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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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  • Maintaining integrity of Core Data Entities with many incoming one-to-many relationships

    - by Henry Cooke
    Hi all. I have a Core Data store which contains a number of MediaItem entities that describe, well, media items. I also have NewsItems, which have one-to-many relationships to a number of MediaItems. So far so good. However, I also have PlayerItems and GalleryItems which also have one-to-many relationships to MediaItems. So MediaItems are shared across entities. Given that many entities may have one-to-many relationships, how can I set up reciprocal relationships from a MediaItem to all (1 or more) of the entities which have relationships to it and, furthermore, how can I implement rules to delete MediaItems when the number of those reciprocal relationships drops to 0?

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  • Database Table of Boolean Values

    - by guazz
    What's the best method of storing a large number of booleans in a database table? Should I create a column for each boolean value or is there a more optimal method? Employee Table IsHardWorking IsEfficient IsCrazy IsOverworked IsUnderpaid ...etc.

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  • Branchless memory manager?

    - by Richard Fabian
    Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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  • why is java.lang.Throwable a class?

    - by mdma
    In java adjectives ending in -able are interfaces Serializable, Comparable etc... So why is Throwable a class? Wouldn't exception handling be easier if Throwable were an interface? Obviously, changing it now is out the question. But could it be made abstract? Wouldn't that avoid the bad practice of throw new Throwable();

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  • Sequence numbers best practice

    - by Abdullah Jibaly
    What's the best practice or well known methods to implement sequence numbers for business entities such as invoices, purchase orders, job numbers, etc? I want to be able to save the latest value in the database and be able to set it programatically. Is it OK to use a table for this purpose that has a SEQUENCE_NAME, SEQUENCE_NUMBER tuple? I know some databases have a first class sequence type but others (eg, MySQL) do not so it's not something I want to rely on. If a table is used to hold these sequences what is the right way to get and increment them in a synchronized fashion to ensure no data inconsistencies arise?

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  • Usability: call for action

    - by Shyam
    I am designing a page, with tiny portlets. Now, I personally like my actions on the right side, yet I wonder if there are methodologies that are targeted about usability. After all, most applications are aimed at the user. What about yourself? Do you prefer information to be on top, on the left or on the right? I've you need to take some sort of action, do you prefer buttons on the left? References to good books and webpages are very welcome!

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  • When should I use Dependency Injection and when utility methods?

    - by Roman
    I have a Java EE project with Spring IoC container. I've just found in Utils class static method sendMail(long list of params). I don't know why but I feel that it would look better if we had separate class (Spring bean with singleton scope) which will be responsible for sending email. But I can't find any arguments which can prove my position. So, are there any pros (or cons) in using DI in this (rather general) situation?

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  • Advantage of using a static member function instead of an equivalent non-static member function?

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • How do I call exec in psake to an executable with a variable path?

    - by Josh Kodroff
    I can't seem to call this executable correctly in my psake deploy script. If I do this: exec { "$ArchiverOutputDir\NServiceBus.Host.exe /install" } It simply outputs this (and is clearly not calling the executable - just outputting the value of that expression): c:\ReloDotNet2_ServiceEndpoints\Archiver\NServiceBus.Host.exe /install But if I do this: exec { c:\ReloDotNet2_ServiceEndpoints\Archiver\NServiceBus.Host.exe /install } I get the expected output from the executable. How do I correctly call an executable with a variable in the path to the executable in psake? If this is actually a PowerShell issue, please feel free to correct the question to reflect that insight. I

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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • algorithm || method to write prog

    - by fatai
    I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • Designer tool integration with TFS?

    - by reallyJim
    Are there good tools for professional designers to use that support source control integration with Team Foundation Server? I'm aware of the Expression tools, but curious to see if there is something else, as proper designer tools really aren't my area of expertise.

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  • how to run this qt script? (newbie question)

    - by GB_J
    I have a qt script(barchart.qs) that creates a graph for me. I don't know how i can incorporate(ie show the graph) in my qt mainwindow. Can some one please help me look at the code and what its outputs are? I tried engine.evaluate, but i do not know what is the QScriptValue i'm getting in return. Thanks sooo much. This is the script: BarChart.prototype = new QWidget; BarChart.prototype.suffix = ""; function BarChart(parent) { QWidget.call(this, parent); } // find the maximum value and widest (pixel-wise) label and suffix BarChart.prototype.showEvent = function(event) { var fm = new QFontMetrics(this); this.margin = 20; this.titleHeight = fm.height(); this.barHeight = 1.5 * fm.height(); this.barSpacing = 0.6 * fm.height(); this.maxValue = this.suffixWidth = this.labelWidth = 0; var count = 0; for (d in this.data) { this.labelWidth = Math.max(this.labelWidth, fm.width(d)); this.maxValue = Math.max(this.maxValue, this.data[d]); this.suffixWidth = Math.max(this.suffixWidth, fm.width(String(this.data[d]) + " " + this.suffix)); count++; } this.startHue = 15; this.hueDelta = 360 / count; this.size = new QSize(640, this.titleHeight + 2 * this.margin + (this.barHeight + this.barSpacing) * count); } BarChart.prototype.paintEvent = function(event) { var p = new QPainter; p.begin(this); // background and title p.fillRect(this.rect, new QBrush(new QColor(255, 255, 255))); p.drawText(0, 0, this.width, this.margin + this.titleHeight, Qt.AlignCenter, this.windowTitle, 0); var ofs = this.labelWidth + this.margin; var ww = this.width - this.suffixWidth - ofs - 2 * this.margin; var hue = this.startHue; var y = 0; p.translate(this.margin, this.titleHeight + 1.5 * this.margin); for (d in this.data) { // label on the left side p.setPen(new QColor(Qt.black)); p.drawText(0, y, this.labelWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignRight, d, 0); // the colored bar var gradient = new QLinearGradient(new QPoint(ofs, y), new QPoint(ofs, y + this.barHeight)); gradient.setColorAt(0, QColor.fromHsv(hue, 255, 240)); gradient.setColorAt(1, QColor.fromHsv(hue, 255, 92)); p.setBrush(new QBrush(gradient)); p.setPen(new QColor(96, 96, 96)); var bw = this.data[d] * ww / this.maxValue; p.drawRect(ofs, y, bw, this.barHeight); // extra text at the end of the bar var text = new String(this.data[d] + " " + this.suffix); p.setPen(new QColor(Qt.black)); p.drawText(ofs + bw + this.margin/2, y, this.suffixWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignLeft, text, 0); // for the next bar y += (this.barHeight + this.barSpacing); hue += this.hueDelta; if (hue >= 360) hue -= 360; } p.end(); } BarChart.prototype.wheelEvent = function(event) { this.startHue += event.delta() / 8 / 5; if (this.startHue = 360) this.startHue -= 360; if (this.startHue < 0) this.startHue += 360; this.update(); event.ignore(); } BarChart.prototype.mousePressEvent = function(event) { var fname = QFileDialog.getSaveFileName(this, "Save", ".", "*.png", 0, 0); if (fname.length > 0) { var img = new QImage(this.size, QImage.Format_ARGB32_Premultiplied); this.render(img); img.save(new QFile(fname)); } } var chart = new BarChart; chart.windowTitle = "Monthly"; chart.suffix = "reports"; chart.data = { "September" : 45, "October" : 60, "November" : 56, "December" : 0 }; chart.show(); QCoreApplication.exec();

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  • How do I correctly model data in SQL-based databases that have some columns in common, but also have

    - by Brandon Weiss
    For instance, let's say I have a User model. Users have things like logins, passwords, e-mail addresses, avatars, etc. But there are two types of Users that will be using this site, let's say Parents and Businesses. I need to store some different information for the Parents (e.g. childrens' names, domestic partner, salaries, etc.) than for the Businesses (e.g. industry, number of employees, etc.), but also some of it is the same, like logins and passwords. How do I correctly structure this in a SQL-based database? Thanks!

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  • Validating class and superclass on RoR

    - by Luís Guilherme
    In ruby, you have an attribute called "type" which is the class of the object. Rails stores this at the database in a column called type. So, if I have several blog "types", I can do something like this def create @blog = Blog.new(params[:blog]) @blog[:type] = params[:blog][:type] # ... end If I add someone like this, and then load it, and ask its class (for instance, at the console), I have the right class name answered back. However, when I save it afterwards, rails will run only the superclass validators, not the ones I defined in the subclass. How should I make rails run the subclass validators?

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  • Proper way to set object instance variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • Multiple Tables or Multiple Schema

    - by Yan Cheng CHEOK
    http://stackoverflow.com/questions/1152405/postgresql-is-better-using-multiple-databases-with-1-schema-each-or-1-database I am new in schema concept for PostgreSQL. For the above mentioned scenario, I was wondering Why don't we use a single database (with default schema named public) Why don't we have a single table, to store multiple users row? Other tables which hold users related information, with foreign key point to the user table. Can anyone provide me a real case scenario, which single database, multiple schema will be extremely useful, and can't solve by conventional single database, single schema.

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  • Entity framework (1): implement 1 foreign key to multiple tables

    - by Michel
    Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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  • Structuring Win32 GUI code

    - by kraf
    I wish to improve my code and file structure in larger Win32 projects with plenty of windows and controls. Currently, I tend to have one header and one source file for the entire implementation of a window or dialog. This works fine for small projects, but now it has come to the point where these implementations are starting to reach 1000-2000 lines, which is tedious to browse. A typical source file of mine looks like this: static LRESULT CALLBACK on_create(const HWND hwnd, WPARAM wp, LPARAM lp) { setup_menu(hwnd); setup_list(hwnd); setup_context_menu(hwnd); /* clip */ return 0; } static LRESULT CALLBACK on_notify(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { const NMHDR* header = (const NMHDR*)lp; /* At this point I feel that the control's event handlers doesn't * necessarily belong in the same source file. Perhaps I could move * each control's creation code and event handlers into a separate * source file? Good practice or cause of confusion? */ switch (header->idFrom) { case IDC_WINDOW_LIST: switch (header->code) { case NM_RCLICK: return on_window_list_right_click(hwnd, wp, lp); /* clip */ } } } static LRESULT CALLBACK wndmain_proc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { switch (msg) { case WM_CREATE: return on_create(hwnd, wp, lp); case WM_CLOSE: return on_close(hwnd, wp, lp); case WM_NOTIFY: return on_notify(hwnd, wp, lp); /* It doesn't matter much how the window proc looks as it just forwards * events to the appropriate handler. */ /* clip */ default: return DefWindowProc(hwnd, msg, wp, lp); } } But now as the window has a lot more controls, and these controls in turn have their own message handlers, and then there's the menu click handlers, and so on... I'm getting lost, and I really need advice on how to structure this mess up in a good and sensible way. I have tried to find good open source examples of structuring Win32 code, but I just get more confused since there are hundreds of files, and within each of these files that seem GUI related, the Win32 GUI code seems so far encapsulated away. And when I finally find a CreateWindowEx statement, the window proc is nowhere to be found. Any advice on how to structure all the code while remaining sane would be greatly appreciated. Thanks! I don't wish to use any libraries or frameworks as I find the Win32 API interesting and valuable for learning. Any insight into how you structure your own GUI code could perhaps serve as inspiration.

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