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  • Handling large (object) datasets with PHP

    - by Aron Rotteveel
    I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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  • Handling very large lists of objects without paging?

    - by user246114
    Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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  • Does rails do a rollback if I use begin...rescue?

    - by codeman73
    I'd like to add a begin...rescue block to one of my controllers create method, in order to log better info and construct the correct error message to return to the client. Does the rescue in any way 'interrupt' the rollback process? I'm assuming rails automatically does a rollback. When does it happen? Has it already happened by the time I get in the rescue clause? I'm using mySQL on Dreamhost and I think they use innoDB.

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  • Basic Python: Exception raising and local variable scope / binding

    - by SuperJdynamite
    I have a basic "best practices" Python question. I see that there are already StackOverflow answers tangentially related to this question but they're mired in complicated examples or involve multiple factors. Given this code: #!/usr/bin/python def test_function(): try: a = str(5) raise b = str(6) except: print b test_function() what is the best way to avoid the inevitable "UnboundLocalError: local variable 'b' referenced before assignment" that I'm going to get in the exception handler? Does python have an elegant way to handle this? If not, what about an inelegant way? In a complicated function I'd prefer to avoid testing the existence of every local variable before I, for example, printed debug information about them.

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  • Ruby xml rpc error handling

    - by stel
    I have a model class Car @@RPCServer = XMLRPC::Client.new("localhost", "/", 8080) def self.count @@RPCServer.call("cars.count") end end If server is not running on localhost:8080 I've got a Errno::ECONNREFUSED error. I want to display an error message to user, how can a handle this error?

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  • Mapping the System.Exception with FaultException

    - by user357342
    I have used exception sheilding feature of application block, to map System.Exception with class that is marked as DataContract. It works very well. But When I have mapped the System.Exception with FaultException, I got the below error message. "An error has occurred while consuming this service. Please contact your administrator for more information. Error ID: fe2d28b5-8d26-430e-baf4-fe4b39da853c" Please let me know whether I can map the System.Exception with FaultException

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  • Handling multiple accounts in Android app

    - by bebeTech
    I would like to build an application that caters for multiple accounts (eg. home, work) and account types (e.g. ISP, VoIP, Mobile). Essentially, I would like to get the user to create the accounts they want and then have all the accounts listed on the start page grouped by type. For example: ISP: - Home - Work Mobile: - Mum - Dad When you click on the account, it would take you to another screen where I do a bunch of calcs and display the results. I currently do this via multiple apps but am looking at consolidating into the one app. I am just not sure where to start or how I go about achieving this? The way the Contacts app works is a good example of what I am wanting to do.

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  • WPF Event Handler in Another Class

    - by Nathan Tornquist
    I have built a series of event handlers for some custom WPF controls. The event handles format the text displayed when the user enters or leaves a textbox based on the type of data contained (Phone number, zip code, monetary value, etc.) Right now I have all of the events locally in the C# code directly attached to the xaml. Because I have developed a could controls, this means that the logic is repeated a lot, and if I want to change the program-wide functionality I would have to make changes everywhere the event code is located. I am sure there is a way to put all of my event handlers in a single class. Can anyone help point me in the correct direction? I saw this article: Event Handler located in different class than MainWindow But I'm not sure if it directly relates to what I'm doing. I would rather make small changes to the existing logic that I have, as it works, then rewrite everything into commands. I would essentially like to something like this if possible: LostFocus="ExpandedTextBoxEvents.TextBox_LostFocus" It is easy enough to do something like this: private void TextBoxCurrencyGotFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyGotFocus(sender, e); } private void TextBoxCurrencyLostFocus(object sender, RoutedEventArgs e) { ExpandedTextBoxEvents.TextBoxCurrencyLostFocus(sender, e); } But that is less elegant.

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  • LINQ to Entites: How should I handle System.InvalidOperationException when checking for existance of

    - by chris
    I have a many-to-one relationship that users can edit via checkboxes. PK of Foo is ID, and fid contains the id from the checkbox. I'm checking to see if an element exists with: Foo ent; try { ent = ctx.Foo.First(f => f.ID == fid); } catch (System.InvalidOperationException ioe) { ent = new Foo(); } It seems to me that I should be able to do this without throwing an exception. What would be the best way to do this?

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  • In Asp.net i'm not able to catch any exception properly?

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • Handling static files with Django / lighttpd

    - by ptikobj
    I know that there is already a question (actually some more) about this, but the answers to them didn't help me out very much, as I am pretty new to lighttpd. I have one folder which contains .pdf-files. When doing a HttpResponseRedirect to the locations of one of those .pdf-files, the user should be able to download the .pdf file (or view it in the browser). Right now, Django just redirects to my "home" html page, without showing any pdf-file. Somehow, I will have to tell lighttpd that Django shouldn't handle this directory anymore. Is this the only thing I need to do? If yes, how should i do it?

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  • Distinguishing between failure and end of file in read loop

    - by celtschk
    The idiomatic loop to read from an istream is while (thestream >> value) { // do something with value } Now this loop has one problem: It will not distinguish if the loop terminated due to end of file, or due to an error. For example, take the following test program: #include <iostream> #include <sstream> void readbools(std::istream& is) { bool b; while (is >> b) { std::cout << (b ? "T" : "F"); } std::cout << " - " << is.good() << is.eof() << is.fail() << is.bad() << "\n"; } void testread(std::string s) { std::istringstream is(s); is >> std::boolalpha; readbools(is); } int main() { testread("true false"); testread("true false tr"); } The first call to testread contains two valid bools, and therefore is not an error. The second call ends with a third, incomplete bool, and therefore is an error. Nevertheless, the behaviour of both is the same. In the first case, reading the boolean value fails because there is none, while in the second case it fails because it is incomplete, and in both cases EOF is hit. Indeed, the program above outputs twice the same line: TF - 0110 TF - 0110 To solve this problem, I thought of the following solution: while (thestream >> std::ws && !thestream.eof() && thestream >> value) { // do something with value } The idea is to detect regular EOF before actually trying to extract the value. Because there might be whitespace at the end of the file (which would not be an error, but cause read of the last item to not hit EOF), I first discard any whitespace (which cannot fail) and then test for EOF. Only if I'm not at the end of file, I try to read the value. For my example program, it indeed seems to work, and I get TF - 0100 TF - 0110 So in the first case (correct input), fail() returns false. Now my question: Is this solution guaranteed to work, or was I just (un-)lucky that it happened to give the desired result? Also: Is there a simpler (or, if my solution is wrong, a correct) way to get the desired result?

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  • Exceptions over remote methods

    - by Andrei Vajna II
    What are the best practices for exceptions over remote methods? I'm sure that you need to handle all exceptions at the level of a remote method implementation, because you need to log it on the server side. But what should you do afterwards? Should you wrap the exception in a RemoteException (java) and throw it to the client? This would mean that the client would have to import all exceptions that could be thrown. Would it be better to throw a new custom exception with fewer details? Because the client won't need to know all the details of what went wrong. What should you log on the client? I've even heard of using return codes(for efficiency maybe?) to tell the caller about what happened. The important thing to keep in mind, is that the client must be informed of what went wrong. A generic answer of "Something failed" or no notification at all is unacceptable. And what about runtime (unchecked) exceptions?

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  • Centralizing Messagebox handling for application

    - by DRapp
    I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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  • Window resolution handling without javascript

    - by Sai Sasdhar
    Is there any CSS property to deal window resolution. I created a HTML page taking total resolution width as 1424px.When I open it on different resolution I see a scroll bar & resolution of HTML does not adjust automatically. I don't want the scrollbar to be seen in maximized size of the page. Is it possible without using javascript.At the same time how to increase the resolution when itself is created in lower res.

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  • Do you catch expected exceptions in the controller or business service of your asp.net mvc application

    - by Pascal
    I am developing an asp.net mvc application where user1 could delete data records which were just loaded before by user2. User2 either changes this non-existent data record (Update) or is doing an insert with this data in another table that a foreign-key constraint is violated. Where do you catch such expected exceptions? In the Controller of your asp.net mvc application or in the business service? Just a sidenote: I only catch the SqlException here if its a ForeignKey constraint exception to tell the user that another user has deleted a certain parent record and therefore he can not create the testplan. But this code is not fully implemented yet! Controller:   public JsonResult CreateTestplan(Testplan testplan)   {    bool success = false;    string error = string.Empty;    try   {    success = testplanService.CreateTestplan(testplan);    }   catch (SqlException ex)    {    error = ex.Message;    }    return Json(new { success = success, error = error }, JsonRequestBehavior.AllowGet);   } OR Business service: public Result CreateTestplan(Testplan testplan) { Result result = new Result(); try { using (var con = new SqlConnection(_connectionString)) using (var trans = new TransactionScope()) { con.Open(); _testplanDataProvider.AddTestplan(testplan); _testplanDataProvider.CreateTeststepsForTestplan(testplan.Id, testplan.TemplateId); trans.Complete(); result.Success = true; } } catch (SqlException e) { result.Error = e.Message; } return result; } then in the Controller: public JsonResult CreateTestplan(Testplan testplan)   {    Result result = testplanService.CreateTestplan(testplan);       return Json(new { success = result.success, error = result.error }, JsonRequestBehavior.AllowGet);   }

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  • .net exception pool

    - by javier
    I want to create a mecanism in a large .net application to handle all the exceptions in the application, and to save the error messages (in db or log file) so these errors can be fixed, and so we are aware of the problems in the application. Does anyone know a good way of creating a library to handle and process all the exceptions?. Are there any tools around that can simplify my task. What aproach would you suggest me to take.... If you previously implemented something similar to what I want to do, I do want to heard from you Thanks all

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  • Perl TCP Server handling multiple Client connections

    - by Matt
    I'll preface this by saying I have minimal experience with both Perl and Socket programming, so I appreciate any help I can get. I have a TCP Server which needs to handle multiple Client connections simultaneously and be able to receive data from any one of the Clients at any time and also be able to send data back to the Clients based on information it's received. For example, Client1 and Client2 connect to my Server. Client2 sends "Ready", the server interprets that and sends "Go" to Client1. The following is what I have written so far: my $sock = new IO::Socket::INET { LocalHost => $host, // defined earlier in code LocalPort => $port, // defined earlier in code Proto => 'tcp', Listen => SOMAXCONN, Reuse => 1, }; die "Could not create socket $!\n" unless $sock; while ( my ($new_sock,$c_addr) = $sock->accept() ) { my ($client_port, $c_ip) = sockaddr_in($c_addr); my $client_ipnum = inet_ntoa($c_ip); my $client_host = ""; my @threads; print "got a connection from $client_host", "[$client_ipnum]\n"; my $command; my $data; while ($data = <$new_sock>) { push @threads, async \&Execute, $data; } } sub Execute { my ($command) = @_; // if($command) = "test" { // send "go" to socket1 print "Executing command: $command\n"; system($command); } I know both of my while loops will be blocking and I need a way to implement my accept command as a thread, but I'm not sure the proper way of writing it.

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  • Proper exceptions to use for nulls

    - by user200295
    In the following example we have two different exceptions we want to communicate. //constructor public Main(string arg){ if(arg==null) throw new ArgumentNullException("arg"); Thing foo=GetFoo(arg); if(foo==null) throw new NullReferenceException("foo is null"); } Is this the proper approach for both exception types?

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  • Handling multiple media queries in Sass with Twitter Bootstrap

    - by Keith
    I have a Sass mixin for my media queries based on Twitter Bootstrap's responsive media queries: @mixin respond-to($media) { @if $media == handhelds { /* Landscape phones and down */ @media (max-width: 480px) { @content; } } @else if $media == small { /* Landscape phone to portrait tablet */ @media (max-width: 767px) {@content; } } @else if $media == medium { /* Portrait tablet to landscape and desktop */ @media (min-width: 768px) and (max-width: 979px) { @content; } } @else if $media == large { /* Large desktop */ @media (min-width: 1200px) { @content; } } @else { @media only screen and (max-width: #{$media}px) { @content; } } } And I call them throughout my SCSS file like so: .link { color:blue; @include respond-to(medium) { color: red; } } However, sometimes I want to style multiple queries with the same styles. Right now I'm doing them like this: .link { color:blue; /* this is fine for handheld and small sizes*/ /*now I want to change the styles that are cascading to medium and large*/ @include respond-to(medium) { color: red; } @include respond-to(large) { color: red; } } but I'm repeating code so I'm wondering if there is a more concise way to write it so I can target multiple queries. Something like this so I don't need to repeat my code (I know this doesn't work): @include respond-to(medium, large) { color: red; } Any suggestions on the best way to handle this?

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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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  • unhandled errors in php

    - by lexus
    How can I know during runtime that my code threw a Warning? example try { echo (25/0); } catch (exception $exc) { echo "exception catched"; } throws a "Warning: Division by zero" error that i can not handle on my code.

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