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  • Understanding Java Wait and Notify methods

    - by Maddy
    Hello all: I have a following program: import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class SimpleWaitNotify implements Runnable { final static Object obj = new Object(); static boolean value = true; public synchronized void flag() { System.out.println("Before Wait"); try { obj.wait(); } catch (InterruptedException e) { System.out.println("Thread interrupted"); } System.out.println("After Being Notified"); } public synchronized void unflag() { System.out.println("Before Notify All"); obj.notifyAll(); System.out.println("After Notify All Method Call"); } public void run() { if (value) { flag(); } else { unflag(); } } public static void main(String[] args) throws InterruptedException { ExecutorService pool = Executors.newFixedThreadPool(4); SimpleWaitNotify sWait = new SimpleWaitNotify(); pool.execute(sWait); SimpleWaitNotify.value = false; SimpleWaitNotify sNotify = new SimpleWaitNotify(); pool.execute(sNotify); pool.shutdown(); } } When I wait on obj, I get the following exception Exception in thread "pool-1-thread-1" java.lang.IllegalMonitorStateException: current thread not owner for each of the two threads. But if I use SimpleWaitNotify's monitor then the program execution is suspended. In other words, I think it suspends current execution thread and in turn the executor. Any help towards understanding what's going on would be duly appreciated. This is an area1 where the theory and javadoc seem straightforward, and since there aren't many examples, conceptually left a big gap in me.

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  • pgf/tikz: String Symbols as Input Coordinates

    - by red_lynx
    Hi all, I'm new to pgf so i was trying out some examples from the pgfplot manual. One example is especially relevant for my current task but, alas, it would not compile. Here is the code: \documentclass[11pt]{article} \usepackage{tikz} \usepackage{pgfplots} \begin{document} \begin{tikzpicture} \begin{axis}[symbolic x coords={a,b,c,d,e,f,g,h,i}] \addplot+[smooth] coordinates { (a,42) (b,50) (c,80) (f,60) (g,62) (i,90)}; \end{axis} \end{tikzpicture} \end{document} the compiler quits with the following error: ! Package PGF Math Error: Could not parse input 'a' as a floating point number, sorry. The unreadable part was near 'a'.. I have no clue how to correct this behavior. Other plots (smooth, scatter, bar), which contain only numerical data compile fine. Could anybody give me a hint? Cheers K.

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  • Anyone know how to use TValue.AsType<TNotifyEvent> properly?

    - by Mason Wheeler
    I'm trying to use RTTI to add an event handler to a control, that may already have an event handler set. The code looks something like this: var prop: TRttiProperty; val: TValue; begin prop := FContext.GetType(MyControl.ClassInfo).GetProperty('OnChange'); val := prop.GetValue(MyControl); FOldOnChange := val.AsType<TNotifyEvent>; prop.SetValue(MyControl, TValue.From<TNotifyEvent>(self.MyOnChange)); end; I want this so I can do this in MyOnChange: begin if assigned(FOldOnChange) then FOldOnChange(Sender); //additional code here end; Unfortunately, the compiler doesn't seem to like the line FOldOnChange := val.AsType<TNotifyEvent>;. It says E2010 Incompatible types: 'procedure, untyped pointer or untyped parameter' and 'TNotifyEvent' Anyone know why that is or how to fix it? It looks right to me...

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  • Cmake suddenly can't find my source files anymore...

    - by aheld
    To make a long story short: To add insult to injury, CMake actually ran fine several times. I was wrestling with a compiler error when CMake suddenly didn't feel like working anymore. For reference, here's the whole CMakeLists.txt file: set(CMAKE_INCLUDE_CURRENT_DIR ON) Find_Package ( SDL REQUIRED ) Find_Package ( SDL_image REQUIRED ) Find_Package ( SDL_mixer REQUIRED ) if ( NOT SDL_FOUND ) message ( FATAL_ERROR "Make sure that SDL is installed" ) endif ( NOT SDL_FOUND ) link_libraries ( ${SDL_LIBRARY} ${SDLIMAGE_LIBRARY} ${SDLMIXER_LIBRARY} SDLmain ) set(wiggle_SOURCES level.cpp levelgenerator.cpp main.cpp player.cpp scoreboard.cpp snake.cpp soundplayer.cpp titlescreen.cpp ) add_executable(Wiggle ../${wiggle_SOURCES}) The error occured for the first time when, instead of simply typing "make", I typed "make -lSDL -lSDL_image -lSDL_mixer" - make refused to find the header files SDL.h and SDL_image.h after I detached the project from Code::Blocks.

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  • How to determine whether a class has a particular templated member function?

    - by Aozine
    I was wondering if it's possible to extend the SFINAE approach to detecting whether a class has a certain member function (as discussed here: "Is there a Technique in C++ to know if a class has a member function of a given signature?" http://stackoverflow.com/questions/87372/is-there-a-technique-in-c-to-know-if-a-class-has-a-member-function-of-a-given-s ) to support templated member functions? E.g. to be able to detect the function foo in the following class: struct some_class { template < int _n > void foo() { } }; I thought it might be possible to do this for a particular instantiation of foo, (e.g. check to see if void foo< 5 >() is a member) as follows: template < typename _class, int _n > class foo_int_checker { template < typename _t, void (_t::*)() > struct sfinae { }; template < typename _t > static big test( sfinae< _t, &_t::foo< _n > > * ); template < typename _t > static small test( ... ); public: enum { value = sizeof( test< _class >( 0 ) ) == sizeof( big ) }; }; Then do foo_int_checker< some_class, 5 >::value to check whether some_class has the member void foo< 5 >(). However on MSVC++ 2008 this always returns false while g++ gives the following syntax errors at the line test( sfinae< _t, &_t::foo< _n > > ); test.cpp:24: error: missing `>' to terminate the template argument list test.cpp:24: error: template argument 2 is invalid test.cpp:24: error: expected unqualified-id before '<' token test.cpp:24: error: expected `,' or `...' before '<' token test.cpp:24: error: ISO C++ forbids declaration of `parameter' with no type Both seem to fail because I'm trying to get the address of a template function instantiation from a type that is itself a template parameter. Does anyone know whether this is possible or if it's disallowed by the standard for some reason? EDIT: It seems that I missed out the ::template syntax to get g++ to compile the above code correctly. If I change the bit where I get the address of the function to &_t::template foo< _n > then the program compiles, but I get the same behaviour as MSVC++ (value is always set to false). If I comment out the ... overload of test to force the compiler to pick the other one, I get the following compiler error in g++: test.cpp: In instantiation of `foo_int_checker<A, 5>': test.cpp:40: instantiated from here test.cpp:32: error: invalid use of undefined type `class foo_int_checker<A, 5>' test.cpp:17: error: declaration of `class foo_int_checker<A, 5>' test.cpp:32: error: enumerator value for `value' not integer constant where line 32 is the enum { value = sizeof( test< _class >( 0 ) ) == sizeof( big ) }; line. Unfortunately this doesn't seem to help me diagnose the problem :(. MSVC++ gives a similar nondescript error: error C2770: invalid explicit template argument(s) for 'clarity::meta::big checker<_checked_type>::test(checker<_checked_type>::sfinae<_t,&_t::template foo<5>> *)' on the same line. What's strange is that if I get the address from a specific class and not a template parameter (i.e. rather than &_t::template foo< _n > I do &some_class::template foo< _n >) then I get the correct result, but then my checker class is limited to checking a single class (some_class) for the function. Also, if I do the following: template < typename _t, void (_t::*_f)() > void f0() { } template < typename _t > void f1() { f0< _t, &_t::template foo< 5 > >(); } and call f1< some_class >() then I DON'T get a compile error on &_t::template foo< 5 >. This suggests that the problem only arises when getting the address of a templated member function from a type that is itself a template parameter while in a SFINAE context. Argh!

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  • Adding Existing Framework to Xcode (iPhone) error

    - by Urizen
    I have added the <QuartzCore/QuartzCore.h> to my Frameworks folder in my iPhone project and added the #import "<QuartzCore/QuartzCore.h>" statement at the top of a custom UIView class. However the custom UIView class gives me a "No such file or directory" compliation error in relation to the <QuartzCore/QuartzCore.h> framework. Is there something else I need to set so that the compiler can see the framework. I'm not expert on the Xcode IDE so any assistance would be extremely welcome.

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  • "Socket operation on non-socket" error due to strange syntax

    - by Robert S. Barnes
    I ran across the error Socket operation on non-socket in some of my networking code when calling connect and spent a lot of time trying to figure out what was causing it. I finally figured out that the following line of code was causing the problem: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol) < 0)) { See the problem? Here's what the line should look like: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) { What I don't understand is why the first, incorrect line doesn't produce a warning. To put it another way, shouldn't the general form: if ( foo = bar() < baz ) do_something(); look odd to the compiler, especially running with g++ -Wall -Wextra? If not, shouldn't it at least show up as "bad style" to cppcheck, which I'm also running as part of my compile?

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  • In Delphi 7, why can I assign a value to a const?

    - by Blorgbeard
    I copied some Delphi code from one project to another, and found that it doesn't compile in the new project, though it did in the old one. The code looks something like this: procedure TForm1.CalculateGP(..) const Price : money = 0; begin ... Price := 1.0; ... end; So in the new project, Delphi complains that "left side cannot be assigned to" - understandable! But this code compiles in the old project. So my question is, why? Is there a compiler switch to allow consts to be reassigned? How does that even work? I thought consts were replaced by their values at compile time?

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  • Should I use concrete Inheritance or not?

    - by Mez
    I have a project using Propel where I have three objects (potentially more in the future) Occasion Event extends Occasion Gig extends Occasion Occasion is an item that has the shared things, that will always be needed (Venue, start, end etc) With this - I want to be able to add in extra functionality, say for example, adding "Band" objects to the Gig object, or "Flyers" to an "Event" object. For this, I plan to create objects for these. However, without concrete inheritance, I have to have the foreign key point to the Occasion object - giving the (propel generated) functions for all of these extra bits to anything inherited from Occasion. I could, in theory do this without a foreign constraint, and add in functions to use the Peer or Query classes to get things related to the "Gig" or similar. Whereas with concrete inheritance, I would only have these functions in the things where they are. I think the decision here is whether I should Duck Type the objects (after all they are occasions) or whether I should just use the "Occasion" object as a "template" (only being used to search for things, like, all occasions at a venue) Thoughts? Comments?

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  • Thread Proc for an instancable class?

    - by user146780
    Basically I have a class and it is instincable (not static). Basically I want the class to be able to generate its own threads and manage its own stuff. I don't want to make a global callback for each instance I make, this doesnt seem clean and proper to me. What is the proper way of doing what I want. If I try to pass the threadproc to CreateThread and it is the proc from a class instance the compiler says I cannot do this. What is the best way of achieving what I want? Thanks

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  • How to Install two library CGNS for Fortran under WIndows XP

    - by user317368
    Hello, I have to install two libraries CGNS to use it in Fortan, but I don't understand how, the basic instructions are: To compile under MS Windows: configure.bat [options] then gmake if using GNU make, or nmake if using nmake. NOTE: This assumes that the cl compiler is in your path, and that the INCLUDE and LIB environment variables are set to include the directories containing the MSC include files and libraries. If not, you will need to use full path names to cl and link, and define INCLUDE and LIB in make.win32. You may also execute VCVARS32.BAT in the BIN directory of your VC installation to set these up prior to running nmake. so what i did was to: tape configure.bat it creates the rights files I set the news paths and lib, include for the cl.exe and link.exe but now the warning and error messages are about the clui.dll. cl -nologo -I. -Iadf -FoWIN32\cgns_error.obj -c cgns_error.c Cannot load language resource clui.dll what can i do now? I'm a beginner user in this field. Thankx Manal

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  • Variable declarations following if statements

    - by Anthony Pegram
    An issue came up on another forum and I knew how to fix it, but it revealed a feature of the compiler peculiar to me. The person was getting the error "Embedded statement cannot be a declaration or labeled statement" because they had a declaration of a variable following an if statement with no brackets. That was not their intent, but they had commented out the line of code immediately following the if statement, which made the variable declaration the de facto line of code to execute. Anyway, that's the background, which brings me to this. The following code is illegal if (true) int i = 7; However, if you wrap that in brackets, it's all legal. if (true) { int i - 7; } Neither piece of code is useful. Yet the second one is OK. What specifically is the explanation for this behavior? I have a hypothesis, but I'd rather ask the brilliant people on stackoverflow.

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  • eclipse gcov plugin

    - by Taani
    I am using gcov plugin in Eclipse CDT + cygwin compiler & linker to find code coverage. I installed gcov plugin from http://svn.sourceforge.jp/svnroot/ginkgo/trunk/org.ginko.gcov.update/ location and follow the below link to get coverage of my .c file. I was able to create .gcno and .gcda files. But double clicking on those files, opens the files in eclipse editor. I could not find the gcov editor. Also I couldn't see any code coverage results in my .c file. What is the wrong with my procedure?

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  • gwt compiling error

    - by Hoax
    Compiling module com.sem.Sem10 Finding entry point classes [ERROR] Unable to find type 'com.sem.client.Sem10' [ERROR] Hint: Previous compiler errors may have made this type unavailable [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly My package structure is com.sem com.sem.client com.sem.schema com.sem.server inherits name='com.google.gwt.user.User' inherits name='com.google.gwt.user.theme.standard.Standard' inherits name='com.google.gwt.maps.GoogleMaps' script src="http://maps.google.com/maps?gwt=1&file=api&amp.... entry-point class='com.sem.client.Sem10' source path='com.sem.schema' I have googled this thing for quite a while and could not find a solution...? any help appreciated

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  • Decoding equivalent assembly code of C code...

    - by puffadder
    Hi All, Wanting to see the output of the compiler (in assembly) for some C code, I wrote a simple program in C and generated its assembly file using gcc. The code is this: #include <stdio.h> int main() { int i = 0; if ( i == 0 ) { printf("testing\n"); } return 0; } The generated assembly for it is here (only the main function): _main: pushl %ebpz movl %esp, %ebp subl $24, %esp andl $-16, %esp movl $0, %eax addl $15, %eax addl $15, %eax shrl $4, %eax sall $4, %eax movl %eax, -8(%ebp) movl -8(%ebp), %eax call __alloca call ___main movl $0, -4(%ebp) cmpl $0, -4(%ebp) jne L2 movl $LC0, (%esp) call _printf L2: movl $0, %eax leave ret I am at an absolute loss to correlate the C code and assembly code. All that the code has to do is store 0 in a register and compare it with a constant 0 and take suitable action. But what is going on in the assembly ? Thanks in advance.

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  • Setting generic type at runtime

    - by destroyer of evil
    I have a class public class A<T> { public static string B(T obj) { return TransformThisObjectToAString(obj); } } I can call the static function like this just fine on a known/specified type: string s= A<KnownType>.B(objectOfKnownType); How do I make this call, if I don't know T beforehand, rather I have a variable of type Type that holds the type. If I do this: Type t= typeof(string); string s= A<t>.B(someStringObject); I get this compiler error: Cannot implicitly convert type 't' to 'object'

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  • Is it normal for C++ static initialization to appear twice in the same backtrace?

    - by Joseph Garvin
    I'm trying to debug a C++ program compiled with GCC that freezes at startup. GCC mutex protects function's static local variables, and it appears that waiting to acquire such a lock is why it freezes. How this happens is rather confusing. First module A's static initialization occurs (there are __static_init functions GCC invokes that are visible in the backtrace), which calls a function Foo(), that has a static local variable. The static local variable is an object who's constructor calls through several layers of functions, then suddenly the backtrace has a few ??'s, and then it's is in the static initialization of a second module B (the __static functions occur all over again), which then calls Foo(), but since Foo() never returned the first time the mutex on the local static variable is still set, and it locks. How can one static init trigger another? My first theory was shared libraries -- that module A would be calling some function in module B that would cause module B to load, thus triggering B's static init, but that doesn't appear to be the case. Module A doesn't use module B at all. So I have a second (and horrifying) guess. Say that: Module A uses some templated function or a function in a templated class, e.g. foo<int>::bar() Module B also uses foo<int>::bar() Module A doesn't depend on module B at all At link time, the linker has two instances of foo<int>::bar(), but this is OK because template functions are marked as weak symbols... At runtime, module A calls foo<int>::bar, and the static init of module B is triggered, even though module B doesn't depend on module A! Why? Because the linker decided to go with module B's instance of foo::bar instead of module A's instance at link time. Is this particular scenario valid? Or should one module's static init never trigger static init in another module?

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  • gethostbyname fails for local hostname after resuming from hibernate (Vista+7?)

    - by John
    Just wondering if anyone else has spotted this: On some user's machines running our software, occasionally the call to Win32 winsock gethostbyname fails with error code 11004. For the argument to gethostbyname, I'm passing in the result from gethostname. Now the docs say 11004 is WSANO_DATA. None of the descriptions seem to be relevant (it occurs if you pass in an IP6 address, but as I say, I'm passing in a hostname). Even more interesting is that the MSDN suggests that this combination (gethostname followed by gethostbyname) should never fail, not even if there is no IP address (in that case it would just return empty list of IPs). Here is the quote from the gethostname MSDN entry: ...it is guaranteed that the name returned will be successfully parsed by gethostbyname and WSAAsyncGetHostByName. It only ever happens after resuming from hibernate, in that short period when the network is restarting, and only on Vista/7 (well I've only seen it on Vista and 7). One theory I had was that it related to IP6. Maybe for a short period the network reports an IP6 address but not the corresponging IP4 address (I'm pretty sure that all the client machines are dual IP stack, but I could be wrong). I tried to reproduce by turning off my network card (to force no IP addresses) and couldn't reproduce. Anyone seen this before? Any ideas? John

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  • Looping login with Facebook JS SDK and Rails

    - by nafe
    I'm using the Facebook JS SDK for single-sign with my rails app. I translated the php code from the Facebook example (at the bottom of the page under "Single Sign-on with the JavaScript SDK") into ruby. This appeared to be working great but I've noticed one user that gets continual redirects when trying to login. The logs look like: Processing UsersController#login (for X.X.X.X at 2010-05-22 17:25:55) [GET] Redirected to http://myapp.com/ Completed in 0ms (DB: 0) | 302 Found [http://myapp.com/login] (times as many entries as my unfortunate user leaves the browser redirecting in a loop). My client side code includes a callback with the "auth.sessionChange": FB.Event.subscribe('auth.sessionChange', function(response) { if (response.session) { // A user has logged in, and a new cookie has been saved window.location = "/login"; } else { // The user has logged out, and the cookie has been cleared window.location = "/logout"; } }); So it seems to me like this event is continually firing. Although, I can't test this theory because I can't recreate this scenario locally. I don't think it's the rails controller. The code here is just: def login # if first time user create db entry # now redirect back to where the user came from begin redirect_to :back rescue ActionController::RedirectBackError redirect_to root_url end end Does anyone have any idea on what's going on?

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  • Making Javascript and HTML5 games

    - by Jeff Meatball Yang
    A long time ago (Netscape 4-era), I wrote Javascript-based games: Pong, Minesweeper, and John Conway's Life among them. I'm getting back into it, and want to get my hands even dirtier. I have a few games in mind: Axis & Allies clone, with rugged maps and complex rules. Tetris clone, possibly with real-time player-vs-player or player-vs-computer mode Breakout clone, with a couple weapons and particle velocities In all of these, I have only a few objectives: Use JavaScript and HTML 5 - it should run on Chrome, Safari, or maybe an iPad. Start small and simple, then build-up features. Learn something new about game design and implementation. So my questions are: How would you implement these games? Do you have any technology recommendations? If you've written these games, what was the hardest part? N.B. I also want to start from first-principles - if you recommend a framework/library, I would appreciate some theory or implementation details behind it. These games are different enough that I should learn something new from each one.

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  • cmake and visual studio

    - by robUK
    Hello, gcc 4.4.2 / Visual Studio C++ 2008 I have been using cmake on linux, without any problems. Now I have ported by application to run on windows. I generated the solution files using cmake -G "Visual Studio 9 2008 ../src" However, I know that cmake only creates a Makefile that is used by the compiler to build your application. I open my solution in Visual Studio, I press the F7 key to compile. I am wondering does it actually use the Makefile that was generated by cmake? Or it is just compiling the application like any normal visual studio program? Many thanks for any advice,

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  • Expected specifier-qualifier-list before ... only in classes in a certain folder

    - by funkybro
    Hi Classes in my iPhone project are organised within folders on the filesystem, these correspond to groups (for each folder) in xcode. My problem is that there seems to be a particular class which classes in a particular group/folder cannot make reference to; the compiler complains of "Expected specifier-qualifier-list...". This happens on any class within this group, and also when I create a new class within this group and try and import the offending class like so: #import <Foundation/Foundation.h> #import "MyClass.h" @interface TryingToImport : NSObject { MyClass *myClass; // Expected specifier-qualifier-list before 'MyClass' } Creating an identical class in any other group works OK. I understand this error message is usually due to cyclical import references, I have checked over and over and there don't seem to be any of these. I assume I have inadvertantly configured the offending group to be different to the others in some way but I can't figure out how. Help please!

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  • Dependency Injection with @Inject in Weld (JSR-299 RI). How is the corresponding @Produces found?

    - by Thorbjørn Ravn Andersen
    I have played with the JSR-299 Reference Implementation "Weld" with the purpose of using it in a stand-alone application, and I have had a look at the documentation, and marveled at the magic. My question is how the producer of a given object to be @Inject'ed is found? Either the java compiler produces hints for annotations which is easily found by the classloader, or the complete classpath must be traversed loading all classes to see what they do which sounds highly inefficient to me, or it is a completely different approach. What is the trick?

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  • Removing a character from a string

    - by Prasanth Madhavan
    i have a string. I want to delete the last character of the string if it is a space. i tried the following code, str.erase(remove_if(str.begin(), str.end(), isspace), str.end()); but my g++ compiler gives me an error saying: error: no matching function for call to ‘remove_if(__gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, __gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, <unresolved overloaded function type>)’ please help.

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  • SQL Server database change workflow best practices

    - by kubi
    The Background My group has 4 SQL Server Databases: Production UAT Test Dev I work in the Dev environment. When the time comes to promote the objects I've been working on (tables, views, functions, stored procs) I make a request of my manager, who promotes to Test. After testing, she submits a request to an Admin who promotes to UAT. After successful user testing, the same Admin promotes to Production. The Problem The entire process is awkward for a few reasons. Each person must manually track their changes. If I update, add, remove any objects I need to track them so that my promotion request contains everything I've done. In theory, if I miss something testing or UAT should catch it, but this isn't certain and it's a waste of the tester's time, anyway. Lots of changes I make are iterative and done in a GUI, which means there's no record of what changes I made, only the end result (at least as far as I know). We're in the fairly early stages of building out a data mart, so the majority of the changes made, at least count-wise, are minor things: changing the data type for a column, altering the names of tables as we crystallize what they'll be used for, tweaking functions and stored procs, etc. The Question People have been doing this kind of work for decades, so I imagine there have got to be a much better way to manage the process. What I would love is if I could run a diff between two databases to see how the structure was different, use that diff to generate a change script, use that change script as my promotion request. Is this possible? If not, are there any other ways to organize this process? For the record, we're a 100% Microsoft shop, just now updating everything to SQL Server 2008, so any tools available in that package would be fair game.

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