resolution after an Orchestration in an Itinerary?

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• How do I display java.lang.* object allocations in Eclipse profiler?

  - by Martin Wickman

  I am profiling an application using the Eclipse profiler. I am particularly interested in number of allocated object instances of classes from java.lang (for instance java.lang.String or java.util.HashMap). I also want to know stuff like number of calls to String.equals() etc. I use the "Object Allocations" tab and I shows all classes in my application and a count. It also shows all int[], byte[], long[] etc, but there is no mention of any standard java classes. For instance, this silly code: public static void main(String[] args) { Object obj[] = new Object[1000]; for (int i = 0; i < 1000; i++) { obj[i] = new StringBuffer("foo" + i); } System.out.println (obj[30]); } Shows up in the Object Allocations tab as 7 byte[]s, 4 char[]s and 2 int[]s. It doesn't matter if I use 1000 or 1 iterations. It seems the profiler simply ignores everything that is in any of the java.* packages. The same applies to Execution Statistics as well. Any idea how to display instances of java.* in the Eclipse Profiler?

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• Correct way to do timer function in Python

  - by bwawok

  Hi. I have a GUI application that needs to do something simple in the background (update a wx python progress bar, but that doesn't really matter). I see that there is a threading.timer class.. but there seems to be no way to make it repeat. So if I use the timer, I end up having to make a new thread on every single execution... like : import threading import time def DoTheDew(): print "I did it" t = threading.Timer(1, function=DoTheDew) t.daemon = True t.start() if __name__ == '__main__': t = threading.Timer(1, function=DoTheDew) t.daemon = True t.start() time.sleep(10) This seems like I am making a bunch of threads that do 1 silly thing and die.. why not write it as : import threading import time def DoTheDew(): while True: print "I did it" time.sleep(1) if __name__ == '__main__': t = threading.Thread(target=DoTheDew) t.daemon = True t.start() time.sleep(10) Am I missing some way to make a timer keep doing something? Either of these options seems silly... I am looking for a timer more like a java.util.Timer that can schedule the thread to happen every second... If there isn't a way in Python, which of my above methods is better and why?

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• CCNet exception during build of vs2010 project

  - by sonee

  We have two build machines. Lately, we've migrated our projects to vs2010 from vs2005. But the problem is that one of the machines occurs error during build. Another machine works well, but just one machine shows error. The differences between the machines are os and computer spec. The machine which is working well is installed windows server 2003 and the other is windows7. the error message is unhandled exception: System.NullReferenceException: Microsoft.VisualStudio.Shell.ThreadHelper.InvokeOnUIThread(InvokableBase invokable) Microsoft.VisualStudio.Shell.ThreadHelper.Invoke(Action action)Microsoft.VisualStudio.Project.VS.Implementation.VSShellServices.InvokeOnUIThread(Action method) Microsoft.VisualStudio.Project.VisualC.VCProjectEngine.ApartmentMarshaler.Invoke(Action method) Microsoft.VisualStudio.Project.VisualC.VCProjectEngine.VCConfigBuildJob.BuildCompleted(BuildSubmission ar) Microsoft.VisualStudio.Project.Contracts.Implementation.BuildProjectBase.BuildCompletedCallbackManager.BuildCompleted(BuildSubmission buildSubmission) Microsoft.Build.Execution.BuildSubmission.<CheckForCompletion>b__0(Object state) System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state) System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() System.Threading.ThreadPoolWorkQueue.Dispatch() System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() Curiously enough, when I run building project in command line on the machine which occurs error, it works well. The machine just shows error when launched by ccnet. I've installed latest version of ccnet to all machines. Is there anybody who faced like this problem?

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• javascript error handeling

  - by pankaj

  I have a javascript function for checking errors which i am callin on OnClicentClick event of a button. Once it catch a error i want to stop execution of click event . But in my case it always it always executes the onclick event. Following is my function: function DisplayError() { if (document.getElementById('<%=txtPassword.ClientID %>').value.length < 6 || document.getElementById('<%=txtPassword.ClientID %>').value.length > 12) { document.getElementById('<%=lblError.ClientID %>').innerText = "Password length must be between 6 to 12 characters"; return false; } var str = <%=PhoneNumber()%>; if(str.length <10) { alert('<%=phoneNum%>'.length); document.getElementById('<%=lblError.ClientID %>').innerText = "Phone Number not in correct format"; return false; } } button html code: <asp:Button runat="server" Text="Submit" ID="btnSubmit" ValidationGroup="submit" onclick="btnSubmit_Click" OnClientClick="DisplayError()"/> It should not execute the button click event once it satisfies any of the IF condition in javascript function.

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• Updating Android Tab Icons

  - by lnediger

  I have an activity which has a TabHost containing a set of TabSpecs each with a listview containing the items to be displayed by the tab. When each TabSpec is created, I set an icon to be displayed in the tab header. The TabSpecs are created in this way within a setupTabs() method which loops to create the appropriate number of tabs: TabSpec ts = mTabs.newTabSpec("tab"); ts.setIndicator("TabTitle", iconResource); ts.setContent(new TabHost.TabContentFactory( { public View createTabContent(String tag) { ... } }); mTabs.addTab(ts); There are a couple instances where I want to be able to change the icon which is displayed in each tab during the execution of my program. Currently I am deleting all the tabs, and calling the above code again to re-create them. mTabs.getTabWidget().removeAllViews(); mTabs.clearAllTabs(true); setupTabs(); Is there a way to replace the icon that is being displayed without deleting and re-creating all of the tabs?

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• Client-Side Dynamic Removal of <script> Tags in <head>

  - by merv

  Is it possible to remove script tags in the <head> of an HTML document client-side and prior to execution of those tags? On the server-side I am able to insert a <script> above all other <script> tags in the <head>, except one, and I would like to be able to remove all subsequent scripts. I do not have the ability to remove <script> tags from the server side. What I've tried: (function (c,h) { var i, s = h.getElementsByTagName('script'); c.log("Num scripts: " + s.length); i = s.length - 1; while(i > 1) { h.removeChild(s[i]); i -= 1; } })(console, document.head); However, the logged number of scripts comes out to only 1, since (as @ryan pointed out) the code is being executed prior to the DOM being ready. Although wrapping the code above in a document.ready event callback does enable proper calculation of the number of <script> tags in the <head>, waiting until the DOM is ready fails to prevent the scripts from loading. Is there a reliable means of manipulating the HTML prior to the DOM being ready? Background If you want more context, this is part of an attempt to consolidate scripts where no option for server-side aggregation is available. Many of the JS libraries being loaded are from a CMS with limited configuration options. The content is mostly static, so there is very little concern about manually aggregating the JavaScript and serving it from a different location. Any suggestions for alternative applicable aggregation techniques would also be welcome.

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• SqlCeResultSet Problem

  - by Vlad

  Hello, I have a SmartDevice project (.NetCF 2.0) configured to be tested on the USA Windows Mobile 5.0 Pocket PC R2 Emulator. My project uses SqlCe 3.0. Understanding that a SmartDevice project is "more carefull" with the device's memory I am using SqlCeResultSets. The result sets are strongly typed, autogenerated by Visual Studio 2008 using the custom tool MSResultSetGenerator. The problem I am facing is that the result set does not recognize any column names. The autogenerated code for the fields does not work. In the client code I am using InfoResultSet rs = new InfoResultSet(); rs.Open(); rs.ReadFirst(); string myFormattedDate = rs.MyDateColumn.ToString("dd/MM/yyyy"); When the execution on the emulator reaches the rs.MyDateColumn the application throws an System.IndexOutOfRangeException. Investigating the stack trace at System.Data.SqlServerCe.FieldNameLookup.GetOrdinal() at System.Data.SqlServerCe.SqlCeDataReader.GetOrdinal() I've tested the GetOrdinal method (in my autogenerated class that inherits SqlCeResultSet): this.GetOrdinal("MyDateColumn"); // throws an exception this.GetName(1); // returns "MyDateColumn" this.GetOrdinal(this.GetName(1)); //throws an exception :) [edit added] The table exists and it's filled with data. Using typed DataSets works like a charm. Regenerating the SqlCeResultSet does not solve the issue, the problem remains. The problem basically is that I am not able to access a column by it's name. The data can be accessed trough this.GetDateTime(1)using the column ordinal. The application fails executing this.GetOrdinal("MyDateColumn"). Also I have updated Visual Studio 2008 to Service Pack 1. Additionaly I am developing the project on a virtual machine with Windows XP SP 2, but in my opinion if the medium is virtual or not should have no effect on the developing. Am I doing something wrong or am I missing something? Thank you.

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• Personalized UIView created with Interface Builder

  - by Malox

  I need to project a personalized UIView with a UIImageView and 3 UILabel. I need to allocate more of this view because I want put it into a UIScrollView. I would avoid to generate the view programatically because it's difficult and boring design it. My idea is to create a new class that extends UIView and design it with interface builder. For example my Personalized View code is like that: #import <UIKit/UIKit.h> @interface PersonalizedPreview : UIView { IBOutlet UIImageView *image; IBOutlet UILabel *first_label; IBOutlet UILabel *second_label; IBOutlet UILabel *third_label; } -(void) setImage:(UIImage *)image; @property (nonatomic, retain) IBOutlet UIImageView *image; @property (nonatomic, retain) IBOutlet UILabel *label; .... @end I would create an associated xib file for this view and initialize it simply specifing the xib file. Note that I don't want create a specific ViewController for this view and PersonalizedView is instantiate at runtime not when the app runs, moreover I don't know how many PersonalizedView I will instantiate, it depends on runtime execution. Anyone can help me? Thank you very much.

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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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• Returning data from SQL Server reporting web service call

  - by user79339

  Hi, I am generating a report that contains the version number. The version number is stored in the DB and retrieved/incremented as part of the report generation. The only problem is, I am calling SSRS via a web service call, which returns the generated report as a byte array. Is there any way to get the version number out of this generated report? For example to display a dialog that says "You generated Status Report, Version number 3". I tried passing in an output parameter and setting it inside the storedproc. Its modified when i execute it in sql management studio, but not in the reporting studio. Or atleast i can't seem to bind to the modified, post execution value (using expression "=Parameters!ReportVersion.Value"). Of course, I could get/increment the version number from database myself before calling the SSRS webservice and pass it along as a parameter to the Report, but that might cause concurrancy problems. On the whole, it just seems neater for the storedproc to access/generate a version number and return it to the ReportingEngine, which will generate the report with the version number and return the updated version number to the WebService client. Any thoughts/Ideas?

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• SQL Server service broker reporting as off when I have written a query to turn it on

  - by dotnetdev

  I have made a small ASP.NET website. It uses sqlcachedependency The SQL Server Service Broker for the current database is not enabled, and as a result query notifications are not supported. Please enable the Service Broker for this database if you wish to use notifications. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidOperationException: The SQL Server Service Broker for the current database is not enabled, and as a result query notifications are not supported. Please enable the Service Broker for this database if you wish to use notifications. Source Error: Line 12: System.Data.SqlClient.SqlDependency.Start(connString); This is the erroneous line in my global.asax. However, in sql server (2005), I enabled service broker like so (I connect and run the SQL Server service when I debug my site): ALTER DATABASE mynewdatabase SET ENABLE_BROKER with rollback immediate And this was successful. What am I missing? I am trying to use sql caching dependency and have followed all procedures. Thanks

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• Thread-safty of boost RNG

  - by Maciej Piechotka

  I have a loop which should be nicely pararellized by insering one openmp pragma: boost::normal_distribution<double> ddist(0, pow(retention, i - 1)); boost::variate_generator<gen &, BOOST_TYPEOF(ddist)> dgen(rng, ddist); // Diamond const std::uint_fast32_t dno = 1 << i - 1; // #pragma omp parallel for for (std::uint_fast32_t x = 0; x < dno; x++) for (std::uint_fast32_t y = 0; y < dno; y++) { const std::uint_fast32_t diff = size/dno; const std::uint_fast32_t x1 = x*diff, x2 = (x + 1)*diff; const std::uint_fast32_t y1 = y*diff, y2 = (y + 1)*diff; double avg = (arr[x1][y1] + arr[x1][y2] + arr[x2][y1] + arr[x2][y2])/4; arr[(x1 + x2)/2][(y1 + y2)/2] = avg + dgen(); } (unless I make an error each execution does not depend on others at all. Sorry that not all of code is inserted). However my question is - are boost RNG thread-safe? They seems to refer to gcc code for gcc so even if gcc code is thread-safe it may not be the case for other platforms.

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• PHP file upload issue

  - by Varun

  I am working on a PHP based, ticket management system. While creating a ticket, one can upload an attachment. I want to put a limit (say 10 MB) per file upload. To implement this I plan the following- 1. In php.ini set post_max_size = 10M 2.In PHP script which receives the POST- Since the file is larger than post_max_size, $_FILES[] will be empty. But I can still check the content-length header and discard the upload, if size more than 10M. While testing this I tried uploading a file of 1 GB and analysed the http traffic and this is what I found. - the entire 1 GB data is first uploaded to a to the server temporarily and discarded once the http request completes. Though I couldn't exactly find out where the file was getting saved(as it was not there in the temporary directory in the server.), but my http traffic analyzer showed that the browser did send 1 GB data to the server. - the PHP script execution started only after completion of the http request(i.e after uploading the entire 1 GB) Now I have 2 concerns: a) People may exploit my server bandwidth by trying to upload large file, which I will have to discard anyways. b) Even worse, if someone starts uploading a huge file (say 100 GB), entire 100 GB data is first uploaded to the server temporarily, that means for that period, it will consume that much of memory on my server. What's the common solution for this. Am I missing something here?

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• JavaScript window object element properties

  - by Timothy

  A coworker showed me the following code and asked me why it worked. <span id="myspan">Do you like my hat?</span> <script type="text/javascript"> var spanElement = document.getElementById("myspan"); alert("Here I am! " + spanElement.innerHTML + "\n" + myspan.innerHTML); </script> I explained that a property is attached to the window object with the name of the element's id when the browser parses the document which then contains a reference to the appropriate dom node. It's sort of as if window.myspan = document.getElementById("myspan") is called behind the scenes as the page is being rendered. The ensuing discussion we had raised a few of questions: The window object and most of the DOM are not part of the official JavaScript/ECMA standards, but is the above behavior documented in any other official literature, perhaps browser-related? The above works in a browser (at least the main contenders) because there is a window object, but fails in something like rhino. Is writing code that relys on this considered bad practice because it makes too many assumptions about the execution environment? Are there any browsers in which the above would fail, or is this considered standard behavior across the board? Does anyone here know the answers to those questions and would be willing to enlighten me? I tried a quick internet search, but I admit I'm not sure how to even properly phrase the query. Pointers to references and documentation are welcome.

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• Using LINQ to map dynamically (or construct projections)

  - by CodeGrue

  I know I can map two object types with LINQ using a projection as so: var destModel = from m in sourceModel select new DestModelType {A = m.A, C = m.C, E = m.E} where class SourceModelType { string A {get; set;} string B {get; set;} string C {get; set;} string D {get; set;} string E {get; set;} } class DestModelType { string A {get; set;} string C {get; set;} string E {get; set;} } But what if I want to make something like a generic to do this, where I don't know specifically the two types I am dealing with. So it would walk the "Dest" type and match with the matching "Source" types.. is this possible? Also, to achieve deferred execution, I would want it just to return an IQueryable. For example: public IQueryable<TDest> ProjectionMap<TSource, TDest>(IQueryable<TSource> sourceModel) { // dynamically build the LINQ projection based on the properties in TDest // return the IQueryable containing the constructed projection } I know this is challenging, but I hope not impossible, because it will save me a bunch of explicit mapping work between models and viewmodels.

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• Do database engines other than SQL Server behave this way?

  - by Yishai

  I have a stored procedure that goes something like this (pseudo code) storedprocedure param1, param2, param3, param4 begin if (param4 = 'Y') begin select * from SOME_VIEW order by somecolumn end else if (param1 is null) begin select * from SOME_VIEW where (param2 is null or param2 = SOME_VIEW.Somecolumn2) and (param3 is null or param3 = SOME_VIEW.SomeColumn3) order by somecolumn end else select somethingcompletelydifferent end All ran well for a long time. Suddenly, the query started running forever if param4 was 'Y'. Changing the code to this: storedprocedure param1, param2, param3, param4 begin if (param4 = 'Y') begin set param2 = null set param3 = null end if (param1 is null) begin select * from SOME_VIEW where (param2 is null or param2 = SOME_VIEW.Somecolumn2) and (param3 is null or param3 = SOME_VIEW.SomeColumn3) order by somecolumn end else select somethingcompletelydifferent And it runs again within expected parameters (15 seconds or so for 40,000+ records). This is with SQL Server 2005. The gist of my question is this particular "feature" specific to SQL Server, or is this a common feature among RDBMS' in general that: Queries that ran fine for two years just stop working as the data grows. The "new" execution plan destroys the ability of the database server to execute the query even though a logically equivalent alternative runs just fine? This may seem like a rant against SQL Server, and I suppose to some degree it is, but I really do want to know if others experience this kind of reality with Oracle, DB2 or any other RDBMS. Although I have some experience with others, I have only seen this kind of volume and complexity on SQL Server, so I'm curious if others with large complex databases have similar experience in other products.

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• Memory leaks while using array of double

  - by Gacek

  I have a part of code that operates on large arrays of double (containing about 6000 elements at least) and executes several hundred times (usually 800) . When I use standard loop, like that: double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... } The memory usage rises for about 40MB (from 40MB at the beggining of the loop, to the 80MB at the end). When I force to use the garbage collector to execute at every iteration, the memory usage stays at the level of 40MB (the rise is unsignificant). double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... GC.Collect() } But the execution time is 3 times longer! (it is crucial) How can I force the C# to use the same area of memory instead of allocating new ones? Note: I have the access to the code of someObject class, so if it would be needed, I can change it.

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• Program structure in long running data processing python script

  - by fmark

  For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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• Providing custom database functionality to custom asp.net membership provider

  - by IrfanRaza

  Hello friends, I am creating custom membership provider for my asp.net application. I have also created a separate class "DBConnect" that provides database functionality such as Executing SQL statement, Executing SPs, Executing SPs or Query and returning SqlDataReader and so on... I have created instance of DBConnect class within Session_Start of Global.asax and stored to a session. Later using a static class I am providing the database functionality throughout the application using the same single session. In short I am providing a single point for all database operations from any asp.net page. I know that i can write my own code to connect/disconnect database and execute SPs within from the methods i need to override. Please look at the code below - public class SGI_MembershipProvider : MembershipProvider { ...... public override bool ChangePassword(string username, string oldPassword, string newPassword) { if (!ValidateUser(username, oldPassword)) return false; ValidatePasswordEventArgs args = new ValidatePasswordEventArgs(username, newPassword, true); OnValidatingPassword(args); if (args.Cancel) { if (args.FailureInformation != null) { throw args.FailureInformation; } else { throw new Exception("Change password canceled due to new password validation failure."); } } ..... //Database connectivity and code execution to change password. } .... } MY PROBLEM - Now what i need is to execute the database part within all these overriden methods from the same database point as described on the top. That is i have to pass the instance of DBConnect existing in the session to this class, so that i can access the methods. Could anyone provide solution on this. There might be some better techniques i am not aware of that. The approach i am using might be wrong. Your suggessions are always welcome. Thanks for sharing your valuable time.

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