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  • Advice on networking career

    - by fmysky
    Hello! I need some insights on a networking career. I have a valid CCNA and few months of experience as a Jr. network analyst. My focus is a type of job where I can administer networking/storage hardware and possibly managing servers/workstations too. I am new to this job area, specifically new to city like LA. I am currently unemployed and so, my question is: should I continue with my cisco certifications(routing/wireless) or other comptia certs or both to get a reliable job? I am really interested in CCNA wireless but watching craigslist(LA) and other job sites, it seems people need more cisco voice people. While, some others also ask for Net+ certs. I have scarce financial sources so, its better to make some good decisions. I have not been applying yet due to some personal problems but I will soon. Thank you! P.S. I don't know if I can ask questions like this here. Sorry about that.

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  • Is there a simple way for opening one (or many) opengl window in mac OS X with C++ ?

    - by Petruza
    Yes, I hate Objective-c, plus my project will be portable, so I'd like to code as much of it in C++ as possible, ideally 100%. So I have a regular C++ project made with Xcode, and want to open some OpenGL windows. edit: Damn, Glut takes over the app's control with glutMainLoop(), pretty much as SDL does, I'm trying to break free from that schemes. Will try freeglut, although I can't find OSX binaries, and I always have such bad luck trying to compile someone else's code.

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  • .htaccess help to RewriteRule

    - by NeoNmaN
    Hello all I have a problem, suprice ;) i use .htaccess in Apache and have a RewriteRule problem my code is RewriteRule ^(.*)$ /system/header_codes.php?oldurl=$1 how can i make if its not have a true ( rewriterule ) soe use this, i will use its becures i create a dyanmic RewriteRule for my customer in my System. i hobe for help here, sorry for bad spelling.

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  • Can rpmbuild ingore files in buildroot?

    - by Noah Campbell
    I have a target directory that is checked into svn. I use the target as the --buildroot when I run rpmbuild. This causes rpmbuild to loose it mind because of the .svn directories in each directory. Is there a way to tell rpmbuild to relax? I looked at svn export target target-build, but it only knows about files tracked by rpm. Perhaps not a bad way to do it, but I'm not quite sure that is the best way.

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  • Filter chain halted as [:login_required] rendered_or_redirected

    - by Magicked
    Hopefully I can explain this well enough, but please let me know if more information is needed! I'm building a form where a user can create an "incident". This incident has the following relationships: belongs_to: customer (customer has_many incidents) belongs_to: user (user has_many incidents) has_one: incident_status (incident_status belongs to incident) The form allows the user to assign the incident to a user (select form) and then select an incident status. The incident is nested in customer. However, I'm getting the following in the server logs: Processing IncidentsController#create (for 127.0.0.1 at 2010-04-26 10:41:33) [POST] Parameters: {"commit"=>"Create", "action"=>"create", "authenticity_token"=>"YhW++vd/dnLoNV/DSl1DULcaWq/RwP7jvLOVx9jQblA=", "customer_id"=>"4", "controller"=>"incidents", "incident"=>{"title"=>"Some Bad Incident", "incident_status_id"=>"1", "user_id"=>"2", "other_name"=>"SS01-042310-001"}} User Load (0.3ms) SELECT * FROM "users" WHERE ("users"."id" = 2) LIMIT 1 Redirected to http://localhost:3000/session/new Filter chain halted as [:login_required] rendered_or_redirected. Completed in 55ms (DB: 0) | 302 Found [http://localhost/customers/4/incidents] It looks to me like it's trying to gather information about the user, even though it already has the id (which is all it needs to create the incident), and the user may not have permission to do a select statement like that? I'm rather confused. Here is the relevant (I think) information in the Incident controller. before_filter :login_required, :get_customer def new @incident = @customer.incidents.build @users = @customer.users @statuses = IncidentStatus.find(:all) respond_to do |format| format.html # new.html.erb format.xml { render :xml => @incident } end end def create @incident = @customer.incidents.build(params[:incident]) respond_to do |format| if @incident.save flash[:notice] = 'Incident was successfully created.' format.html { redirect_to(@incident) } format.xml { render :xml => @incident, :status => :created, :location => @incident } else format.html { render :action => "new" } format.xml { render :xml => @incident.errors, :status => :unprocessable_entity } end end end Just as an FYI, I am using the restful_authentication plugin. So in summary, when I submit the incident creation form, it does not save the incident because it halts. I'm still very new to rails, so my skill at diagnosing problems like this is still very bad. I'm going in circles. :) Thanks in advance for any help. Please let me know if more information is needed and I'll edit it in!

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  • format ugly c# source code

    - by Fred F.
    I found a C# game http://www.codeproject.com/KB/game/BattleField.aspx that does what I need to learn. The source code is not formatted good and hard to follow. I used visual studios format document, but the format is still bad. How do I reformat the source code to make it easer to read?

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  • Django: How to get current user in admin forms

    - by lazerscience
    In Django's ModelAdmin I need to display forms customized according to the permissions an user has. Is there a way of getting the current user object into the form class, so that i can customize the form in its __init__ method? I think saving the current request in a thread local would be a possibility but this would be my last resort think I'm thinking it is a bad design approach....

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  • Haskell newbie on types

    - by garulfo
    I'm completely new to Haskell (and more generally to functional programming), so forgive me if this is really basic stuff. To get more than a taste, I try to implement in Haskell some algorithmic stuff I'm working on. I have a simple module Interval that implements intervals on the line. It contains the type data Interval t = Interval t t the helper function makeInterval :: (Ord t) => t -> t -> Interval t makeInterval l r | l <= r = Interval l r | otherwise = error "bad interval" and some utility functions about intervals. Here, my interest lies in multidimensional intervals (d-intervals), those objects that are composed of d intervals. I want to separately consider d-intervals that are the union of d disjoint intervals on the line (multiple interval) from those that are the union of d interval on d separate lines (track interval). With distinct algorithmic treatments in mind, I think it would be nice to have two distinct types (even if both are lists of intervals here) such as import qualified Interval as I -- Multilple interval newtype MInterval t = MInterval [I.Interval t] -- Track interval newtype TInterval t = TInterval [I.Interval t] to allow for distinct sanity checks, e.g. makeMInterval :: (Ord t) => [I.Interval t] -> MInterval t makeMInterval is = if foldr (&&) True [I.precedes i i' | (i, i') <- zip is (tail is)] then (MInterval is) else error "bad multiple interval" makeTInterval :: (Ord t) => [I.Interval t] -> TInterval t makeTInterval = TInterval I now get to the point, at last! But some functions are naturally concerned with both multiple intervals and track intervals. For example, a function order would return the number of intervals in a multiple interval or a track interval. What can I do? Adding -- Dimensional interval data DInterval t = MIntervalStuff (MInterval t) | TIntervalStuff (TInterval t) does not help much, since, if I understand well (correct me if I'm wrong), I would have to write order :: DInterval t -> Int order (MIntervalStuff (MInterval is)) = length is order (TIntervalStuff (TInterval is)) = length is and call order as order (MIntervalStuff is) or order (TIntervalStuff is) when is is a MInterval or a TInterval. Not that great, it looks odd. Neither I want to duplicate the function (I have many functions that are concerned with both multiple and track intevals, and some other d-interval definitions such as equal length multiple and track intervals). I'm left with the feeling that I'm completely wrong and have missed some important point about types in Haskell (and/or can't forget enough here about OO programming). So, quite a newbie question, what would be the best way in Haskell to deal with such a situation? Do I have to forget about introducing MInterval and TInterval and go with one type only? Thanks a lot for your help, Garulfo

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  • To static or not to static

    - by Idsa
    I really like to use static methods (especially for helpers classes). But as static methods are not stubbable, eventually they are a bad practice, aren't they? So I have to choose between static methods usage convenience and testability. Is there any compromise?

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  • How can I add headers to DualList control wpf

    - by devnet247
    Hi all I am trying to write a Dual List usercontrol in wpf. I am new to wpf and I am finding it quite difficult. This is something I have put together in a couple of hours.It's not that good but a start. I would be extremely grateful if somebody with wpf experience could improve it. The aim is to simplify the usage as much as possible I am kind of stuck. I would like the user of the DualList Control to be able to set up headers how do you do that. Do I need to expose some dependency properties in my control? At the moment when loading the user has to pass a ObservableCollection is there a better way? Could you have a look and possibly make any suggestions with some code? Thanks a lot!!!!! xaml <Grid ShowGridLines="False"> <Grid.ColumnDefinitions> <ColumnDefinition Width="*"/> <ColumnDefinition Width="25px"></ColumnDefinition> <ColumnDefinition Width="*"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="*"></RowDefinition> </Grid.RowDefinitions> <StackPanel Orientation="Vertical" Grid.Column="0" Grid.Row="0"> <Label Name="lblLeftTitle" Content="Available"></Label> <ListView Name="lvwLeft"> </ListView> </StackPanel> <WrapPanel Grid.Column="1" Grid.Row="0"> <Button Name="btnMoveRight" Content=">" Width="25" Margin="0,35,0,0" Click="btnMoveRight_Click" /> <Button Name="btnMoveAllRight" Content=">>" Width="25" Margin="0,05,0,0" Click="btnMoveAllRight_Click" /> <Button Name="btnMoveLeft" Content="&lt;" Width="25" Margin="0,25,0,0" Click="btnMoveLeft_Click" /> <Button Name="btnMoveAllLeft" Content="&lt;&lt;" Width="25" Margin="0,05,0,0" Click="btnMoveAllLeft_Click" /> </WrapPanel> <StackPanel Orientation="Vertical" Grid.Column="2" Grid.Row="0"> <Label Name="lblRightTitle" Content="Selected"></Label> <ListView Name="lvwRight"> </ListView> </StackPanel> </Grid> Client public partial class DualListTest { public ObservableCollection<ListViewItem> LeftList { get; set; } public ObservableCollection<ListViewItem> RightList { get; set; } public DualListTest() { InitializeComponent(); LoadCustomers(); LoadDualList(); } private void LoadDualList() { dualList1.Load(LeftList, RightList); } private void LoadCustomers() { //Pretend we are getting a list of Customers from a repository. //Some go in the left List(Good Customers) some go in the Right List(Bad Customers). LeftList = new ObservableCollection<ListViewItem>(); RightList = new ObservableCollection<ListViewItem>(); var customers = GetCustomers(); foreach (var customer in customers) { if (customer.Status == CustomerStatus.Good) { LeftList.Add(new ListViewItem { Content = customer }); } else { RightList.Add(new ListViewItem{Content=customer }); } } } private static IEnumerable<Customer> GetCustomers() { return new List<Customer> { new Customer {Name = "Jo Blogg", Status = CustomerStatus.Good}, new Customer {Name = "Rob Smith", Status = CustomerStatus.Good}, new Customer {Name = "Michel Platini", Status = CustomerStatus.Good}, new Customer {Name = "Roberto Baggio", Status = CustomerStatus.Good}, new Customer {Name = "Gio Surname", Status = CustomerStatus.Bad}, new Customer {Name = "Diego Maradona", Status = CustomerStatus.Bad} }; } } UserControl public partial class DualList:UserControl { public ObservableCollection<ListViewItem> LeftListCollection { get; set; } public ObservableCollection<ListViewItem> RightListCollection { get; set; } public DualList() { InitializeComponent(); } public void Load(ObservableCollection<ListViewItem> leftListCollection, ObservableCollection<ListViewItem> rightListCollection) { LeftListCollection = leftListCollection; RightListCollection = rightListCollection; lvwLeft.ItemsSource = leftListCollection; lvwRight.ItemsSource = rightListCollection; EnableButtons(); } public static DependencyProperty LeftTitleProperty = DependencyProperty.Register("LeftTitle", typeof(string), typeof(Label)); public static DependencyProperty RightTitleProperty = DependencyProperty.Register("RightTitle", typeof(string), typeof(Label)); public static DependencyProperty LeftListProperty = DependencyProperty.Register("LeftList", typeof(ListView), typeof(DualList)); public static DependencyProperty RightListProperty = DependencyProperty.Register("RightList", typeof(ListView), typeof(DualList)); public string LeftTitle { get { return (string)lblLeftTitle.Content; } set { lblLeftTitle.Content = value; } } public string RightTitle { get { return (string)lblRightTitle.Content; } set { lblRightTitle.Content = value; } } public ListView LeftList { get { return lvwLeft; } set { lvwLeft = value; } } public ListView RightList { get { return lvwRight; } set { lvwRight = value; } } private void EnableButtons() { if (lvwLeft.Items.Count > 0) { btnMoveRight.IsEnabled = true; btnMoveAllRight.IsEnabled = true; } else { btnMoveRight.IsEnabled = false; btnMoveAllRight.IsEnabled = false; } if (lvwRight.Items.Count > 0) { btnMoveLeft.IsEnabled = true; btnMoveAllLeft.IsEnabled = true; } else { btnMoveLeft.IsEnabled = false; btnMoveAllLeft.IsEnabled = false; } if (lvwLeft.Items.Count != 0 || lvwRight.Items.Count != 0) return; btnMoveLeft.IsEnabled = false; btnMoveAllLeft.IsEnabled = false; btnMoveRight.IsEnabled = false; btnMoveAllRight.IsEnabled = false; } private void MoveRight() { while (lvwLeft.SelectedItems.Count > 0) { var selectedItem = (ListViewItem)lvwLeft.SelectedItem; LeftListCollection.Remove(selectedItem); RightListCollection.Add(selectedItem); } lvwRight.ItemsSource = RightListCollection; lvwLeft.ItemsSource = LeftListCollection; EnableButtons(); } private void MoveAllRight() { while (lvwLeft.Items.Count > 0) { var item = (ListViewItem)lvwLeft.Items[lvwLeft.Items.Count - 1]; LeftListCollection.Remove(item); RightListCollection.Add(item); } lvwRight.ItemsSource = RightListCollection; lvwLeft.ItemsSource = LeftListCollection; EnableButtons(); } private void MoveAllLeft() { while (lvwRight.Items.Count > 0) { var item = (ListViewItem)lvwRight.Items[lvwRight.Items.Count - 1]; RightListCollection.Remove(item); LeftListCollection.Add(item); } lvwRight.ItemsSource = RightListCollection; lvwLeft.ItemsSource = LeftListCollection; EnableButtons(); } private void MoveLeft() { while (lvwRight.SelectedItems.Count > 0) { var selectedCustomer = (ListViewItem)lvwRight.SelectedItem; LeftListCollection.Add(selectedCustomer); RightListCollection.Remove(selectedCustomer); } lvwRight.ItemsSource = RightListCollection; lvwLeft.ItemsSource = LeftListCollection; EnableButtons(); } private void btnMoveLeft_Click(object sender, RoutedEventArgs e) { MoveLeft(); } private void btnMoveAllLeft_Click(object sender, RoutedEventArgs e) { MoveAllLeft(); } private void btnMoveRight_Click(object sender, RoutedEventArgs e) { MoveRight(); } private void btnMoveAllRight_Click(object sender, RoutedEventArgs e) { MoveAllRight(); } }

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  • How can I explain to dspam that the user "brandon" is the same as "brandon@mydomain"

    - by Brandon Craig Rhodes
    I am using dspam for spam filtering by running the "dspamd" daemon under Ubuntu 9.10 and then setting up a Postfix rule that says: smtpd_recipient_restrictions = ... check_client_access pcre:/etc/postfix/dspam_everything ... where that PCRE map looks like this: /./ FILTER lmtp:[127.0.0.1]:11124 This works well, and means that all users on my system get all of their email, whether "dspam" thinks it is innocent or not, and have the option of filtering on its decisions or ignoring them. The problem comes when I want to train dspam using my email archives. After reading about the "dspam" command, I tried this on the files in my Inbox and spam boxes (which date from when I was using another filtering solution): for file in Mail/Inbox/*; do cat $file | dspam --class=innocent --source=corpus; done for file in Mail/spam/*; do cat $file | dspam --class=spam --source=corpus; done The symptom I noticed after doing all of this was that dspam was horrible at classifying spam — it couldn't find any! The problem, when I tracked it down, was that I was training the user "brandon" with the above commands, but the incoming email was instead compared against the username "brandon@mydomain", so it was running against a completely empty training database! So, what can I do to make the above commands actually train my fully-qualified email address rather than my bare username? I would like to avoid having to run "dspam" as root with a "--user" option. I would have expected that the "dspam" configuration files would have had an "append_domain" attribute or something with which to decorate local usernames with an appropriate email domain, but I can't find any such thing. When I used to use the Berkeley DB backend to "dspam", I solved this problem by creating a symlink from one of the databases to the other. :-) But that solution eventually died because the BDB backend is not thread-safe, so now I have moved to the PostgreSQL back-end and need a way to solve the problem there. And, no, the table where it keeps usernames has a UNIQUE constraint that prevents me from listing both usernames as mapping to the same ID. :-)

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  • Code Complete 2ed, composition and delegation.

    - by Arlukin
    Hi there. After a couple of weeks reading on this forum I thought it was time for me to do my first post. I'm currently rereading Code Complete. I think it's 15 years since the last time, and I find that I still can't write code ;-) Anyway on page 138 in Code Complete you find this coding horror example. (I have removed some of the code) class Emplyee { public: FullName GetName() const; Address GetAddress() const; PhoneNumber GetWorkPhone() const; ... bool IsZipCodeValid( Address address); ... private: ... } What Steve thinks is bad is that the functions are loosely related. Or has he writes "There's no logical connection between employees and routines that check ZIP codes, phone numbers or job classifications" Ok I totally agree with him. Maybe something like the below example is better. class ZipCode { public: bool IsValid() const; ... } class Address { public: ZipCode GetZipCode() const; ... } class Employee { public: Address GetAddress() const; ... } When checking if the zip is valid you would need to do something like this. employee.GetAddress().GetZipCode().IsValid(); And that is not good regarding to the Law of Demeter ([http://en.wikipedia.org/wiki/Law_of_Demeter][1]). So if you like to remove two of the three dots, you need to use delegation and a couple of wrapper functions like this. class ZipCode { public: bool IsValid(); } class Address { public: ZipCode GetZipCode() const; bool IsZipCodeValid() {return GetZipCode()->IsValid()); } class Employee { public: FullName GetName() const; Address GetAddress() const; bool IsZipCodeValid() {return GetAddress()->IsZipCodeValid()); PhoneNumber GetWorkPhone() const; } employee.IsZipCodeValid(); But then again you have routines that has no logical connection. I personally think that all three examples in this post are bad. Is it some other way that I haven't thougt about? //Daniel

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  • Using Valgrind tool how can I detect which object trying to access 0x0 address ?

    - by Davit Siradeghyan
    I have this output when trying to debug Program received signal SIGSEGV, Segmentation fault 0x43989029 in std::string::compare (this=0x88fd430, __str=@0xbfff9060) at /home/devsw/tmp/objdir/i686-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:253 253 { return memcmp(__s1, __s2, __n); } Current language: auto; currently c++ Using valgrind I getting this output ==12485== Process terminating with default action of signal 11 (SIGSEGV) ==12485== Bad permissions for mapped region at address 0x0 ==12485== at 0x1: (within path_to_my_executable_file/executable_file)

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  • Best practices for model driven development using LiveCycle Data Services

    - by Adnan
    What are your advises on using model driven development in developing enterprise applications. Adobe's LiveCycle Data Services looks very promising, I have found numerous tutorials/videos that shows how fast an application can be build by having methods/functions auto-generated. What are the best-practices, is it good/bad to use those auto-generated methods, they can really save a lot of time. All suggestions are welcome, also if you know some existing blog/discussion please let me know.

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  • What Issue Tracking System to select?

    - by Mikee
    What Issue Tracking Sytem is the most appropriate for fast, big, multilingual and international websites? The system has to handle both technical and content/editorial issues. What's the size and type of your site do you run? Whart System are you using for the keeping it state of the art? Thanks a lot for sharing your good or bad experience.

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  • How to send raw data over a network?

    - by youllknow
    Hi everyone! I've same data stored in a byte-array. The data contains a IPv4 packet (which contains a udp-packet). I want to send these array raw over the network using C# (preferred) or C++. I don't want to use C#'s udp-client for example. Does anyone know how to perform this? Sorry for my bad English and thanks for your help in advance!!!

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  • how to Install SproutCore 1.0 on Ubuntu 9.10

    - by Leif
    I am trying to intall SproutCore, but it doesn't work. I followed the instructions in How to Install SproutCore in Virtual Enviroment but after the installation I cant start sc in the commandline. So, I hope you understand, because my English is very bad... greetings, Leif

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  • Could MacRuby / HotCocoa supplant the need to know Objective-C?

    - by frou
    I just discovered MacRuby / HotCocoa and really like the sound of what they're doing. I had essentially discounted the prospect of making Cocoa GUI applications myself because I have an aversion to spending time & effort learning yet another C-based language, Objective-C. I'm not saying it's bad, just not for me. Is it the case now, or in the probable future, that one will be able to make Cocoa GUI applications of substantial and first-class nature with MacRuby / HotCocoa alone while ignoring Objective-C completely?

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  • A simple way to implement pathfinding using bullet physics - iPhone SDK

    - by Dave
    Hi, I have bullet physics set up and working on the iPhone but now I want to implement some sort of path finding with it. The problem is I have no idea where to start, the level is pretty simple just a lot of pillars that I want the 'bad guys' to navigate around to get to the player character. Do you have any suggestions or are there any tutorials you recommend for pathfinding using this on the iPhone?

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  • Singleton: How should it be used

    - by Loki Astari
    Edit: From another question I provided an answer that has links to a lot of questions/answers about singeltons: More info about singletons here: So I have read the thread Singletons: good design or a crutch? And the argument still rages. I see Singletons as a Design Pattern (good and bad). The problem with Singleton is not the Pattern but rather the users (sorry everybody). Everybody and their father thinks they can implement one correctly (and from the many interviews I have done, most people can't). Also because everybody thinks they can implement a correct Singleton they abuse the Pattern and use it in situations that are not appropriate (replacing global variables with Singletons!). So the main questions that need to be answered are: When should you use a Singleton How do you implement a Singleton correctly My hope for this article is that we can collect together in a single place (rather than having to google and search multiple sites) an authoritative source of when (and then how) to use a Singleton correctly. Also appropriate would be a list of Anti-Usages and common bad implementations explaining why they fail to work and for good implementations their weaknesses. So get the ball rolling: I will hold my hand up and say this is what I use but probably has problems. I like "Scott Myers" handling of the subject in his books "Effective C++" Good Situations to use Singletons (not many): Logging frameworks Thread recycling pools /* * C++ Singleton * Limitation: Single Threaded Design * See: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf * For problems associated with locking in multi threaded applications * * Limitation: * If you use this Singleton (A) within a destructor of another Singleton (B) * This Singleton (A) must be fully constructed before the constructor of (B) * is called. */ class MySingleton { private: // Private Constructor MySingleton(); // Stop the compiler generating methods of copy the object MySingleton(MySingleton const& copy); // Not Implemented MySingleton& operator=(MySingleton const& copy); // Not Implemented public: static MySingleton& getInstance() { // The only instance // Guaranteed to be lazy initialized // Guaranteed that it will be destroyed correctly static MySingleton instance; return instance; } }; OK. Lets get some criticism and other implementations together. :-)

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  • Should I enabled 802.3x hardware flow control?

    - by Stu Thompson
    What is the conventional wisdom regarding 802.3x flow control? I'm setting up a network at a new colo and am wondering if I should be enabling it or not. My oh-cool-a-bright-and-shiny-new-toy self wants to enable it, but this seems like one of those decisions that could blow up in my face later on. My network: An HP ProCurve 2510G-24 switch A pair of Debian 5 HP DL380 G5's with built-in NC373i 2-port NIC LACP'd as one link. 9000 jumbo frames enabled. (Application) A pair of hand-built Ubuntu server with 4-port Intel Pro/1000 LACP'd as one link. 9000 jumbo frames enabled. (NAS) A few other servers with with single 1Gbps ports, but one with 100Mbps. Most of this kit is 802.3x. I've been enabling it as I go along, and am about to test the network. But as my 'go live' day nears, I am worried about the 802.3x decision as I've never explicitly used it before. Also, I've read some 10-year old articles out there on the Intertubes that warn against using flow control. Should I be enabling 802.3x hardware flow control?

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  • Why isn't my query using any indices when I use a subquery?

    - by sfussenegger
    I have the following tables (removed columns that aren't used for my examples): CREATE TABLE `person` ( `id` int(11) NOT NULL, `name` varchar(1024) NOT NULL, `sortname` varchar(1024) NOT NULL, PRIMARY KEY (`id`), KEY `sortname` (`sortname`(255)), KEY `name` (`name`(255)) ); CREATE TABLE `personalias` ( `id` int(11) NOT NULL, `person` int(11) NOT NULL, `name` varchar(1024) NOT NULL, PRIMARY KEY (`id`), KEY `person` (`person`), KEY `name` (`name`(255)) ) Currently, I'm using this query which works just fine: select p.* from person p where name = 'John Mayer' or sortname = 'John Mayer'; mysql> explain select p.* from person p where name = 'John Mayer' or sortname = 'John Mayer'; +----+-------------+-------+-------------+---------------+---------------+---------+------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------------+---------------+---------------+---------+------+------+----------------------------------------------+ | 1 | SIMPLE | p | index_merge | name,sortname | name,sortname | 767,767 | NULL | 3 | Using sort_union(name,sortname); Using where | +----+-------------+-------+-------------+---------------+---------------+---------+------+------+----------------------------------------------+ 1 row in set (0.00 sec) Now I'd like to extend this query to also consider aliases. First, I've tried using a join: select p.* from person p join personalias a where p.name = 'John Mayer' or p.sortname = 'John Mayer' or a.name = 'John Mayer'; mysql> explain select p.* from person p join personalias a on p.id = a.person where p.name = 'John Mayer' or p.sortname = 'John Mayer' or a.name = 'John Mayer'; +----+-------------+-------+--------+-----------------------+---------+---------+-------------------+-------+-----------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-----------------------+---------+---------+-------------------+-------+-----------------+ | 1 | SIMPLE | a | ALL | ref,name | NULL | NULL | NULL | 87401 | Using temporary | | 1 | SIMPLE | p | eq_ref | PRIMARY,name,sortname | PRIMARY | 4 | musicbrainz.a.ref | 1 | Using where | +----+-------------+-------+--------+-----------------------+---------+---------+-------------------+-------+-----------------+ 2 rows in set (0.00 sec) This looks bad: no index, 87401 rows, using temporary. Using temporary only appears when I use distinct, but as an alias might be the same as the name, I can't really get rid of it. Next, I've tried to replace the join with a subquery: select p.* from person p where p.name = 'John Mayer' or p.sortname = 'John Mayer' or p.id in (select person from personalias a where a.name = 'John Mayer'); mysql> explain select p.* from person p where p.name = 'John Mayer' or p.sortname = 'John Mayer' or p.id in (select id from personalias a where a.name = 'John Mayer'); +----+--------------------+-------+----------------+------------------+--------+---------+------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+-------+----------------+------------------+--------+---------+------+--------+-------------+ | 1 | PRIMARY | p | ALL | name,sortname | NULL | NULL | NULL | 540309 | Using where | | 2 | DEPENDENT SUBQUERY | a | index_subquery | person,name | person | 4 | func | 1 | Using where | +----+--------------------+-------+----------------+------------------+--------+---------+------+--------+-------------+ 2 rows in set (0.00 sec) Again, this looks pretty bad: no index, 540309 rows. Interestingly, both queries (select p.* from person ... or p.id in (4711,12345) and select id from personalias a where a.name = 'John Mayer') work extremely well. Why doesn't MySQL use any indices for both of my queries? What else could I do? Currently, it looks best to fetch person.ids for aliases and add them statically as an in(...) to the second query. There certainly has to be another way to do this with a single query. I'm currently out of ideas though. Could I somehow force MySQL into using another (better) query plan?

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  • Best way to handle multiple tables to replace one big table in Rails? (e.g. 'Books1', 'Books2', etc.

    - by mikep
    Hello, I've decided to use multiple tables for an entity (e.g. Books1, Books2, Books3, etc.), instead of just one main table which could end up having a lot of rows (e.g. just Books). I'm doing this to try and to avoid a potential future performance drop that could come with having too many rows in one table. With that, I'm looking for a good way to handle this in Rails, mainly by trying to avoid loading a bunch of unused associations. (I know that I could use a partition for this, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. I'm going to split the adds across the tables. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end class Books3 < ActiveRecord::Base belongs_to :user end I'm assuming that the main performance hit would come in terms of memory and possibly some method call overhead for each User object, since it has to load all of those associations, which in turn creates all of those nice, dynamic model accessor methods like User.find_by_. But for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. For example, with a user.id of 2, I'd only need books3.find_by_author('Author'), but the way I'm thinking of setting this up, I'd still have access to Books1..n. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. So, a few questions: 1) Is there's some sort of special Ruby/Rails methodology that could be applied to this 'multiple tables to represent one entity' scheme? Are there any 'best practices' for this? 2) Is it really bad to have so many unused has_many associations for each object? Is there a better way to do this? 3) Does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class? For example, so I can call books.find_by_author('Author') instead of books3.find_by_author('Author'). Thank you!

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