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• Large scale Merge Replication strategy - what can go wrong?

  - by niidto

  Hi, I'm developing a piece of software that uses Merge Replication and SQL Compact on Windows Mobile 6. At the moment it is running on 5 devices reasonably well. The issues I've come up against are as follows: The schema has had to change a lot, and will continue to have to change as the application evolves. There have been various errors replicating these schema changes down to the device, uploads failing due to schema inconsistencies. Subscriptions expiring (after 14 days) and unable to reinitialize with upload - AKA, potential data los of unsynced data up to that point. Basically, the worst case scenario is data loss, and when merge replication fails, there seems to be no way back to get the data off. My method until now has been to drop and create the subscription on the device. I don't hear many people doing this, though it seems to solve everything. The long term plan is to role this out to 500+ devices. Any advice on people who have undertaken similar projects, and how to minimise data loss and make it so that there's appropriate error handling code to recover from sync failures would be much appreciated. James

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• iPhone inputting NSUserDefaults into a UITextField

  - by Rob

  I am writing a program where I where the first time a user runs it - they will have to fill out about 10 different UITextFields. I am trying to save the fields so that on subsequent runs of the program that whatever they previously put will already be displayed in those UITextFields so the wont have to re-input it in - unless they want to edit something in which case they still have that option. I think that I have figured out a good way to save the strings using NSUserDefaults but now I am trying to figure out how to have those fields populate a UITextField - it doesnt seem as easy as if they were UILabels. This is the route I am attempting: // in the viewDidLoad portion. NSUserDefaults *userData = [NSUserDefaults standardUserDefaults]; //Hooks. NSString *placeHolderName = [userData stringForKey:@"name"]; txtName.text = @"%@", placeHolderName; When I do this, it simply displays the '%@' in the textfields. I want whatever variable being held by placeHolderName to be automatically put into that UITextField. Is this possible?

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• Hibernate Transient Extends problem

  - by mrvreddy

  @MappedSuperclass public abstract class BaseAbstract implements Serializable{ private static final long serialVersionUID = 1L; protected String test = //some random value; public String getTest() { return test; } public void setTest(String test){ this.test = test; } } @Entity public class Artist extends BaseAbstract { private static final long serialVersionUID = 1L; private Integer id; @override @Transient public String getTest() { return test; } ..... } My question is... when i am trying to do any operation on the artist, along with id and name, test is also getting saved which should not be the case... if i add the same transient on the baseabstract class getTest() method, i see test column NOT getting created(ideally what it should happen) but if i try to override the method with adding annotaion in the sub class it creates the test column... I dont know why this is happening since when hibernate is creating the artist object and checks for annotations, it should see the transient annotation present on the getTest() of artist method...and should not create a column in the database... Let me know if you need any clarification.... Any response on this is greatly appreciated.... Thank you

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• Data Warehouse: Modelling a future schedule

  - by Pat

  I'm creating a DW that will contain data on financial securities such as bonds and loans. These securities are associated with payment schedules. For example, a bond could pay quarterly, while a mortage would usually pay monthly (sometimes biweekly). The payment schedule is created when the security is traded and, in the majority of cases, will remain unchanged. However, the design would need to accomodate those cases where it does change. I'm currently attempting to model this data and I'm having difficulty coming up with a workable design. One of the most commonly queried fields is "next payment date". Users often want to know when a security will pay next. Therefore, I want to make it as easy as possible for them to get the next payment date and amount for each security. Also, users often run historical queries in which case they'd want the next payment date and amount as of a specific point in time. For example, they may want to look back at 1/31/09 and query the next payment dates (which would usually be in February 2009 for mortgages). It's also common that they want to query a security's entire payment schedule, which might consist of 360 records (30 year mortgage x 12 payments/year). Since the next payment date and amount would be changing each month or even biweekly, these fields wouldn't seem to fit into a slow-changing dimension very well. It would probably make more sense to use a fact table, but I'm unsure of how to model it. Any ideas would be greatly appreciated.

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• Returning JSON object from an ASP.NET page

  - by Emin

  Hi, In my particular situation, I have couple of solutions to my problem. I want to find out which one is more feasible. In this case, I can also achieve my goal by returning a JSON object from my server side code, however, I do not know how it is done and what is the best way of doing it. First off, I don't need a full aspx page as I only need a response returned from code. So, do I use web services? handler? or is there any other specific way you people do this? Is this solution feasible? do I build the JSON string using the StringBuilder class and inject that string into the target aspx page? are there any precautions? or things that I should be aware of? I appreciate your ideas. Regards, Kemal ------------UPDATE !------------ Suppose I have a JSON object in my userlist.aspx page. which then I use it with jQuery... {"menu": { "id": "color1", "value": "color", "popup": { "menuitem": [ {"value": "Red"}, {"value": "Green"}, {"value": "Yellow"} ] } }} // example taken from the json.org/example page now when I want to add a new menuitem from my aspx page, what do I do... I think this way my question is more specific... Lets assume I create a new string in my aspx code, as such "{"value": "Blue"}. Now how do I inject this into the already existing itemlist in the target page? or is this not the correct approach to this kind of situation? if not how else can it be achieved? Also if I wanted to fire a jquery event when a new item is added to this list, how is this achieved?

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• Most watched videos this week

  - by Jan Hancic

  I have a youtube like web-page where users upload&watch videos. I would like to add a "most watched videos this week" list of videos to my page. But this list should not contain just the videos that ware uploaded in the previous week, but all videos. I'm currently recording views in a column, so I have no information on when a video was watched. So now I'm searching for a solution to how to record this data. The first is the most obvious (and the correct one, as far as I know): have a separate table in which you insert a new line every time you want to record a new view (storing the ID of the video and the timestamp). I'm worried that I would quickly get huge amounts of data in this table, and queries using this table would be extremely slow (we get about 3 million views a month). The second solution isn't as flexible but is more easy on the database. I would add 7 columns to the "videos" table (one for each day of the week): views_monday, views_tuesday , views_wednesday, ... And increment the value in the correct column based on the day it is. And I would reset the current day's column to 0 at midnight. I could then easily get the most watched videos of the week by summing this 7 columns. What do you think, should I bother with the first solution or will the second one suffice for my case? If you have a better solution please share! Oh, I'm using MySQL.

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• Four-color theorem in Prolog (using a dynamic predicate)

  - by outa

  Hi, I'm working on coloring a map according to the four-color theorem (http://en.wikipedia.org/wiki/Four_color_theorem) with SWI-Prolog. So far my program looks like this: colour(red). colour(blue). map_color(A,B,C) :- colour(A), colour(B), colour(C), C \= B, C \= A. (the actual progam would be more complex, with 4 colors and more fields, but I thought I'd start out with a simple case) Now, I want to avoid double solutions that have the same structure. E.g. for a map with three fields, the solution "red, red, blue" would have the same structure as "blue, blue, red", just with different color names, and I don't want both of them displayed. So I thought I would have a dynamic predicate solution/3, and call assert(solution(A,B,C)) at the end of my map_color predicate. And then, for each solution, check if they already exist as a solution/3 fact. The problem is that I would have to assert something like solution(Color1,Color1,Color2), i.e. with variables in order to make a unification check. And I can't think of a way to achieve this. So, the question is, what is the best way to assert a found solution and then make a unification test so that "red, red, blue" would unify with "blue, blue, red"?

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• Powershell: splatting after passing hashtable by reference

  - by user1815871

  Powershell newbie ... I recently learned about splatting — very useful. I ran into a snag when I passed a hash table by reference to a function for splatting purposes. (For brevity's sake — a silly example.) Function AllMyChildren { param ( [ref]$ReferenceToHash } get-childitem @ReferenceToHash.Value # etc.etc. } $MyHash = @{ 'path' = '*' 'include' = '*.ps1' 'name' = $null } AllMyChildren ([ref]$MyHash) Result: an error ("Splatted variables cannot be used as part of a property or array expression. Assign the result of the expression to a temporary variable then splat the temporary variable instead."). Tried this afterward: $newVariable = $ReferenceToHash.Value get-childitem @NewVariable That did work and seemed right per the error message. But: is it the preferred syntax in a case like this? (An oh, look, it actually worked solution isn't always a best practice. My approach here strikes me as "Perl-minded" and perhaps in Powershell passing by value is better, though I don't yet know the syntax for it w.r.t. a hash table.)

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• How to do an additional search on archive in rails if record not found, by extending model?

  - by Nick Gorbikoff

  Hello, I was wondering if somebody knows an elegant solution to the following: Suppose I have a table that holds orders, with a bunch of data. So I'm at 1M records, and searches begin to take time. So I want to speed it up by archiving some data that is more than 3 years old - saving it into a table called orders-archive, and then purging them from the orders table. So if we need to research something or customer wants to pull older information - they still can, but 99% of the lookups are done on the orders no older than a year and a half - so there is no reason to keep looking through older data all the time. These move & purge operations can be then croned to be done on a weekly basis. I already did some tests and I know that I will slash my search times by about 4 times. So far so good, right? However I was thinking about how to implement older archival lookups and the only reasonable thing I can think of is some sort of if-else If not found in orders, do a search in orders-archive. However - I have about 20 tables that I want to archive and god knows how many searches / finds are done through out the code, that I don't want to modify. So I was wondering if there is an elegant rails-way solution to this problem, by extending a model somehow? Has anyone dealt with similar case before? Thank you.

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• Using Java classes(whole module with Spring/Hibernate dependency) in Grails

  - by Sitaram

  I have a Java/Spring/Hibernate application with a payment module. Payment module has some domain classes for payment subscription and transactions etc. Corresponding hibernate mapping files are there. This module uses applicationContext.xml for some of the configuration it needs. Also, This module has a PaymentService which uses a paymentDAO to do all database related work. Now, I want to use this module as it is(without any or minimal re-writing) in my other application(Grails application). I want to bring in the payment module as a jar or copy the source files to src/java folder in Grails. With that background, I have following queries: Will the existing applicationContext.xml for Spring configuration in the module will work as it is in Grails? Does it merge with rest of Grails's Spring config? Where do I put the applicationContext.xml? classpath? src/java should work? Can I bundle the applicationContext.xml in Jar(If I use jar option) and can overwrite in Grails if anything needs to be changed? Multiple bean definition problems in that case? PaymentService recognized as regular service? Will it be auto-injected in controllers and/or other services? Will PaymentDAO use the datasource configuration of Grails? Where do I put the hbm files of this module? Can I bundle the hbm files in Jar(If I use jar option) and can overwrite in Grails if anything needs to be changed? Which hbms are picked? or, there will be problems with that? Too many questions! :) All these concerns are actually before trying. I am going to try this in next few days(busy currently). Any help is appreciated. Thanks. Sitaram Meena

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• waveInProc / Windows audio question...

  - by BTR

  I'm using the Windows API to get audio input. I've followed all the steps on MSDN and managed to record audio to a WAV file. No problem. I'm using multiple buffers and all that. I'd like to do more with the buffers than simply write to a file, so now I've got a callback set up. It works great and I'm getting the data, but I'm not sure what to do with it once I have it. Here's my callback... everything here works: // Media API callback void CALLBACK AudioRecorder::waveInProc(HWAVEIN hWaveIn, UINT uMsg, DWORD dwInstance, DWORD dwParam1, DWORD dwParam2) { // Data received if (uMsg == WIM_DATA) { // Get wav header LPWAVEHDR mBuffer = (WAVEHDR *)dwParam1; // Now what? for (unsigned i = 0; i != mBuffer->dwBytesRecorded; ++i) { // I can see the char, how do get them into my file and audio buffers? cout << mBuffer->lpData[i] << "\n"; } // Re-use buffer mResultHnd = waveInAddBuffer(hWaveIn, mBuffer, sizeof(mInputBuffer[0])); // mInputBuffer is a const WAVEHDR * } } // waveInOpen cannot use an instance method as its callback, // so we create a static method which calls the instance version void CALLBACK AudioRecorder::staticWaveInProc(HWAVEIN hWaveIn, UINT uMsg, DWORD_PTR dwInstance, DWORD_PTR dwParam1, DWORD_PTR dwParam2) { // Call instance version of method reinterpret_cast<AudioRecorder *>(dwParam1)->waveInProc(hWaveIn, uMsg, dwInstance, dwParam1, dwParam2); } Like I said, it works great, but I'm trying to do the following: Convert the data to short and copy into an array Convert the data to float and copy into an array Copy the data to a larger char array which I'll write into a WAV Relay the data to an arbitrary output device I've worked with FMOD a lot and I'm familiar with interleaving and all that. But FMOD dishes everything out as floats. In this case, I'm going the other way. I guess I'm basically just looking for resources on how to go from LPSTR to short, float, and unsigned char. Thanks much in advance!

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• Threads are blocked in malloc and free, virtual size

  - by Albert Wang

  Hi, I'm running a 64-bit multi-threaded program on the windows server 2003 server (X64), It run into a case that some of the threads seem to be blocked in the malloc or free function forever. The stack trace is like follows: ntdll.dll!NtWaitForSingleObject() + 0xa bytes ntdll.dll!RtlpWaitOnCriticalSection() - 0x1aa bytes ntdll.dll!RtlEnterCriticalSection() + 0xb040 bytes ntdll.dll!RtlpDebugPageHeapAllocate() + 0x2f6 bytes ntdll.dll!RtlDebugAllocateHeap() + 0x40 bytes ntdll.dll!RtlAllocateHeapSlowly() + 0x5e898 bytes ntdll.dll!RtlAllocateHeap() - 0x1711a bytes MyProg.exe!malloc(unsigned __int64 size=0) Line 168 C MyProg.exe!operator new(unsigned __int64 size=1) Line 59 + 0x5 bytes C++ ntdll.dll!NtWaitForSingleObject() ntdll.dll!RtlpWaitOnCriticalSection() ntdll.dll!RtlEnterCriticalSection() ntdll.dll!RtlpDebugPageHeapFree() ntdll.dll!RtlDebugFreeHeap() ntdll.dll!RtlFreeHeapSlowly() ntdll.dll!RtlFreeHeap() MyProg.exe!free(void * pBlock=0x000000007e8e4fe0) C BTW, the param values passed to the new operator is not correct here maybe due to optimization. Also, at the same time, I found in the process Explorer, the virtual size of this program is 10GB, but the private bytes and working set is very small (<2GB). We did have some threads using virtualalloc but in a way that commit the memory in the call, and these threads are not blocked. m_pBuf = VirtualAlloc(NULL, m_size, MEM_COMMIT, PAGE_READWRITE); ...... VirtualFree(m_pBuf, 0, MEM_RELEASE); This looks strange to me, seems a lot of virtual space is reserved but not committed, and malloc/free is blocked by lock. I'm guessing if there's any corruptions in the memory/object, so plan to turn on gflag with pageheap to troubleshoot this. Does anyone has similar experience on this before? Could you share with me so I may get more hints? Thanks a lot!

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• `enable_shared_from_this` has a non-virtual destructor

  - by Shtééf

  I have a pet project with which I experiment with new features of the upcoming C++0x standard. While I have experience with C, I'm fairly new to C++. To train myself into best practices, (besides reading a lot), I have enabled some strict compiler parameters (using GCC 4.4.1): -std=c++0x -Werror -Wall -Winline -Weffc++ -pedantic-errors This has worked fine for me. Until now, I have been able to resolve all obstacles. However, I have a need for enable_shared_from_this, and this is causing me problems. I get the following warning (error, in my case) when compiling my code (probably triggered by -Weffc++): base class ‘class std::enable_shared_from_this<Package>’ has a non-virtual destructor So basically, I'm a bit bugged by this implementation of enable_shared_from_this, because: A destructor of a class that is intended for subclassing should always be virtual, IMHO. The destructor is empty, why have it at all? I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this. But I'm looking for ways to deal with this, so my question is really, is there a proper way to deal with this? And: am I correct in thinking that this destructor is bogus, or is there a real purpose to it?

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• How do I check to see if a scalar has a compiled regex in it with Perl?

  - by Robert P

  Let's say I have a subroutine/method that a user can call to test some data that (as an example) might look like this: sub test_output { my ($self, $test) = @_; my $output = $self->long_process_to_get_data(); if ($output =~ /\Q$test/) { $self->assert_something(); } else { $self->do_something_else(); } } Normally, $test is a string, which we're looking for anywhere in the output. This was an interface put together to make calling it very easy. However, we've found that sometimes, a straight string is problematic - for example, a large, possibly varying number of spaces...a pattern, if you will. Thus, I'd like to let them pass in a regex as an option. I could just do: $output =~ $test if I could assume that it's always a regex, but ah, but the backwards compatibility! If they pass in a string, it still needs to test it like a raw string. So in that case, I'll need to test to see if $test is a regex. Is there any good facility for detecting whether or not a scalar has a compiled regex in it?

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• Get active window title in X

  - by dutt

  I'm trying to get the title of the active window. The application is a background task so if the user has Eclipse open the function returns "Eclipse - blabla", so it's not getting the window title of my own window. I'm developing this in Python 2.6 using PyQt4. My current solution, borrowed and slightly modified from an old answer here at SO, looks like this: def get_active_window_title(): title = '' root_check = '' root = Popen(['xprop', '-root'], stdout=PIPE) if root.stdout != root_check: root_check = root.stdout for i in root.stdout: if '_NET_ACTIVE_WINDOW(WINDOW):' in i: id_ = i.split()[4] id_w = Popen(['xprop', '-id', id_], stdout=PIPE) for j in id_w.stdout: if 'WM_ICON_NAME(STRING)' in j: if title != j.split()[2]: return j.split("= ")[1].strip(' \n\"') It works for most windows, but not all. For example it can't find my kopete chat windows, or the name of the application i'm currently developing. My next try looks like this: def get_active_window_title(self): screen = wnck.screen_get_default() if screen == None: return "Could not get screen" window = screen.get_active_window() if window == None: return "Could not get window" title = window.get_name() return title; But for some reason window is always None. Does somebody have a better way of getting the current window title, or how to modify one of my ways, that works for all windows? Edit: In case anybody is wondering this is the way I found that seems to work for all windows. def get_active_window_title(self): root_check = '' root = Popen(['xprop', '-root'], stdout=PIPE) if root.stdout != root_check: root_check = root.stdout for i in root.stdout: if '_NET_ACTIVE_WINDOW(WINDOW):' in i: id_ = i.split()[4] id_w = Popen(['xprop', '-id', id_], stdout=PIPE) id_w.wait() buff = [] for j in id_w.stdout: buff.append(j) for line in buff: match = re.match("WM_NAME\((?P<type>.+)\) = (?P<name>.+)", line) if match != None: type = match.group("type") if type == "STRING" or type == "COMPOUND_TEXT": return match.group("name") return "Active window not found"

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• Why does my DIV clip its child DIV when jQuery moves it in IE?

  - by Ben Saufley

  I have two divs, both with position:absolute;, one inside the other. The parent isn't in a place where it can be set as position:relative without an extra layer of complexity (there are a lot of other elements around it that I'd have to account for to put it where it needs to be, which is at the very top of the page, over everything). The child element is made to stick off the bottom of the parent. In Chrome, Safari, Firefox, it all works splendidly. In IE, it works until jQuery moves the parent element - at which point the parent element clips the child, so you can barely see the top of the child. I feel like I've read about this, about IE clipping child elements, but I can't seem to find an answer that applies to my case. It's pretty simple, basically: <div id="parent" style="position:absolute;top:0;left:0;"> [content] <div id="tab" style="position:absolute;bottom:-30px;left:0;width:64px;height:32px;background-image:(...);"></div> </div> <script> $(document).ready( function() { $("#tab").click(function() { $("#parent").animate({"top":"-50px"},300); }); }); </script>

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• NUnit - Multiple properties of the same name? Linking to requirements

  - by Ryan Ternier

  I'm linking all our our System Tests to test cases and to our Requirements. Every requirement has an ID. Every Test Case / System Tests tests a variety of requirements. Every module of code links to multiple requirements. I'm trying to find the best way to link every system test to its driving requirements. I was hoping to do something like: [NUnit.Framework.Property("Release", "6.0.0")] [NUnit.Framework.Property("Requirement", "FR50082")] [NUnit.Framework.Property("Requirement", "FR50084")] [NUnit.Framework.Property("Requirement", "FR50085")] [TestCase(....)] public void TestSomething(string a, string b...) However, that will break because Property is a Key-Value pair. The system will not allow me to have multiple Properties with the same key. The reason I'm wanting this is to be able to test specific requirements in our system if a module changes that touches these requirements. Rather than run over 1,000 system tests on every build, this would allow us to target what to test based on changes done to our code. Some system tests run upwards of 5 minutes (Enterprise healthcare system), so "Just run all of them" isn't a viable solution. We do that, but only before promoting through our environments. Thoughts?

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• I expect to see in the browswer "http://path/some_page.html" but instead it identifies with "http:/

  - by indiehacker

  I am developing with app engine SDK. I have a feeling this is much too basic a question so apologies ahead of time... A simple submit button doesnt work instead of just showing an alert box as expected it continues on afterwards and redirects me to the latest http-request, and I think this is because I dont understand how to tell the browser to recognize the proper URLs. Why does my browser say I am at the most recent http-request http://localhost:8080/putProjectInDB rather than the somepage.html that was actually served to the browser that I am currently looking at? How can I get the browser to recognize and show in its url spot the normal expected http://somepage.html ? Just in case, here are details of the specific problem which you might be able to ignore for answering the question: This hasnt been mattered for me until I just wanted to put into my .html a simple button that changes some stuff of the page without needing the server. The below code after displaying the alert box redirects me to the last server request http://localhost:8080/putProjectInDB instead of just staying in the same html page. in header: function MyFormCommands() { alert('Some Text'); } in body: <form onSubmit="MyFormCommands()" ><input type=submit ></form >

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• Move SELECT to SQL Server side

  - by noober

  Hello all, I have an SQLCLR trigger. It contains a large and messy SELECT inside, with parts like: (CASE WHEN EXISTS(SELECT * FROM INSERTED I WHERE I.ID = R.ID) THEN '1' ELSE '0' END) AS IsUpdated -- Is selected row just added? as well as JOINs etc. I like to have the result as a single table with all included. Question 1. Can I move this SELECT to SQL Server side? If yes, how to do this? Saying "move", I mean to create a stored procedure or something else that can be executed before reading dataset in while cycle. The 2 following questions make sense only if answer is "yes". Why do I want to move SELECT? First off, I don't like mixing SQL with C# code. At second, I suppose that server-side queries run faster, since the server have more chances to cache them. Question 2. Am I right? Is it some sort of optimizing? Also, the SELECT contains constant strings, but they are localizable. For instance, WHERE R.Status = "Enabled" "Enabled" should be changed for French, German etc. So, I want to write 2 static methods -- OnCreate and OnDestroy -- then mark them as stored procedures. When registering/unregistering my assembly on server side, just call them respectively. In OnCreate format the SELECT string, replacing {0}, {1}... with required values from the assembly resources. Then I can localize resources only, not every script. Question 3. Is it good idea? Is there an existing attribute to mark methods to be executed by SQL Server automatically after (un)registartion an assembly? Regards,

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• How to handle window closed in the middle of a long running operation gracefully?

  - by Marek

  We have the following method called directly from the UI thread: void DoLengthyProcessing() { DoStuff(); var items = DoMoreStuff(); //do even more stuff - 200 lines of code trimmed this.someControl.PrepareForBigThing(); //someControl is a big user control //additional 100 lines of code that access this.someControl this.someControl.Finish(items); } Many of the called methods call Application.DoEvents() (and they do so many times) (do not ask me why, this is black magic written by black magic programmers and it can not be changed because everyone is scared what the impact would be) and there is also an operation running on a background thread involved in the processing. As a result, the window is not fully nonresponsive and can be closed manually during the processing. The Dispose method of the form "releases" the someControl variable by setting it to null. As a result, in case the user closes the window during the lengthy process, a null reference exception is thrown. How to handle this gracefully without just catching and logging the exception caused by disposal? Assigning the someControl instance to a temporary variable in the beginning of the method - but the control contains many subcontrols with similar disposal scheme - sets them to null and this causes null reference exceptions in other place put if (this.IsDisposed) return; calls before every access of the someControl variable. - making the already nasty long method even longer and unreadable. in Closing event, just indicate that we should close and only hide the window. Dispose it at the end of the lengthy operation. This is not very viable because there are many other methods involved (think 20K LOC for a single control) that would need to handle this mechanism as well. How to most effectively handle window disposal (by user action) in the middle of this kind of processing?

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• Stop NSXMLParser Instance from Causing _NSAutoreleaseNoPool

  - by PF1

  Hi Everyone: In my iPhone application, I have an instance of NSXMLParser that is set to a custom delegate to read the XML. This is then moved into its own thread so it can update the data in the background. However, ever since I have done this, it has been giving me a lot of _NSAutoreleaseNoPool warnings in the console. I have tried to add a NSAutoreleasePool to each of my delegate classes, however, this hasn't seemed to solve the problem. I have included my method of creating the NSXMLParser in case that is at fault. NSURL *url = [[NSURL alloc] initWithString:@"http://www.mywebsite.com/xmlsource.xml"]; NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:url]; CustomXMLParser *parser = [[CustomXMLParser alloc] init]; parser.managedObjectContext = self.managedObjectContext; parser = [parser initXMLParser]; [xmlParser setDelegate:parser]; [NSThread detachNewThreadSelector:@selector(parse) toTarget:xmlParser withObject:nil]; If anyone has any ideas to get rid of this problem, I would really appreciate it. Thanks.

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• Performance of a get unique elements/group by operation on an IEnumerable<T>.

  - by tolism7

  I was wondering how could I improve the performance of the following code: public class MyObject { public int Year { get; set; } } //In my case I have 30000 IEnumerable<MyObject> data = MethodThatReturnsManyMyObjects(); var groupedByYear = data.GroupBy(x => x.Year); //Here is the where it takes around 5 seconds foreach (var group in groupedByYear) //do something here. The idea is to get a set of objects with unique year values. In my scenario there are only 6 years included in the 30000 items in the list so the foreach loop will be executed 6 times only. So we have many items needing to be grouped in a few groups. Using the .Distinct() with an explicit IEqualityComparer would be an alternative but somehow I feel that it wont make any difference. I can understand if 30000 items is too much and that i should be happy with the 5 seconds I get, but I was wondering if the above can be imporved performance wise. Thanks.

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• Standard term for a thread I/O reorder buffer?

  - by Crashworks

  I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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• How long is the time frame between context switches on Windows?

  - by mattcodes

  Reading CLR via C# 2.0 (I dont have 3.0 with me at the moment) Is this still the case: If there is only one CPU in a computer, only one thread can run at any one time. Windows has to keep track of the thread objects, and every so often, Windows has to decide which thread to schedule next to go to the CPU. This is additional code that has to execute once every 20 milliseconds or so. When Windows makes a CPU stop executing one thread's code and start executing another thread's code, we call this a context switch. A context switch is fairly expensive because the operating system has to: So circa CLR via C# 2.0 lets say we are on Pentium 4 2.4ghz 1 core non-HT, XP. Every 20 milliseconds? Where a CLR thread or Java thread is mapped to an OS thread only a maximum of 50 threads per second may get a chance to to run? I've read that context switching is very fast in mircoseconds here on SO, but how often roughly (magnitude style guesses) will say a modest 5 year old server Windows 2003 Pentium Xeon single core give the OS the opportunity to context switch? 20ms in the right area? I dont need exact figures I just want to be sure that's in the right area, seems rather long to me.

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