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  • Can a sub-procedure procedure lock and modify the same rows FOR UPDATE that its calling procedure al

    - by RenderIn
    Will the following code lead to a deadlock or should it work without any problem? I've got something similar and it's working but I didn't think it would. I thought the parent procedure's lock would have resulted in a deadlock for the child procedure but it doesn't seem to be. If it works, why? My guess is that the nested FOR UPDATE is not running into a deadlock because it's smart enough to realize that it is being called by the same procedure that has the current lock. Would this be a deadlock if FOO_PROC was not a nested procedure? DECLARE FOO_PROC(c_someName VARCHAR2) as cursor c1 is select * from awesome_people where person_name = c_someName FOR UPDATE; BEGIN open c1; update awesome_people set person_name = UPPER(person_name); close c1; END FOO_PROC; cursor my_cur is select * from awesome_people where person_name = 'John Doe' FOR UPDATE; BEGIN for onerow in c1 loop FOO_PROC(onerow.person_name); end loop; END;

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  • REST application, Transactions, Cache drop

    - by Julian Davchev
    Hi, I am building REST API in php with memcache layer on top for caching all resources. After some reading experience it turns out it's best when documents are as simple as posible...mainly due to dropping cache sequences. So if there is 'building','room' entities for the 'room' document I would only place the id of the 'building' and not the whole data of it. Then on api client side I would merge data as needed. Problem becomes when I need to update/insert (most cases more than one table). I update one resource but on second update system fails or whatever and there becomes database inconsistancies. I see several solutions: 1. Implement rest transactions which I find wrong and complex as idea is to be stateless and easy. 2. On update/insert actions I pass more complex data (not single entities) so I can force transactions on API level. But this will make it weird that your GET document structure is same as PUT document structure. And again somehow make drop sequences complex. Any pointers are more than welcome. Cheers,

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  • Better why of looping to detect change.

    - by Dremation
    As of now I'm using a while(true) method to detect changes in memory. The problem with this is it's kill the applications performance. I have a list of 30 pointers that need checked as rapidly as possible for changes, without sacrificing a huge performance loss. Anyone have ideas on this? memScan = new Thread(ScanMem); public static void ScanMem() { int i = addy.Length; while (true) { Thread.Sleep(30000); //I do this to cut down on cpu usage for (int j = 0; j < i; j++) { string[] values = addy[j].Split(new char[] { Convert.ToChar(",") }); //MessageBox.Show(values[2]); try { if (Memory.Scanner.getIntFromMem(hwnd, (IntPtr)Convert.ToInt32(values[0], 16), 32).ToString() != values[1].ToString()) { //Ok, it changed lets do our work //work if (Globals.Working) return; SomeFunction("Results: " + values[2].ToString(), "Memory"); Globals.Working = true; }//end if }//end try catch { } }//end for }//end while }//end void

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  • nasm/yasm arguments, linkage to C++

    - by arionik
    Hello everybody, I've got a question concerning nasm and its linkage to C++. I declare a litte test function as extern "C" void __cdecl myTest( byte i1, byte i2, int stride, int *width ); and I call it like this: byte i1 = 1, i2 = 2; int stride = 3, width = 4; myTest( i1, i2, stride, &width ); the method only serves to debug assembly and have a look at how the stack pointer is used to get the arguments. beyond that, the pointer arguments value shall be set to 7, to figure out how that works. This is implemented like this: global _myTest _myTest: mov eax, [esp+4] ; 1 mov ebx, [esp+8] ; 2 mov ecx, dword [esp+16] ; width mov edx, dword [esp+12] ; stride mov eax, dword [esp+16] mov dword [eax], 7 ret and compiled via yasm -f win32 -g cv8 -m x86 -o "$(IntDir)\$(InputName).obj" "$(InputPath)" , then linked to the c++ app. In debug mode, everything works fine. the function is called a couple of times and works as expected, whereas in release mode the function works once, but subsequent programm operations fail. It seems to me that something's wrong with stack/frame pointers, near/far, but I'm quite new to this subject and need a little help. thanks in advance! a.

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  • Linking session state between servlets and EJBs?

    - by wilth
    Hello, I have servlets (in a web module) that access stateless EJB beans (in an EJB module). The EJB module is built using SEAM. Users can have different roles and the EJB services check this using Seam's Identity. I also use a customized Authenticator (although this might not be relevant here). I noticed problems with this approach and I'm suspecting that the session context in the servlets is not "linked" with the session context in the EJB beans. What I think happens is something like: User Joe access servlet A and is assigned Session W1. Servlet A calls a login function on an EJB, using the EJB session E1. Later, user Mary accesses servlet A and is assigned Session W2. When calling the EJBs, however, the EJB session E1 is used and therefore Mary is authenticated as Joe. What also happens is that when Joe is calling the servlet twice in rapid succession, the same session W1 is used, but two different sessions E1 and E2 in the business layer, causing errors. I might be wrong in my suspicion, but maybe I'm actually expecting these "sessions" to be linked together while they in fact are not. If this is true, is there any way of achieving this? I could - of course - use stateful beans and save the authentication information in the beans, but this would break the "Identity" concept of Seam (and in general, it would be preferable to be able to use the Session context in my EJB beans). Any help and pointers are very welcome - thanks! Technology: EJB3, Seam 2.1.2. The servlets are actually the server-side of a GWT app, although I don't think this matters much. I'm using JBoss 5.

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  • ADO.NET Batch Insert with over 2000 parameters

    - by Liming
    Hello all, I'm using Enterprise library, but the idea is the same. I have a SqlStringCommand and the sql is constructed using StringBuilder in the forms of "insert into table (column1, column2, column3) values (@param1-X, @param2-X, @parm3-X)"+" " where "X" represents a "for loop" about 700 rows StringBuilder sb = new StringBuilder(); for(int i=0; i<700; i++) { sb.Append("insert into table (column1, column2, column3) values (@param1-"+i+", @param2-"+i, +",@parm3-"+i+") " ); } followed by constructing a command object injecting all the parameters w/ values into it. Essentially, 700 rows with 3 parameters, I ended up with 2100 parameters for this "one sql" Statement. It ran fine for about a few days and suddenly I got this error =============================================================== A severe error occurred on the current command. The results, if any, should be discarded. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.InternalExecuteNon Any pointers are greatly appreciated.

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  • Shopping list for developing Windows app on Mac

    - by raj.tiwari
    Folks, I need to maintain a C#/.Net desktop application. So, I need to set myself up with Windows(7?) and Visual Studio. My current development machine is a Macbook Pro and I would like to continue using it. Overall, I am considering the following recipe: Install VMWare Fusion or Parallels or VirtualBox for running the Windows OS Buy a version of Windows to develop on Buy Windows Developer tools Having been in the open source universe all this time, I am utterly unfamiliar with the options/packages in the Windows world. I could use some help on the following: Does the recipe above look fine, or do I need to change something? What is a good VM environment to buy/use? VirtualBox is free, but Parallels/VMWare promise Windows app that blend in with my Mac windows. Could use some help on this topic Does MSFT sell a package deal which has bare bones Windows 7 and the necessary dev tools, or do I need to buy the OS and dev tools separately? Since I only need Windows to churn this C# desktop application, What is the OS version and flavor or Visual Studio I should get? Thanks in advance for any pointers. -Raj

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  • Apache Axis: How to set call properties using code generated from wsdl2java?

    - by marc esher
    I'm using Apache Axis 1.4 (yes, the old one), with wsdl2java to generate the client code for a webservice. I'd like to set additional properties on the Call object before calling methods on the generated stub. For example, I'd like to set username, password, perhaps add or modify existing headers, and change the client handlers to use different implementations. Currently, I'm doing this by modifying the generated Stub class and calling the appropriate setters. However, I'd like to achieve this without touching the generated files. I"m confused, though, because the Stub class has: createCall() which creates the call object and sets some properties. Currently, this is where I'm modifying the generated source code; then, the Stub contains: clientMethod1(){ blahblah Call _call = createCall(); ...... _call.invoke(); } So I can't see a way that I can use the serviceLocator to get a stub, modify the properties I want to modify, and then use the stub to call the methods I want to call, given that the stub methods call createCall() and then call invoke. There doesn't appear to be a way to intercept the new Call object before it's invoked. So: How do you modify properties in the call without modifying the generated Stub class's source code? Thanks for info or even pointers to existing documentation.

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  • What are the primitive Forth operators?

    - by Barry Brown
    I'm interested in implementing a Forth system, just so I can get some experience building a simple VM and runtime. When starting in Forth, one typically learns about the stack and its operators (DROP, DUP, SWAP, etc.) first, so it's natural to think of these as being among the primitive operators. But they're not. Each of them can be broken down into operators that directly manipulate memory and the stack pointers. Later one learns about store (!) and fetch (@) which can be used to implement DUP, SWAP, and so forth (ha!). So what are the primitive operators? Which ones must be implemented directly in the runtime environment from which all others can be built? I'm not interested in high-performance; I want something that I (and others) can learn from. Operator optimization can come later. (Yes, I'm aware that I can start with a Turing machine and go from there. That's a bit extreme.) Edit: What I'm aiming for is akin to bootstrapping an operating system or a new compiler. What do I need do implement, at minimum, so that I can construct the rest of the system out of those primitive building blocks? I won't implement this on bare hardware; as an educational exercise, I'd write my own minimal VM.

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  • How can I connect to server using SSL(secure socket layer) on .NET Compact Framework

    - by net
    Hello. I want to change .NET framework v3.5 to .NET compact framework v3.5. But I can't change SSL Stream class to compact framework version. For resolving this problem, I already read some article and msdn library. http://blogs.msdn.com/cgarcia/archive/2009/08/21/enable-ssl-for-managed-socket-on-windows-mobile.aspx http://blogs.msdn.com/cgarcia/archive/2009/08/22/getting-a-managed-socket-to-talk-ssl.aspx http://msdn.microsoft.com/en-us/library/aa916117.aspx but I got an error that is "Unkown error 0x0ffffff", when invoking 'socket.connect(endPoint)' method based on thease article. In order to find the proper method, I try to use TcpClient class. but i can't solve this problem. When I try to connect to server on .NET compact framework, TcpClient class didn't work(Smart Device project and windows ce). As you can see below, I've got the error. In other hand, this code is work on .NET framework(C# console project). I can't understand why this socket can not access to server. Thanks for reading my question.

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  • PyGTK, Glade, Changing the window view and threads

    - by Gaunt Face
    Heya Everyone, Forgive me if this seems like a stupid question, just so far no where on the internet can I find someone offering a solution to this and I just wanted to get some feedback from someone with more experience than myself (I've only been using python, pyGTK and Glade for 2 days now). I have a UI window displaying and it updates with messages from a thread that is handling a bluetooth connection. This is fine and I have the application closing and running quite reliably, the problem is, after a bluetooth connection is made I wish to maintain the bluetooth thread (i.e. keep the connection going) but completely change the UI of the main window. Now the impression I am getting from pyGTK applications made from glade, is that the easiest thing to do is just open a new window. Is this really the best option? Can I cut the tree of widgets off at the root, maintaining the window widget but add on a new set of widgets from a separate glade file? If opening a new window is the best option, am I right in assuming that the bluetooth thread can be kept alive during this transition, providing I update any callbacks? Any help or pointers would be great. Cheers, Matt

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  • Is there a Standard or Best Practice for Perl Programs, as opposed to Perl Modules?

    - by swestrup
    I've written any number of perl modules in the past, and more than a few stand-alone perl programs, but I've never released a multi-file perl program into the wild before. I have a perl program that is almost at the beta stage and is going to be released open source. It requires a number of data files, as well as some external perl modules -- some I've written myself, and some from CPAN -- that I'll have to bundle with it so as to ensure that someone can just download my program and install it without worrying about hunting for obscure modules. So, it sounds to me like I need to write an installer to copy all the files to standard locations so that a user can easily install everything. The trouble is, I have no idea what the standard practice would be for this. I have found lots of tutorials on perl module standards, but none on perl program standards. Does anyone have any pointers to standard paths, installation proceedures, etc, for perl programs? This is going to be complicated by the fact that the program is multi-platform. I've been testing it in Linux, but its designed to work equally well in Windows.

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  • ajax-based login fails: IE6 and IE7 ajax calls delete session data (session_id however is kept)

    - by mateipavel
    This question comes after two days of testing and debugging, right after the shock I had seeing that none of the websites i build using ajax-based login work in IE<8 The most simplified scenario si this: 1. mypage.php : session_start(); $_SESSION['mytest'] = 'x'; <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"> </script> <script type="text/javascript"> function loadit() { $.post('http://www.mysite.com/myajax.php', {action: 'test'}, function(result){alert(result);}, 'html'); } </script> <a href="javascript:void(0);" onclick="loadit(); return false;">test link</a> 2. myajax.php session_start(); print_r($_SESSION); print session_id(); When I click the "test link", the ajax call is made and the result is alert()-ed: IE6: weird bullet-character (&bull;) IE7: Array( ) <session_id> IE8/FF (Expected behaviour): Array( [mytest] => 'x' ) <session_id> I would really appreciate some pointers regarding: 1. why this happens 2. how to fix it Thank you.

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  • Surprising results with .NET multi-theading algorithm

    - by Myles J
    Hi, I've recently wrote a C# console time tabling algorithm that is based on a combination of a genetic algorithm with a few brute force routines thrown in. The initial results were promising but I figured I could improve the performance by splitting the brute force routines up to run in parallel on multi processor architectures. To do this I used the well documented Producer/Consumer model (as documented in this fantastic article http://www.albahari.com/threading/part2.aspx#_ProducerConsumerQWaitHandle). I changed my code to create one thread per logical processor during the brute force routines. The performance gains on my work station were very pleasing. I am running Windows XP on the following hardware: Intel Core 2 Quad CPU 2.33 GHz 3.49 GB RAM Initial tests indicated average performance gains of approx 40% when using 4 threads. The next step was to deploy the new multi-threading version of the algorithm to our higher spec UAT server. Here is the spec of our UAT server: Windows 2003 Server R2 Enterprise x64 8 cpu (Quad-Core) AMD Opteron 2.70 GHz 255 GB RAM After running the first round of tests we were all extremely surprised to find that the algorithm actually runs slower on the high spec W2003 server than on my local XP work station! In fact the tests seem to indicate that it doesn't matter how many threads are generated (tests were ran with the app spawning between 2 to 32 threads). The algorithm always runs significantly slower on the UAT W2003 server? How could this be? Surely the app should run faster on a 8 cpu (Quad-Core) than my 2 Quad work station? Why are we seeing no performance gains with the multi-threading on the W2003 server whilst the XP workstation tests show gains of up to 40%? Any help or pointers would be appreciated. Regards Myles

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  • UIImage resize (Scale proportion)

    - by Mustafa
    The following piece of code is resizing the image perfectly, but the problem is that it messes up the aspect ratio (resulting in a skewed image). Any pointers? // Change image resolution (auto-resize to fit) + (UIImage *)scaleImage:(UIImage*)image toResolution:(int)resolution { CGImageRef imgRef = [image CGImage]; CGFloat width = CGImageGetWidth(imgRef); CGFloat height = CGImageGetHeight(imgRef); CGRect bounds = CGRectMake(0, 0, width, height); //if already at the minimum resolution, return the orginal image, otherwise scale if (width <= resolution && height <= resolution) { return image; } else { CGFloat ratio = width/height; if (ratio > 1) { bounds.size.width = resolution; bounds.size.height = bounds.size.width / ratio; } else { bounds.size.height = resolution; bounds.size.width = bounds.size.height * ratio; } } UIGraphicsBeginImageContext(bounds.size); [image drawInRect:CGRectMake(0.0, 0.0, bounds.size.width, bounds.size.height)]; UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return imageCopy; }

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  • Which Database to choose?

    - by Sundar
    I have the following criteria Database should be protected with a username and password. It should not be possible to copy the database file and use it else were like MS Access. There will be no central database server. Each machine will run their own database server locally and user will initiate synchronization. Concept is inspired from distributed version control system like Git. So it should have good replication support. Strong consistency is not needed. Users will synchronize each other database when they need. In case of conflicts it should be possible to find the conflict and present it (from application) to the user for fixing it. Revisions of data if available it will be good. e.g. Entire history of change to a invoice. I explored document oriented database and inclined towards the same. But I dont know what to choose. Database is small it will not reach even 1GB in the next few years (say 3 years). Please feel free to suggest any database which you think might be suitable. Any pointers is highly appreciated. Thanks in advance.

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  • Java design: too many getters

    - by dege
    After writing a few lesser programs when learning Java the way I've designed the programs is with Model-View-Control. With using MVC I have a plethora of getter methods in the model for the view to use. It feels that while I gain on using MVC, for every new value added I have to add two new methods in the model which quickly get all cluttered with getter & setters. So I was thinking, maybe I should use the notifyObserver method that takes an argument. But wouldn't feel very smart to send every value by itself either so I figured, maybe if I send a kind of container with all the values, preferably only those that actually changed. What this would accomplish would be that instead of having a whole lot of getter methods I could just have one method in the model which put all relevant values in the container. Then in the view I would have a method called from the update which extracted the values from the container and assigning them to the correct fields. I have two questions concerning this. First: is this actually a viable way to do this. Would you recommend me doing something along these lines? Secondly: if I do use this plan and I don't want to keep sending fields that didn't actually change. How would I handle that without having to have if statements to check if the value is not null for every single value?

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  • C++ .NET DLL vs C# Managed Code ? (File Encrypting AES-128+XTS)

    - by Ranhiru
    I need to create a Windows Mobile Application (WinMo 6.x - C#) which is used to encrypt/decrypt files. However it is my duty to write the encryption algorithm which is AES-128 along with XTS as the mode of operation. RijndaelManaged just doesn't cut it :( Very much slower than DES and 3DES CryptoServiceProviders :O I know it all depends on how good I am at writing the algorithm in the most efficient way. (And yes I my self have to write it from scratch but i can take a look @ other implementations) Nevertheless, does writing a C++ .NET DLL to create the encryption/decryption algorithm + all the file handling and using it from C# have a significant performance advantage OVER writing the encryption algorithm + file handling in completely managed C# code? If I use C++ .NET to create the encryption algorithm, should I use MFC Smart Device DLL or ATL? What is the difference and is there any impact on which one I choose? And can i just add a reference to the C++ DLL from C# or should I use P/Invoke? I am fairly competent with C# than C++ but performance plays a major role as I have convinced my lecturers that AES is a very efficient cryptographic algorithm for resource constrained devices. Thanx a bunch :)

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  • Figuring out the performance limitation of an ADC on a PIC microcontroller

    - by AKE
    I'm spec-ing the suitability of a microcontroller like PIC for an analog-to-digital application. This would be preferable to using external A/D chips. To do that, I've had to run through some computations, pulling the relevant parameters from the datasheets. I'm not sure I've got it right -- would appreciate a check! Here's the simplest example: PIC10F220 is the simplest possible PIC with an ADC. Runs at clock speed of 8MHz. Has an instruction cycle of 0.5us (4 clock steps per instruction) So: Taking Tacq = 6.06 us (acquisition time for ADC, assume chip temp. = 50*C) [datasheet p34] Taking Fosc = 8MHz (? clock speed) Taking divisor = 4 (4 clock steps per CPU instruction) This gives TAD = 0.5us (TAD = 1/(Fosc/divisor) ) Conversion time is 13*TAD [datasheet p31] This gives conversion time 6.5us ADC duration is then 12.56 us [? Tacq + 13*TAD] Assuming at least 2 instructions for load/store: This is another 1 us [0.5 us per instruction] Which would give max sampling rate of 73.7 ksps (1/13.56) Supposing 8 more instructions for real-time processing: This is another 4 us Thus, total ADC/handling time = 17.56us (12.56us + 1us + 4us) So expected upper sampling rate is 56.9 ksps. Nyquist frequency for this sampling rate is therefore 28 kHz. If this is right, it suggests the (theoretical) performance suitability of this chip's A/D is for signals that are bandlimited to 28 kHz. Is this a correct interpretation of the information given in the data sheet? Any pointers would be much appreciated! AKE

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  • UIView coordinate transforms on rotation during keyboard appearance

    - by SG
    iPad app; I'm trying to resize my view when the keyboard appears. It amounts to calling this code at appropriate times: CGRect adjustedFrame = self.frame; adjustedFrame.size.height -= keyboardFrame.size.height; [self setFrame:adjustedFrame]; Using this technique for a view contained in a uisplitview-based app works in all 4 orientations, but I've since discovered that a vanilla uiview-based app does not work. What happens is that apparently the uisplitview is smart enough to convert the coordinates of its subviews (their frame) such that the origin is in the "viewer's top left" regardless of the orientation. However, a uiview is not able to correctly report these coordinates. Though the origin is reported as (0,0) in all orientations, the view's effective origin is always as if the ipad were upright. What is weird about this is that the view correctly rotates and draws, but it always originates in the literal device top left. How can I get the view to correctly make its origin the "top left" to the viewer, not the device's fixed top left? What am I missing? Please, for something so trivial I've spent about 6 hours on this already with every brute force technique and research angle I could think of. This is the original source which doesn't work in this case: http://stackoverflow.com/questions/1951826/move-up-uitoolbar

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  • DDD and Client/Server apps

    - by Christophe Herreman
    I was wondering if any of you had successfully implemented DDD in a Client/Server app and would like to share some experiences. We are currently working on a smart client in Flex and a backend in Java. On the server we have a service layer exposed to the client that offers CRUD operations amongst some other service methods. I understand that in DDD these services should be repositories and services should be used to handle use cases that do not fit inside a repository. Right now, we mimic these services on the client behind an interface and inject implementations (Webservices, RMI, etc) via an IoC container. So some questions arise: should the server expose repositories to the client or do we need to have some sort of a facade (that is able to handle security for instance) should the client implement repositories (and DDD in general?) knowing that in the client, most of the logic is view related and real business logic lives on the server. All communication with the server happens asynchronously and we have a single threaded programming model on the client. how about mapping client to server objects and vice versa? We tried DTO's but reverted back to exposing the state of our objects and mapping directly to them. I know this is considered bad practice, but it saves us an incredible amount of time) In general I think a new generation of applications is coming with the growth of Flex, Silverlight, JavaFX and I'm curious how DDD fits into this.

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  • SQL (mySQL) update some value in all records processed by a select

    - by jdmuys
    I am using mySQL from their C API, but that shouldn't be relevant. My code must process records from a table that match some criteria, and then update the said records to flag them as processed. The lines in the table are modified/inserted/deleted by another process I don't control. I am afraid in the following, the UPDATE might flag some records erroneously since the set of records matching might have changed between step 1 and step 3. SELECT * FROM myTable WHERE <CONDITION>; # step 1 <iterate over the selected set of lines. This may take some time.> # step 2 UPDATE myTable SET processed=1 WHERE <CONDITION> # step 3 What's the smart way to ensure that the UPDATE updates all the lines processed, and only them? A transaction doesn't seem to fit the bill as it doesn't provide isolation of that sort: a recently modified record not in the originally selected set might still be targeted by the UPDATE statement. For the same reason, SELECT ... FOR UPDATE doesn't seem to help, though it sounds promising :-) The only way I can see is to use a temporary table to memorize the set of rows to be processed, doing something like: CREATE TEMPORARY TABLE workOrder (jobId INT(11)); INSERT INTO workOrder SELECT myID as jobId FROM myTable WHERE <CONDITION>; SELECT * FROM myTable WHERE myID IN (SELECT * FROM workOrder); <iterate over the selected set of lines. This may take some time.> UPDATE myTable SET processed=1 WHERE myID IN (SELECT * FROM workOrder); DROP TABLE workOrder; But this seems wasteful and not very efficient. Is there anything smarter? Many thanks from a SQL newbie.

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  • Clojure agents consuming from a queue

    - by erikcw
    I'm trying to figure out the best way to use agents to consume items from a Message Queue (Amazon SQS). Right now I have a function (process-queue-item) that grabs an items from the queue, and processes it. I want to process these items concurrently, but I can't wrap my head around how to control the agents. Basically I want to keep all of the agents busy as much as possible without pulling to many items from the Queue and developing a backlog (I'll have this running on a couple of machines, so items need to be left in the queue until they are really needed). Can anyone give me some pointers on improving my implementation? (def active-agents (ref 0)) (defn process-queue-item [_] (dosync (alter active-agents inc)) ;retrieve item from Message Queue (Amazon SQS) and process (dosync (alter active-agents dec))) (defn -main [] (def agents (for [x (range 20)] (agent x))) (loop [loop-count 0] (if (< @active-agents 20) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent)) ;should skip this agent until later if it is still busy processing (not sure how) (send-off agent process-queue-item))) ;(apply await-for (* 10 1000) agents) (Thread/sleep 10000) (logging/info (str "ACTIVE AGENTS " @active-agents)) (if (> 10 loop-count) (do (logging/info (str "done, let's cleanup " count)) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent))) (apply await agents) (shutdown-agents)) (recur (inc count)))))

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  • QT: I've inherited from QTreeView. I've inherited from QStandardItem. How do i Style the items?

    - by San Jacinto
    My Google skills must be failing me today. I've inherited from QTreeView to create a TreeView that stores a QStandardItemModel instead of a QAbstractItemModel. I have also inherited from QStandardItem to create a class to store my data in an item as is necessary. I've successfully inserted my derived QStandardItem into my derived QTreeView's QStandardItemModel. Now the trouble is, I can't figure out how to style it. I know that QTreeView has a setStyleSheet(QString) member, but I can't seem to get it working. It may be as simple as I'm not styling the correct attribute. Any pointers would be appreciated. Thanks. For clarity, here are my class defs. class SurveyTreeItem : public QStandardItem { public: SurveyTreeItem(); SurveyTreeItem( const QString & text ); ~SurveyTreeItem(); }; class StandardItemModelTreeView : public QTreeView { public: StandardItemModelTreeView(QWidget* parent = 0); ~StandardItemModelTreeView(); QStandardItemModel* getStandardItemModel(); }; I've tried the following StyleSheets: StandardTreeView::Item { font: 87 12pt 'Arial Black'; } StandardTreeView::QStandardItem { font: 87 12pt 'Arial Black'; } QTreeView::QStandardItem { font: 87 12pt 'Arial Black'; } QTreeView::Item { font: 87 12pt 'Arial Black'; } QTreeView::SurveyTreeItem { font: 87 12pt 'Arial Black'; } StandardTreeView::SurveyTreeItem { font: 87 12pt 'Arial Black'; }

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  • Django formsets: make first required?

    - by Mark
    These formsets are exhibiting exactly the opposite behavior that I want. My view is set up like this: def post(request): # TODO: handle vehicle formset VehicleFormSetFactory = formset_factory(VehicleForm, extra=1) if request.POST: vehicles_formset = VehicleFormSetFactory(request.POST) else: vehicles_formset = VehicleFormSetFactory() And my template looks like this: <div id="vehicle_forms"> {{ vehicles_formset.management_form }} {% for form in vehicles_formset.forms %} <h4>Vehicle {{forloop.counter}}</h4> <table> {% include "form.html" %} </table> {% endfor %} </div> That way it initially generates only 1 form, like I want. But I want that one form to be required! When I dynamically add blank forms with JavaScript and vehicles_formset.empty_form all those extra forms are required, which I don't want. From the docs: The formset is smart enough to ignore extra forms that were not changed. This is the behavior the first form is exhibiting (not what I want) but not the behavior that the extra forms are exhibiting (what I do want). Is there some attribute I can can change to at least make one form required?

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