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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • JavaScript regular expression literal persists between function calls

    - by Charles Anderson
    I have this piece of code: function func1(text) { var pattern = /([\s\S]*?)(\<\?(?:attrib |if |else-if |else|end-if|search |for |end-for)[\s\S]*?\?\>)/g; var result; while (result = pattern.exec(text)) { if (some condition) { throw new Error('failed'); } ... } } This works, unless the throw statement is executed. In that case, the next time I call the function, the exec() call starts where it left off, even though I am supplying it with a new value of 'text'. I can fix it by writing var pattern = new RegExp('.....'); instead, but I don't understand why the first version is failing. How is the regular expression persisting between function calls? (This is happening in the latest versions of Firefox and Chrome.) Edit Complete test case: <!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-type" content="text/html;charset=UTF-8"> <title>Test Page</title> <style type='text/css'> body { font-family: sans-serif; } #log p { margin: 0; padding: 0; } </style> <script type='text/javascript'> function func1(text, count) { var pattern = /(one|two|three|four|five|six|seven|eight)/g; log("func1"); var result; while (result = pattern.exec(text)) { log("result[0] = " + result[0] + ", pattern.index = " + pattern.index); if (--count <= 0) { throw "Error"; } } } function go() { try { func1("one two three four five six seven eight", 3); } catch (e) { } try { func1("one two three four five six seven eight", 2); } catch (e) { } try { func1("one two three four five six seven eight", 99); } catch (e) { } try { func1("one two three four five six seven eight", 2); } catch (e) { } } function log(msg) { var log = document.getElementById('log'); var p = document.createElement('p'); p.innerHTML = msg; log.appendChild(p); } </script> </head> <body><div> <input type='button' id='btnGo' value='Go' onclick='go();'> <hr> <div id='log'></div> </div></body> </html> The regular expression continues with 'four' as of the second call on FF and Chrome, not on IE7 or Opera.

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  • How do I make a sql query where fields are the result of a different query?

    - by CRP
    I have two tables, the first is like this: f1 | f2 | f3 | f4 ----------------- data.... the second contains info about the fields of the first: field | info ------------ f1 a f2 b f3 a etc. I would like to query the first table selecting the fields with a query on the second. So, for example, I might want to get data for fields where info is equal to "a", thus I would do "select f1, f3 from first_table". How do I do this programmatically? I was thinking about something along the lines of select (select fields from second_table where info='a') from first_table Thanks Chris

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  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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  • Manhattan Heuristic function for A-star (A*)

    - by Shawn Mclean
    I found this algorithm here. I have a problem, I cant seem to understand how to set up and pass my heuristic function. static public Path<TNode> AStar<TNode>(TNode start, TNode destination, Func<TNode, TNode, double> distance, Func<TNode, double> estimate) where TNode : IHasNeighbours<TNode> { var closed = new HashSet<TNode>(); var queue = new PriorityQueue<double, Path<TNode>>(); queue.Enqueue(0, new Path<TNode>(start)); while (!queue.IsEmpty) { var path = queue.Dequeue(); if (closed.Contains(path.LastStep)) continue; if (path.LastStep.Equals(destination)) return path; closed.Add(path.LastStep); foreach (TNode n in path.LastStep.Neighbours) { double d = distance(path.LastStep, n); var newPath = path.AddStep(n, d); queue.Enqueue(newPath.TotalCost + estimate(n), newPath); } } return null; } As you can see, it accepts 2 functions, a distance and a estimate function. Using the Manhattan Heuristic Distance function, I need to take 2 parameters. Do I need to modify his source and change it to accepting 2 parameters of TNode so I can pass a Manhattan estimate to it? This means the 4th param will look like this: Func<TNode, TNode, double> estimate) where TNode : IHasNeighbours<TNode> and change the estimate function to: queue.Enqueue(newPath.TotalCost + estimate(n, path.LastStep), newPath); My Manhattan function is: private float manhattanHeuristic(Vector3 newNode, Vector3 end) { return (Math.Abs(newNode.X - end.X) + Math.Abs(newNode.Y - end.Y)); }

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  • jquery event handler- trigger function upon specific key and action

    - by Gal
    Background story: when a user selects a portion of text in a text field with her mouse (mark it up manually), and subsequently hits "alt" key, a certain function would trigger. My questions are: How can I trigger a function when a user hits a key (in her keyboard)? How can I preserve a portion of text selected, and use it as a parameter for that function? I've tried looking up online but haven't found any good answers, but i'd greatly appreciate links as well.

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  • List of functions references

    - by Ockonal
    Hello, I'm using boost::function for making references to the functions. Can I make a list of references? For example: boost::function<bool (Entity &handle)> behaviorRef; And I need in a list of such pointers. For example: std::vector<behaviorRef> listPointers; Of course it's wrong code due to behaviorRef isn't a type. So the question is: how can I store a list of pointers for the function?

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  • routine to generate a 2d array from two 1d arrays and a function

    - by intuited
    I'm guessing that there's a word for this concept, and that it's available in at least some popular languages, but my perfunctory search was fruitless. A pseudocode example of what I'd like to do: function foo(a, b) { return a * b // EG } a = [ 1, 2, 3 ] b = [ 4, 5, 6 ] matrix = the_function_for_which_I_search(foo, [a, b] ) print matrix => [ [ 4, 8, 12], [5, 10, 15], [6, 12, 18] ] // or function concatenate(a,b) return a.b } print the_function_for_which_I_search( concatenate, [ a, b ]) => [ [ '14', '24', '34'], ['15', '25', '35'], [16', '26', '36'] ] In other words, function_for_which_I_search will apply the function given as its first argument to each combination of the elements of the two arrays passed as its second argument, and return the results as a two-dimensional array. I would like to know if such a routine has a common name, and if it's available in a python module, cpan package, ruby gem, pear package, etc. I'm also wondering if this is a core function in other languages, maybe haskell or R?

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  • Get ID of clicked on element in function

    - by skerit
    I want to get the ID of an element I click on. I put the function in the onclick element, like this: <a id="myid" class="first active" onclick="markActiveLink();" href="#home">Home</a> And this is in the function: function markActiveLink() { alert($(this).attr("id")); } This doesn't work, as it says it isn't defined. Does it really forget about the ID, do I have to type it in the onclick?

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  • How to call user define function when excel sheet being opened

    - by Nimo
    Hi, I'm trying to call a function when a workbook is being opened. I used workbook_open() event. But I notice that before calling function which is inside workbook_open(), all the functions that already exists in the workbook are being called. How can I call my function to execute before calling any of functions in the workbook? Thank you

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  • Help me reduce code repetition in a simple jQuery function

    - by user339876
    I have built a carousel using the jQuery cycle plugin. I have 4 links that jump to relevent slides. Right now I have a chunk of code for each link. I am trying to create a single multi-purpose function. $('#features-slide0').click(function() { $('#features-slides').cycle(0); return false; }); $('#features-slide1').click(function() { $('#features-slides').cycle(1); return false; }); $('#features-slide2').click(function() { $('#features-slides').cycle(2); return false; }); $('#features-slide3').click(function() { $('#features-slides').cycle(3); return false; }); I have a rel value on each link that carries the number of the slide. How can I use that to create a single block of code that takes care of the link jump?

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  • How do I trace SQL Server Failure Audit events?

    - by Tim Perry
    I recently took over management of a Windows 2003 server. The application log is being filled up with messages like these: Event Type: Failure Audit Event Source: MSSQLSERVER Event Category: (4) Event ID: 18456 Date: 3/5/2010 Time: 4:00:30 PM User: N/A Computer: FAIROAKS1 Description: Login failed for user 'administrator'. [CLIENT: <local machine>] Data: 0000: 18 48 00 00 0e 00 00 00 .H...... 0008: 0a 00 00 00 46 00 41 00 ....F.A. 0010: 49 00 52 00 4f 00 41 00 I.R.O.A. 0018: 4b 00 53 00 31 00 00 00 K.S.1... 0020: 07 00 00 00 6d 00 61 00 ....m.a. 0028: 73 00 74 00 65 00 72 00 s.t.e.r. 0030: 00 00 .. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. I'd like to figure out what program is causing these. Is there a way to trace and find out which process is causing these errors?

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  • JNI: dll function works ok in C++ main, but not with dll wrapper

    - by Joseph Lim
    I have an a.dll (not modifiable as i do not have the source) with a function bool openPort(DWORD mem).I wrote a c++ main, loaded this dll using LoadLibrary, and the function works well.It returns true. Now, I need to call this function from Java via JNI. I wrote another b.dll with a function like so JNIEXPORT void JNICALL Java_MyClass_openPortFunc (JNIEnv *env, jobject obj, jint pMemPhy) { hInstLibrary = LoadLibrary("a.dll"); typedef bool (*openPort)(DWORD); openPort _openPort; _openPort = (openPort)GetProcAddress(hInstLibrary, "openPort"); DWORD memAddr = 0xda000; if(_openPort(memAddr)){ cout << "ok" << endl; }else{ cout << "failed " << endl; } } This however, causes the openPort to return false despite using the same parameters. I hope someone can advise me. Thank you. :)

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  • OpenOffice Calc Macro: Run shell command and return output as result of custom function

    - by Mark
    I would like to write a custom OpenOffice function that runs a shell command and puts the result into the cell from which it was invoked. I have a basic macro working, but I can't find a way to capture the command's output. Function MyTest( c1 ) MyTest = Shell("bash -c "" echo hello "" ") End Function The above always returns 0. Looking at the documentation of the Shell command, I don't think it actually returns STDOUT. How would I capture the output so that I can return it in my function? Thanks!

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  • QList as a function parameter - Linking Error - LNK2019

    - by user2445136
    I have an issue with QList as a function parameter and I'll be glad if you can assist me. I have this code for example: void SpinBoxList_Enable(QList spinBoxList) { foreach(QWidget mWidget,*spinBoxList) mWidget-setEnabled(false); } and in the implemantation file I use the QList variable as a pointer: SpinBoxList_Enable(&controlBoardSpinBoxList); ( controlBoardSpinBoxList is a variable of QList ). The Function ToggleBoards_Slot(bool) is a slot that uses When I compile, I get this error message: 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Disable(class QList *)" (?SpinBoxList_Disable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "public: void __cdecl CMosaixSerialNumber::ToggleBoards_Slot(bool)" (?ToggleBoards_Slot@CMosaixSerialNumber@@QEAAX_N@Z) 1cmosaixserialnumber.obj : error LNK2019: unresolved external symbol "private: void __cdecl CMosaixSerialNumber::SpinBoxList_Enable(class QList *)" (?SpinBoxList_Enable@CMosaixSerialNumber@@AEAAXPEAV?$QList@PEAVQWidget@@@@@Z) referenced in function "private: void __cdecl CMosaixSerialNumber::on_ControlBoardCheckBox_StateChanged(int)" (?on_ControlBoardCheckBox_StateChanged@CMosaixSerialNumber@@AEAAXH@Z) How can I fix this ? Thanks, EVH671

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  • Cannot add an entity that already exists. (LINQ to SQL)

    - by Vicheanak
    Hello guys, in my database there are 3 tables CustomerType CusID EventType EventTypeID CustomerEventType CusID EventTypeID Dim db = new CustomerEventDataContext Dim newEvent = new EventType newEvent.EventTypeID = txtEventID.text db.EventType.InsertOnSubmit(newEvent) db.SubmitChanges() 'To select the last ID of event' Dim lastEventID = (from e in db.EventType Select e.EventTypeID Order By EventTypeID Descending).first() Dim chkbx As CheckBoxList = CType(form1.FindControl("CheckBoxList1"), CheckBoxList) Dim newCustomerEventType = New CustomerEventType Dim i As Integer For i = 0 To chkbx.Items.Count - 1 Step i + 1 If (chkbx.Items(i).Selected) Then newCustomerEventType.INTEVENTTYPEID = lastEventID newCustomerEventType.INTSTUDENTTYPEID = chkbxStudentType.Items(i).Value db.CustomerEventType.InsertOnSubmit(newCustomerEventType) db.SubmitChanges() End If Next It works fine when I checked only 1 Single ID of CustomerEventType from CheckBoxList1. It inserts data into EventType with ID 1 and CustomerEventType ID 1. However, when I checked both of them, the error message said Cannot add an entity that already exists. Any suggestions please? Thx in advance.

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  • Getting ellipses function parameters without an initial argument

    - by Tox1k
    So I've been making a custom parser for a scripting language, and I wanted to be able to pass only ellipses arguments. I don't need or want an initial variable, however Microsoft and C seem to want something else. FYI, see bottom for info. I've looked at the va_* definitions #define _crt_va_start(ap,v) ( ap = (va_list)_ADDRESSOF(v) + _INTSIZEOF(v) ) #define _crt_va_arg(ap,t) ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) ) #define _crt_va_end(ap) ( ap = (va_list)0 ) and the part I don't want is the v in va_start. As a little background I'm competent in goasm and I know how the stack works so I know what's happening here. I was wondering if there is a way to get the function stack base without having to use inline assembly. Ideas I've had: #define im_va_start(ap) (__asm { mov [ap], ebp }) and etc... but really I feel like that's messy and I'm doing it wrong. struct function_table { const char* fname; (void)(*fptr)(...); unsigned char maxArgs; }; function_table mytable[] = { { "MessageBox", &tMessageBoxA, 4 } }; ... some function that sorts through a const char* passed to it to find the matching function in mytable and calls tMessageBoxA with the params. Also, the maxArgs argument is just so I can check that a valid number of parameters is being sent. I have personal reasons for not wanting to send it in the function, but in the meantime we can just say it's because I'm curious. This is just an example; custom libraries are what I would be implementing so it wouldn't just be calling WinAPI stuff. void tMessageBoxA(...) { // stuff to load args passed MessageBoxA(arg1, arg2, arg3, arg4); } I'm using the __cdecl calling convention and I've looked up ways to reliably get a pointer to the base of the stack (not the top) but I can't seem to find any. Also, I'm not worried about function security or typechecking.

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  • How do I rescue a small portion of data from a SQL Server database backup?

    - by Greg
    I have a live database that had some data deleted from it and I need that data back. I have a very recent copy of that database that has already been restored on another machine. Unrelated changes have been made to the live database since the backup, so I do not want to wipe out the live database with a full restore. The data I need is small - just a dozen rows - but those dozen rows each have a couple rows from other tables with foreign keys to it, and those couple rows have god knows how many rows with foreign keys pointing to them, so it would be complicated to restore by hand. Ideally I'd be able to tell the backup copy of the database to select the dozen rows I need, and the transitive closure of everything that they depend on, and everything that depends on them, and export just that data, which I can then import into the live database without touching anything else. What's the best approach to take here? Thanks. Everyone has mentioned sp_generate_inserts. When using this, how do you prevent Identity columns from messing everything up? Do you just turn IDENTITY INSERT on?

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  • No getdate() function in Enterprise PostgreSQL

    - by Suezy
    Hi guys, do you have any idea on how to have getdate() function in enterprise postgresql? I upgraded to EDB-PSQL, and now when I tried to restore old data from the free PSQL, it returns error on some tables since there is no getdate(). I believe this should automatically be created upon creating new database? But it didn't. :( Only now() function. Can I create the function instead? Help!

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  • Preprocessor "macro function" vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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