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  • Why is it bad to use boolean flags in databases? And what should be used instead?

    - by David Chanin
    I've been reading through some of guides on database optimization and best practices and a lot of them suggest not using boolean flags at all in the DB schema (ex http://forge.mysql.com/wiki/Top10SQLPerformanceTips). However, they never provide any reason as to why this is bad. Is it a peformance issue? is it hard to index or query properly? Furthermore, if boolean flags are bad, what should you use to store boolean values in a database? Is it better to store boolean flags as an integer and use a bitmask? This seems like it would be less readable.

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  • How can I sort an NSTableColumn of NSStrings ignoring "The " and "A "?

    - by David Barry
    I've got a simple Core Data application that I'm working on to display my movie collection. I'm using an NSTableView, with it's columns bound to attributes of my Core Data store through an NSArrayController object. At this point the columns sort fine(for numeric values) when the column headers are clicked on. The issue I'm having is with the String sorting, they sort, however it's done in standard string fashion, with Uppercase letters preceding lowercase(i.e. Z before a). In addition to getting the case sorting to work properly, I would like to be able to ignore a prefix of "The " or "A " when sorting the strings. What is the best way to go about this in Objective-C/Cocoa?

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  • Is the Unix Philosophy still relevant in the Web 2.0 world?

    - by David Titarenco
    Introduction Hello, let me give you some background before I begin. I started programming when I was 5 or 6 on my dad's PSION II (some primitive BASIC-like language), then I learned more and more, eventually inching my way up to C, C++, Java, PHP, JS, etc. I think I'm a pretty decent coder. I think most people would agree. I'm not a complete social recluse, but I do stuff like write a virtual machine for fun. I've never taken a computer course in college because I've been in and out for the past couple of years and have only been taking core classes; never having been particularly amazing at school, perhaps I'm missing some basic tenet that most learn in CS101. I'm currently reading Coders at Work and this question is based on some ideas I read in there. A Brief (Fictionalized) Example So a certain sunny day I get an idea. I hire a designer and hammer away at some C/C++ code for a couple of months, soon thereafter releasing silvr.com, a website that transmutes lead into silver. Yep, I started my very own start-up and even gave it a clever web 2.0 name with a vowel missing. Mom and dad are proud. I come up with some numbers I should be seeing after 1, 2, 3, 6, 9, 12 months and set sail. Obviously, my transmuting server isn't perfect, sometimes it segfaults, sometimes it leaks memory. I fix it and keep truckin'. After all, gdb is my best friend. Eventually, I'm at a position where a very small community of people are happily transmuting lead into silver on a semi-regular basis, but they want to let their friends on MySpace know how many grams of lead they transmuted today. And they want to post images of their lead and silver nuggets on flickr. I'm losing out on potential traffic unless I let them log in with their Yahoo, Google, and Facebook accounts. They want webcam support and live cock fighting, merry-go-rounds and Jabberwockies. All these things seem necessary. The Aftermath Of course, I have to re-write the transmuting server! After all, I've been losing money all these months. I need OAuth libraries and OpenID libraries, JSON support, and the only stable Jabberwocky API is for Java. C++ isn't even an option anymore. I'm just one guy! The Java binary just grows and grows since I need some legacy Apache include for the JSON library, and some antiquated Sun dependency for OAuth support. Then I pick up a book like Coders at Work and read what people like jwz say about complexity... I think to myself.. Keep it simple, stupid. I like simple things. I've always loved the Unix Philosophy but even after trying to keep the new server source modular and sleek, I loathe having to write one more line of code. It feels that I'm just piling crap on top of other crap. Maybe I'm naive thinking every piece of software can be simple and clever. Maybe it's just a phase.. or is the Unix Philosophy basically dead when it comes to the current state of (web) development? I'm just kind of disheartened :(

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  • A matter of style

    - by David
    Would you write something like: enum XYZ_TYPE {X=1, Y=2, Z=3}; I saw it and the suffix _TYPE confuses me in the enum context. There is a strong prospect that it is because I am not bright.

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  • How can I equalize the heights of text input fields?

    - by David
    What is the best way to equalize the height of my <select..> elements and my <input type="text"..> elements? It's proving difficult because of differences in box-sizing models. Google Chrome's user agent stylesheet has this: select { -webkit-box-sizing: border-box; } ..whereas other text input fields use the content box model. Why the difference? Should I perhaps make all of my text-based input fields use the border-box model? BTW, I'm using standards-compliant mode (by using <!DOCTYPE html>).

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  • Uploading multiple files simultaneously with Flex

    - by David
    I have been working on a flex uploader, where the user can select multiple files. It works fine when the files are uploaded in a queue (one at a time), however as soon as I try to have it upload 2 files at once I run into issues. It seems that files will often lock up, and either stay at 1% until every other file is uploaded, or just not complete at all. There is never more than one file uploading at a time. Is there some issue with calling .upload on multiple files at once in Flex?

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  • Best way to handle global state

    - by David
    Hi there, I was wondering if anyone could offer some advice on 'best practices' for using global state in a web application - specifically PHP, although im looking for generic best practices i.e. design patterns etc. At the moment I just use a static class, calling it Configs. I suppose this is similar to using the registry pattern but surely there is a more elegant way of handling global data within an application - i just cant think of a better way though.

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  • Is it valid to use unsafe struct * as an opaque type instead of IntPtr in .NET Platform Invoke?

    - by David Jeske
    .NET Platform Invoke advocates declaring pointer types as IntPtr. For example, the following [DllImport("user32.dll")] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); However, I find when interfacing with interesting native interfaces, that have many pointer types, flattening everything into IntPtr makes the code very hard to read and removes the typical typechecking that a compiler can do. I've been using a pattern where I declare an unsafe struct to be an opaque pointer type. I can store this pointer type in a managed object, and the compiler can typecheck it form me. For example: class Foo { unsafe struct FOO {}; // opaque type unsafe FOO *my_foo; class if { [DllImport("mydll")] extern static unsafe FOO* get_foo(); [DllImport("mydll")] extern static unsafe void do_something_foo(FOO *foo); } public unsafe Foo() { this.my_foo = if.get_foo(); } public unsafe do_something_foo() { if.do_something_foo(this.my_foo); } While this example may not seem different than using IntPtr, when there are several pointer types moving between managed and native code, using these opaque pointer types for typechecking is a godsend. I have not run into any trouble using this technique in practice. However, I also have not seen an examples of anyone using this technique, and I wonder why. Is there any reason that the above code is invalid in the eyes of the .NET runtime? My main question is about how the .NET GC system treats "unsafe FOO *my_foo". Is this pointer something the GC system is going to try to trace, or is it simply going to ignore it? My hope is that because the underlying type is a struct, and it's declared unsafe, that the GC would ignore it. However, I don't know for sure. Thoughts?

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  • Running Stored Procedure with parameters resulting from query

    - by David in Dakota
    It's not hard to find developers who think cursors are gauche but I am wondering how to solve the following problem without one: Let's say I have a proc called uspStudentDelete that takes as a parameter @StudentID. uspStudentDelete applies a bunch of cascading soft delete logic, marking a flag on tables like "classes", "grades", and so on as inactive. uspStudentDelete is well vetted and has worked for some time. What would be the best way to run uspStudentDelete on the results of a query (e.g. select studentid from students where ... ) in *TSQL*?

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  • Create a user-defined aggregate without SQL CLR

    - by David Pfeffer
    I am planning on deploying a database to SQL Azure, so I cannot use the SQL CLR. However, I have a need to create an aggregate function -- in my case, I need to STUnion a bunch of Geography objects together. (Azure is expected to support Spatial by June.) Is there another way to accomplish this, without making use of the CLR, in a query? Or do I have to create a UDF that will take a table as a parameter and return the aggregate?

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  • May volatile be in user defined types to help writing thread-safe code

    - by David Rodríguez - dribeas
    I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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  • How do I override generic activerecord error messages in ruby-on-rails?

    - by David Smith
    In my en.yml translation file, I have: activerecord: errors: template: header: one: "1 error prohibited this {{model}} from being saved" other: "{{count}} errors prohibited this {{model}} from being saved" When an activerecord/validation error occurs during logging into my application, the error message: "1 error prohibited this user session from being saved" is displayed (where user_session is the model being used). I'd rather have it say something like "An error has occured to prevent you from logging into your account". How do I override the generic error message with my specific one?

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  • "Priming" a whole database in MSSQL for first-hit speed

    - by David Spillett
    For a particular apps I have a set of queries that I run each time the database has been restarted for any reason (server reboot usually). These "prime" SQL Server's page cache with the common core working set of the data so that the app is not unusually slow the first time a user logs in afterwards. One instance of the app is running on an over-specced arrangement where the SQL box has more RAM than the size of the database (4Gb in the machine, the DB is under 1.5Gb currently and unlikely to grow too much relative to that in the near future). Is there a neat/easy way of telling SQL Server to go away and load everything into RAM? It could be done the hard way by having a script scan sysobjects & sysindexes and running SELECT * FROM <table> WITH(INDEX(<index_name>)) ORDER BY <index_fields> for every key and index found, which should cause every used page to be read at least once and so be in RAM, but is there a cleaner or more efficient way? All planned instances where the database server is stopped are out-of-normal-working-hours (all the users are at most one timezone away and unlike me none of them work at silly hours) so such a process (until complete) slowing down users more than the working set not being primed at all would is not an issue.

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  • Equivalent of http://www.cplusplus.com/ for C# .net

    - by David Relihan
    Hi Folks I've read through a lot of the "Learn C# .Net" questions just to see if this question was answered already (directly or indirectly). I program mostly in C++ so I find the website http://www.cplusplus.com/ invaluable and there's rarely a day when it is not open in my browser! However, I'm just wondering is there an C# .Net equivalent that people find themselves constantly referencing? The best I'm aware of is: http://stackoverflow.com http://msdn.microsoft.com/en-us/vcsharp/aa336809.aspx http://www.java2s.com/Tutorial/CSharp/CatalogCSharp.htm Thanks,

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  • Which is the best .NET image capture API for me to use?

    - by David
    I have been tasked with integrating image acquisition into a .NET application and I have been looking for an API to use for performing this function. I have come across several "standard" APIs, some have been in existence for a long time, some not so long. I have looked at references to ISIS, TWAIN, WIA, and SANE (said to be mostly *nix). They all appear to be Win32 libraries except for SANE, and I was wondering what the current recommendations are for talking to image acquisition devices (scanners)? Feel free to recommend something else if you feel it is better. I'm looking for open source options. Edit: I put open source, when what I actually meant was free. using WIA or TWAIN is fine since they are free even though they are proprietary interfaces.

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  • What's the Matlab equivalent of NULL, when it's calling COM/ActiveX methods?

    - by David M
    Hi, I maintain a program which can be automated via COM. Generally customers use VBS to do their scripting, but we have a couple of customers who use Matlab's ActiveX support and are having trouble calling COM object methods with a NULL parameter. They've asked how they do this in Matlab - and I've been scouring Mathworks' COM/ActiveX documentation for a day or so now and can't figure it out. Their example code might look something like this: function do_something() OurAppInstance = actxserver('Foo.Application'); OurAppInstance.Method('Hello', NULL) end where NULL is where in another language, we'd write NULL or nil or Nothing, or, of course, pass in an object. The problem is this is optional (and these are implemented as optional parameters in most, but not all, cases) - these methods expect to get NULL quite often. They tell me they've tried [] (which from my reading seemed the most likely) as well as '', Nothing, 'Nothing', None, Null, and 0. I have no idea how many of those are even valid Matlab keywords - certainly none work in this case. Can anyone help? What's Matlab's syntax for a null pointer / object for use as a COM method parameter? Update: Thanks for all the replies so far! Unfortunately, none of the answers seem to work, not even libpointer. The error is the same in all cases: Error: Type mismatch, argument 2 This parameter in the COM type library is described in RIDL as: HRESULT _stdcall OurMethod([in] BSTR strParamOne, [in, optional] OurCoClass* oParamTwo, [out, retval] VARIANT_BOOL* bResult); The coclass in question implements a single interface descending from IDispatch.

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  • Returning recursive ternary freaks out

    - by David Titarenco
    Hi, assume this following function: int binaryTree::findHeight(node *n) { if (n == NULL) { return 0; } else { return 1 + max(findHeight(n->left), findHeight(n->right)); } } Pretty standard recursive treeHeight function for a given binary search tree binaryTree. Now, I was helping a friend (he's taking an algorithms course), and I ran into some weird issue with this function that I couldn't 100% explain to him. With max being defined as max(a,b) ((a)>(b)?(a):(b)) (which happens to be the max definition in windef.h), the recursive function freaks out (it runs something like n^n times where n is the tree height). This obviously makes checking the height of a tree with 3000 elements take very, very long. However, if max is defined via templating, like std does it, everything is okay. So using std::max fixed his problem. I just want to know why. Also, why does the countLeaves function work fine, using the same programmatic recursion? int binaryTree::countLeaves(node *n) { if (n == NULL) { return 0; } else if (n->left == NULL && n->right == NULL) { return 1; } else { return countLeaves(n->left) + countLeaves(n->right); } } Is it because in returning the ternary function, the values a => countLeaves(n->left) and b => countLeaves(n->right) were recursively double called simply because they were the resultants? Thank you!

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  • How to scrape the first paragraph from a wikipedia page?

    - by David
    Let's say I want to grab the first paragraph in this wikipedia page. How do I get the principal text between the title and contents box using XPath or DOM & PHP or something similar? Is there any php library for that? I don't want to use the api because it's a bit complex. Note: i just need that to add a widget under my pages that displays related info from Wikipedia.

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  • Using ASP.NET Redirect without string URL?

    - by David Dietrich
    For instance, what I have right now is the following: Page.Response.Redirect("Default.aspx", false); Needing to hardcode the string just seems odd to me. The Default.aspx page is already in my project. So is there a way to do the redirect something like the following: Page.Response.Redirect(Default.aspx, false); Where Default.aspx is just the web form. I'd think that this way it would be obvious if there was a problem such as you deleted the web form but didn't update the redirects. Is this possible? Or is there another way entirely I should be looking at this? I suppose I could do something with a static property on the class, but I am wondering if there is a built in thing for this?

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  • C# graphics flickering

    - by David
    Hello, I am working on kind of drawing program but I have a problem with flickering while moving a mouse cursor while drawing a rubberband line. I hope you can help me to remove that flickering of line, here is the code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace GraphicsTest { public partial class Form1 : Form { int xFirst, yFirst; Bitmap bm = new Bitmap(1000, 1000); Graphics bmG; Graphics xG; Pen pen = new Pen(Color.Black, 1); bool draw = false; public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { bmG = Graphics.FromImage(bm); xG = this.CreateGraphics(); bmG.Clear(Color.White); } private void Form1_MouseDown(object sender, MouseEventArgs e) { xFirst = e.X; yFirst = e.Y; draw = true; } private void Form1_MouseUp(object sender, MouseEventArgs e) { bmG.DrawLine(pen, xFirst, yFirst, e.X, e.Y); draw = false; xG.DrawImage(bm, 0, 0); } private void Form1_MouseMove(object sender, MouseEventArgs e) { if (draw) { xG.DrawImage(bm, 0, 0); xG.DrawLine(pen, xFirst, yFirst, e.X, e.Y); } } private void Form1_Paint(object sender, PaintEventArgs e) { xG.DrawImage(bm, 0, 0); } } }

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