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  • What is the proper way to use a Logger in a Serializable Java class?

    - by Tim Visher
    I have the following (doctored) class in a system I'm working on and Findbugs is generating a SE_BAD_FIELD warning and I'm trying to understand why it would say that before I fix it in the way that I thought I would. The reason I'm confused is because the description would seem to indicate that I had used no other non-serializable instance fields in the class but bar.model.Foo is also not serializable and used in the exact same way (as far as I can tell) but Findbugs generates no warning for it. import bar.model.Foo; import java.io.File; import java.io.Serializable; import java.util.List; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class Demo implements Serializable { private final Logger logger = LoggerFactory.getLogger(this.getClass()); private final File file; private final List<Foo> originalFoos; private Integer count; private int primitive = 0; public Demo() { for (Foo foo : originalFoos) { this.logger.debug(...); } } ... } My initial blush at a solution is to get a logger reference from the factory right as I use it: public DispositionFile() { Logger logger = LoggerFactory.getLogger(this.getClass()); for (Foo foo : originalFoos) { this.logger.debug(...); } } That doesn't seem particularly efficient, though. Thoughts?

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  • ScriptManager duplicates javascript

    - by Andreas
    Hi! I have a usercontrol that can be used in for example a gridview itemtemplate, this means that the control might or might not be on the page at page load. In the case where the control is inside an itemtemplate i will popupate the gridview via asyncronous postbacks (via updatepanels). The control itselfs registrers scriptblocks since it is depending on javascripts. First i used Page.ClientScript.RegistrerClientScriptBlock But this doesn't work on asyncronous postbacks (updatepanels) so i then tried the same using ScriptManager which allows me to registrer scripts on the page after async postbacks. great!. ScriptManager.RegisterClientScriptBlock However, ScriptManager (what i know of) does not have the functionallity to see if a script already is on the page, so i will for every postback generate duplicates of the script blocks, this is ofcourse unwanted behaviour. I did a run at Google and found that i can call the Dispose() method of the PageRequestManager can be used, this does work since it clears the scripts and then adding them again (this also solves my issue with removing unused script blocks from removed controls). Sys.WebForms.PageRequestManager.getInstance().Dispose() However, ofcourse there is a downside since im posting here :). The Dispose() method disposes the instance on the master page as well which leads to scripts running there will stop to function after an async postback (updateprogress for example). So, is there a way to check if a script already exists on the page using ScriptManager or any other tools, that will prevent me of inserting duplicate scripts? Also, is there a way to remove certain script blocks (when i am removing an item in itemtemplate for example). Big thanks in advance.

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  • Why does GetWindowThreadProcessId return 0 when called from a service

    - by Marve
    When using the following class in a console application, and having at least one instance of Notepad running, GetWindowThreadProcessId correctly returns a non-zero thread id. However, if the same code is included in a Windows Service, GetWindowThreadProcessId always returns 0 and no exceptions are thrown. Changing the user the service launches under to be the same as the one running the console application didn't alter the result. What causes GetWindowThreadProcessId to return 0 even if it is provided with a valid hwnd? And why does it function differently in the console application and the service? Note: I am running Windows 7 32-bit and targeting .NET 3.5. public class TestClass { [DllImport("user32.dll")] static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId); public void AttachToNotepad() { var processesToAttachTo = Process.GetProcessesByName("Notepad") foreach (var process in processesToAttachTo) { var threadID = GetWindowThreadProcessId(process.MainWindowHandle, IntPtr.Zero); .... } } } Console Code: class Program { static void Main(string[] args) { var testClass = new TestClass(); testClass.AttachToNotepad(); } } Service Code: public class TestService : ServiceBase { private TestClass testClass = new TestClass(); static void Main() { ServiceBase.Run(new TestService()); } protected override void OnStart(string[] args) { testClass.AttachToNotepad(); base.OnStart(args); } protected override void OnStop() { ... } }

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  • Passing variable from main to Async class

    - by Bigflow
    Somehow, I can't get this done. This is all what I tried till now: Main: private String myState; public String getState() { return myState; } public void setState(String s) { myState = s; } Async: Main appState = ((Main)getApplicationContext()); String state = appState.getState(); Error: No enclosing instance of the type Main is accessible in scope Tried with Helper(Globals) class. public class Globals extends Application{ private String test= "1"; } Main: private Globals mGlobals; mGlobals = new Globals(); mGlobals.test = "2"; //Do Async thing Async: private Globals mGlobals; mGlobals = new Globals(); print mGlobals.test; // (result is 1, should be 2) Also something else, but don't remember good. Tried alot of things (backspace and del buttons are over-used :p ) But I can't get everything working. Async class doesn't have an activity. Code pasted: http://pastebin.com/ikcsdL1p

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  • C# struct with object as data member

    - by source-energy
    As we know, in C# structs are passed by value, not by reference. So if I have a struct with the following data members: private struct MessageBox { // data members private DateTime dm_DateTimeStamp; // a struct type private TimeSpan dm_TimeSpanInterval; // also a struct private ulong dm_MessageID; // System.Int64 type, struct private String dm_strMessage; // an object (hence a reference is stored here) // more methods, properties, etc ... } So when a MessageBox is passed as a parameter, a COPY is made on the stack, right? What does that mean in terms of how the data members are copied? The first two are struct types, so copies should be made of DateTime and TimeSpan. The third type is a primitive, so it's also copied. But what about the dm_strMessage, which is a reference to an object? When it's copied, another reference to the same String is created, right? The object itself resides in the heap, and is NOT copied (there is only one instance of it on the heap.) So now we have to references to the same object of type String. If the two references are accessed from different threads, it's conceivable that the String object could be corrupted by being modified from two different directions simultaneously. The MSDN documentation says that System.String is thread safe. Does that mean that the String class has a built-in mechanism to prevent an object being corrupted in exactly the type of situation described here? I'm trying to figure out if my MessageBox struct has any potential flaws / pitfalls being a structure vs. a class. Thanks for any input. Source.Energy.

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  • How are declared private ivars different from synthesized ivars?

    - by lemnar
    I know that the modern Objective-C runtime can synthesize ivars. I thought that synthesized ivars behaved exactly like declared ivars that are marked @private, but they don't. As a result, come code compiles only under the modern runtime that I expected would work on either. For example, a superclass: @interface A : NSObject { #if !__OBJC2__ @private NSString *_c; #endif } @property (nonatomic, copy) NSString *d; @end @implementation A @synthesize d=_c; - (void)dealloc { [_c release]; [super dealloc]; } @end and a subclass: @interface B : A { #if !__OBJC2__ @private NSString *_c; #endif } @property (nonatomic, copy) NSString *e; @end @implementation B @synthesize e=_c; - (void)dealloc { [_c release]; [super dealloc]; } @end A subclass can't have a declared ivar with the same name as one of its superclass's declared ivars, even if the superclass's ivar is private. This seems to me like a violation of the meaning of @private, since the subclass is affected by the superclass's choice of something private. What I'm more concerned about, however, is how should I think about synthesized ivars. I thought they acted like declared private ivars, but without the fragile base class problem. Maybe that's right, and I just don't understand the fragile base class problem. Why does the above code compile only in the modern runtime? Does the fragile base class problem exist when all superclass instance variables are private?

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  • JPA/Hibernate Parent/Child relationship

    - by NubieJ
    Hi I am quite new to JPA/Hibernate (Java in general) so my question is as follows (note, I have searched far and wide and have not come across an answer to this): I have two entities: Parent and Child (naming changed). Parent contains a list of Children and Children refers back to parent. e.g. @Entity public class Parent { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "PARENT_ID", insertable = false, updatable = false) private int id; /* ..... */ @OneToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", nullable = true) private Set<child> children; /* ..... */ } @Entity public class Child { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "CHILD_ID", insertable = false, updatable = false) private int id; /* ..... */ @ManyToOne(cascade = { CascadeType.REFRESH }, fetch = FetchType.EAGER, optional = false) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID") private Parent parent; /* ..... */ } I want to be able to do the following: Retrieve a Parent entity which would contain a list of all its children (List), however, when listing Parent (getting List, it of course should omit the children from the results, therefore setting FetchType.LAZY. Retrieve a Child entity which would contain an instance of the Parent entity. Using the code above (or similar) results in two exceptions: Retrieving Parent: A cycle is detected in the object graph. This will cause infinitely deep XML... Retrieving Child: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: xxxxxxxxxxx, no session or session was closed When retrieving the Parent entity, I am using a named query (i.e. calling it specifically) @NamedQuery(name = "Parent.findByParentId", query = "SELECT p FROM Parent AS p LEFT JOIN FETCH p.children where p.id = :id") Code to get Parent (i.e. service layer): public Parent findByParentId(int parentId) { Query query = em.createNamedQuery("Parent.findByParentId"); query.setParameter("id", parentId); return (Parent) query.getSingleResult(); } Why am I getting a LazyInitializationException event though the List property on the Parent entity is set as Lazy (when retrieving the Child entity)?

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  • Forcing Kernel::method_name to be called in Ruby

    - by Peter
    I want to add a foo method to Ruby's Kernel module, so I can write foo(obj) anywhere and have it do something to obj. Sometimes I want a class to override foo, so I do this: module Kernel private # important; this is what Ruby does for commands like 'puts', etc. def foo x if x.respond_to? :foo x.foo # use overwritten method. else # do something to x. end end end this is good, and works. but, what if I want to use the default Kernel::foo in some other object that overwrites foo? Since I've got an instance method foo, I've lost the original binding to Kernel::foo. class Bar def foo # override behaviour of Kernel::foo for Bar objects. foo(3) # calls Bar::foo, not the desired call of Kernel::foo. Kernel::foo(3) # can't call Kernel::foo because it's private. # question: how do I call Kernel::foo on 3? end end Is there any clean way to get around this? I'd rather not have two different names, and I definitely don't want to make Kernel::foo public.

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  • Seeding many to many tables with Entity Framework

    - by Doozer1979
    I have a meeting entity and a users entity which have a many to many relationship. I'm using Autopoco to create seed data for the Users and meetings How do i seed the UserMeetings linking table that is created by EntityFramework with seed data? The linking table has two fields in it; User_Id, and Meeting_ID. I'm looping through the list of users that autopoco creates and attaching a random number of meetings Here's what i've got so far. foreach (var user in userList) { var rand = new Random(); var amountOfMeetingsToAdd = rand.Next(1, 300); for (var i = 0; i <= amountOfMeetingsToAdd; i++) { var randomMeeting = rand.Next(1, MeetingRecords); //Error occurs on This line user.Meetings.Add(_meetings[randomMeeting]); } } I got an 'Object reference not set to an instance of an object.' even though the meeting record that i'm trying to attach does exist. For info all this is happening prior to me saving the context to the DB.

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  • Is there an application that can help someone create an XML document based on the Relax NG schema?

    - by meowsqueak
    I've spent a bit of time creating a Relax NG schema for use within our team to validate XML documents we use for exchanging information. The schema is not complicated, but it is reasonably large. I am wondering if there exists a tool that can read in such a Relax NG schema and assist a user in creating a corresponding instance document, using the schema as a template. Perhaps an application with a GUI that creates fields and drop-down selections for each part of the document? For example, the tool might create an outline XML document and prompt the user to select multiples of certain elements, fill in each field, perhaps with permitted values read directly from the schema. It might also show the user via visual feedback when their document is 'complete', or highlight validation problems as they come up. I could anticipate writing a custom GUI tool to create such an XML document, but I'd really like changes to the schema to be automatically reflected by the GUI - and I really wonder if this hasn't already been done. I know some editors can automatically validate an XML document against a schema as it's being written, but I would really like to get my users one step away from the XML so they don't have to worry about the details of the XML syntax.

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  • TicTacToe strategic reduction

    - by NickLarsen
    I decided to write a small program that solves TicTacToe in order to try out the effect of some pruning techniques on a trivial game. The full game tree using minimax to solve it only ends up with 549,946 possible games. With alpha-beta pruning, the number of states required to evaluate was reduced to 18,297. Then I applied a transposition table that brings the number down to 2,592. Now I want to see how low that number can go. The next enhancement I want to apply is a strategic reduction. The basic idea is to combine states that have equivalent strategic value. For instance, on the first move, if X plays first, there is nothing strategically different (assuming your opponent plays optimally) about choosing one corner instead of another. In the same situation, the same is true of the center of the walls of the board, and the center is also significant. By reducing to significant states only, you end up with only 3 states for evaluation on the first move instead of 9. This technique should be very useful since it prunes states near the top of the game tree. This idea came from the GameShrink method created by a group at CMU, only I am trying to avoid writing the general form, and just doing what is needed to apply the technique to TicTacToe. In order to achieve this, I modified my hash function (for the transposition table) to enumerate all strategically equivalent positions (using rotation and flipping functions), and to only return the lowest of the values for each board. Unfortunately now my program thinks X can force a win in 5 moves from an empty board when going first. After a long debugging session, it became apparent to me the program was always returning the move for the lowest strategically significant move (I store the last move in the transposition table as part of my state). Is there a better way I can go about adding this feature, or a simple method for determining the correct move applicable to the current situation with what I have already done?

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  • Ad distribution problem: an optimal solution?

    - by Mokuchan
    I'm asked to find a 2 approximate solution to this problem: You’re consulting for an e-commerce site that receives a large number of visitors each day. For each visitor i, where i € {1, 2 ..... n}, the site has assigned a value v[i], representing the expected revenue that can be obtained from this customer. Each visitor i is shown one of m possible ads A1, A2 ..... An as they enter the site. The site wants a selection of one ad for each customer so that each ad is seen, overall, by a set of customers of reasonably large total weight. Thus, given a selection of one ad for each customer, we will define the spread of this selection to be the minimum, over j = 1, 2 ..... m, of the total weight of all customers who were shown ad Aj. Example Suppose there are six customers with values 3, 4, 12, 2, 4, 6, and there are m = 3 ads. Then, in this instance, one could achieve a spread of 9 by showing ad A1 to customers 1, 2, 4, ad A2 to customer 3, and ad A3 to customers 5 and 6. The ultimate goal is to find a selection of an ad for each customer that maximizes the spread. Unfortunately, this optimization problem is NP-hard (you don’t have to prove this). So instead give a polynomial-time algorithm that approximates the maximum spread within a factor of 2. The solution I found is the following: Order visitors values in descending order Add the next visitor value (i.e. assign the visitor) to the Ad with the current lowest total value Repeat This solution actually seems to always find the optimal solution, or I simply can't find a counterexample. Can you find it? Is this a non-polinomial solution and I just can't see it?

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  • How to avoid hard-coded credentials in Sharepoint webpart?

    - by Bryan
    I am building a Sharepoint web part that will be used by all users, but can only be modified by admins. The web part connects to a web service which needs credentials. I hard coded credentials in the web part's code. query.Credentials = new System.Net.NetworkCredential("username", "password", "domain"); query is an instance of the web service class This may not be a good approach. In regard with security, the source code of the web apart is available to people who are not allowed to see the credentials. In normal ASP.net applications, credentials can be written into web.config and encrypted. A web part doesn't have a .config file associated. There is a application-level .config file for the whole sharepoint site, but I don't want to modify it for a single webpart. I wonder if there is a webpart-specific way to solve the credential problem? Say we provide a WebBrowsable property of that web part so that privileged users can modify credentials. If this is desirable, how should I make the property displayed in a password ("*") rather than in plain text? Thanks.

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  • What should i do for accomodating large scale data storage and retrieval?

    - by kailashbuki
    There's two columns in the table inside mysql database. First column contains the fingerprint while the second one contains the list of documents which have that fingerprint. It's much like an inverted index built by search engines. An instance of a record inside the table is shown below; 34 "doc1, doc2, doc45" The number of fingerprints is very large(can range up to trillions). There are basically following operations in the database: inserting/updating the record & retrieving the record accoring to the match in fingerprint. The table definition python snippet is: self.cursor.execute("CREATE TABLE IF NOT EXISTS `fingerprint` (fp BIGINT, documents TEXT)") And the snippet for insert/update operation is: if self.cursor.execute("UPDATE `fingerprint` SET documents=CONCAT(documents,%s) WHERE fp=%s",(","+newDocId, thisFP))== 0L: self.cursor.execute("INSERT INTO `fingerprint` VALUES (%s, %s)", (thisFP,newDocId)) The only bottleneck i have observed so far is the query time in mysql. My whole application is web based. So time is a critical factor. I have also thought of using cassandra but have less knowledge of it. Please suggest me a better way to tackle this problem.

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  • JumpLists Not Working in C# App

    - by Josh M.
    Hi, I'm trying to use the Recent and Frequent JumpLists in my C# app. I'm using the Windows API Codepack v1.1 (http://code.msdn.microsoft.com/WindowsAPICodePack). I initialize the JumpLists every time the app starts and I AddRecent() to the JumpList every time I open a project in the app. Something is missing becuase the JumpLists are simply not showing up when you right click the app's icon in the Taskbar. I got one file to show up once but that's it! Initialization: private void InitializeJumpLists() { if (TaskbarManager.IsPlatformSupported) { JumpList recentJumpList = null; JumpList frequentJumpList = null; TaskbarManager.Instance.ApplicationId = Application.ProductName; recentJumpList = JumpList.CreateJumpList(); recentJumpList.KnownCategoryToDisplay = JumpListKnownCategoryType.Recent; recentJumpList.Refresh(); frequentJumpList = JumpList.CreateJumpList(); frequentJumpList.KnownCategoryToDisplay = JumpListKnownCategoryType.Frequent; frequentJumpList.Refresh(); } } Opening the Project: private void OpenProject(string path, bool isFromRecentFilesList) { DialogResult result = ConfirmProjectClosing(); if (result == DialogResult.Yes) Save(); else if (result == DialogResult.Cancel) return; using (new Wait()) { //Code here opens the project, etc. //Try to add the file to the Jump List. if (TaskbarManager.IsPlatformSupported) JumpList.AddToRecent(path); //Code here finished up. } } What am I missing?

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  • How to check for a null object reference when validating forms in MVC

    - by quakkels
    Hello SO, I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc ) { mc.Modules = ModuleListDataContext.GetModuleList(); ViewData.Model = mc; //Validation using ModelState // // //line below errors when form field is empty // if ((string)mc.Member.Username.Trim() == "") ModelState.AddModelError("Member.Username", "Username is required."); if (!ModelState.IsValid) return View(); try { // TODO: Add insert logic here return RedirectToAction("Index","Home"); } catch { return View(); } } When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields? Thanks all -

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  • Invoking a method overloaded where all arguments implement the same interface

    - by double07
    Hello, My starting point is the following: - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below) - All these arguments implement the same interface, X I would like to apply that transform method on various objects all implementing the X interface. What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform. Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior? Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below. public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) && (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) && (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); }

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  • What are the skills a Drupal Developer needs?

    - by hfidgen
    I'm trying to write out a list of key Drupal competencies, mainly so I can confirm what I know, don't know and don't know I don't know. (Thanks D. Rumsfeld for that quote!) I think some of these are really broad, for instance there's quite a difference between making a functional theme and creating a theme with good SEO, load times and so on, but I'm hoping you could assume that a half decent web developer would look after that anyway. Just interested to see what people here feel is also important. Able to install Drupal on a server (pretty obvious). Able to research and install modules to meet project requirements Able to configure all the basic modules and core settings to get a site running Able to create a custom Theme from scratch which validates with good HTML/CSS and also pays attention to usability and accessibility. (Whilst still looking kick-ass). Able to use Hooks in the theme template.php to alter forms, page layout and other core functionality Can make forms from scratch using the API - with validation and posting back to the DB/email Can use Views to create blocks or pages, use php snippets as arguments, etc. Can create custom modules from scratch utilising core hooks and other hooks.

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  • How to authenticate multiple entry points in a facebook app?

    - by Simon_Weaver
    I am using an IFrame application with XFBML and the new Javascript API. I'd like to have a facebook application with multiple entry points. These will most likely represent different links coming from a fan page tab. I can do this quite easily if the pages don't require authentication - for instance I can create several pages under the app and if a new user comes I can send them to any page: http://apps.facebook.com/myapp/offers http://apps.facebook.com/myapp/game http://apps.facebook.com/myapp/products The problem is that if I need to have authentication then once the user is authenticated they get redirected to my default post-authorization url. Is there a way for a user that comes to /game to stay on /game after they are authenticated without redirecting. I thought I could do it with the AJAX login form - but I cannot find out how to do that in a Facebook IFrame application. I think the example using requirelogin only works for FBML. <a href="http://apps.facebook.com/mysmiley" requirelogin=1> Welcome to my app</a>. Is there a way to accomplish this with Facebook APIs - or will I have to do some kind of clever cookie handling?

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  • Gem Load Error about whois command and removed cache

    - by Puru puru rin..
    Hello, I have an awesome trouble with Gem. After executing this command: rm -f /usr/local/lib/ruby/gems/1.9.1/cache/* I can not do any thing. If I try for instance: gem cleanup I get this kind of answer: /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/gemwhois.rb:3:in `require': no such file to load -- rubygems/commands/whois (LoadError) from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/gemwhois.rb:3:in `<top (required)>' from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/rubygems_plugin.rb:2:in `require' from /usr/local/lib/ruby/gems/1.9.1/gems/gemwhois-0.1/lib/rubygems_plugin.rb:2:in `<top (required)>' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1113:in `load' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1113:in `block in <top (required)>' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1105:in `each' from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1105:in `<top (required)>' from <internal:gem_prelude>:235:in `require' from <internal:gem_prelude>:235:in `load_full_rubygems_library' from <internal:gem_prelude>:334:in `const_missing' from /usr/local/bin/gem:12:in `<main>' It's the same for gem -v, of just gem command... I'm working of Snow Leopard. What should the best solution about you? Thanks a lot!

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  • Database structure for ecommerce site

    - by imanc
    Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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  • How to design data storage for partitioned tagging system?

    - by Morgan Cheng
    How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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  • Ways of breaking down SQL transactional/call data into reports -- 'square data'?

    - by RizwanK
    I've got a large database of call-traffic information (although the question could be answered with any generic data set.) For instance, a row contains : call endpoint server (endpoint_name) call endpoint status (sip_disconnect_reason) call destination (destination) call completed (duration) [duration 0 is completed] call account group (account_group) It's pretty easy to run SQL reports against the data, i.e. select count(*), endpoint_name from calls where duration0 group by endpoint_name select count(*),destination from calls where blah group by destination I've been calling this filtering or breakdown reports (I get the number of calls per carrier, etc.). Add another breakdown, and you've got two breakdowns, a la select count(*), endpoint_name, sip_disconnect_reason from calls where duration=0 group by endpoint_name, sip_disconnect_reason Of course, if you keep adding breakdowns, you end up making super-large reports and slicing your data so thin that you can't extract any trends from it. So my question is this : Is there a name for this sort of method of report writing? (I've heard words like squares, slicing and breakdown reports applied to them) --- I'm looking for a Python/Reporting toolkit that I can use to make these easier to generate for my end users. aside : Are there other ways of representing transactional data that might be useful rather than the above method? Thanks,

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  • Trait, FunctionN, or trait-inheriting-FunctionN in Scala?

    - by Willis Blackburn
    I have a trait in Scala that has a single method. Call it Computable and the single method is compute(input: Int): Int. I can't figure out whether I should Leave it as a standalone trait with a single method. Inherit from (Int = Int) and rename "compute" to "apply." Just get rid of Computable and use (Int = Int). A factor in favor of it being a trait is that I could usefully add some additional methods. But of course if they were all implemented in terms of the compute method then I could just break them out into a separate object. A factor in favor of just using the function type is simplicity and the fact that the syntax for an anonymous function is more concise than that for an anonymous Computable instance. But then I've no way to distinguish objects that are actually Computable instances from other functions that map Int to Int but aren't meant to be used in the same context as Computable. How do other people approach this type of problem? No right or wrong answers here; I'm just looking for advice.

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  • How to get the related_name of a many-to-many-field?

    - by amann
    I am trying to get the related_name of a many-to-many-field. The m2m-field is located betweeen the models "Group" and "Lection" and is declared in the group-model as following: lections = models.ManyToManyField(Lection, blank=True) The field looks like this: <django.db.models.fields.related.ManyToManyField object at 0x012AD690> The print of field.__dict__ is: {'_choices': [], '_m2m_column_cache': 'group_id', '_m2m_name_cache': 'group', '_m2m_reverse_column_cache': 'lection_id', '_m2m_reverse_name_cache': 'lection', '_unique': False, 'attname': 'lections', 'auto_created': False, 'blank': True, 'column': 'lections', 'creation_counter': 71, 'db_column': None, 'db_index': False, 'db_table': None, 'db_tablespace': '', 'default': <class django.db.models.fields.NOT_PROVIDED at 0x00FC8780>, 'editable': True, 'error_messages': {'blank': <django.utils.functional.__proxy__ object at 0x00FC 7B50>, 'invalid_choice': <django.utils.functional.__proxy__ object at 0x00FC7A50>, 'null': <django.utils.functional.__proxy__ object at 0x00FC7 A70>}, 'help_text': <django.utils.functional.__proxy__ object at 0x012AD6F0>, 'm2m_column_name': <function _curried at 0x012A88F0>, 'm2m_db_table': <function _curried at 0x012A8AF0>, 'm2m_field_name': <function _curried at 0x012A8970>, 'm2m_reverse_field_name': <function _curried at 0x012A89B0>, 'm2m_reverse_name': <function _curried at 0x012A8930>, 'max_length': None, 'name': 'lections', 'null': False, 'primary_key': False, 'rel': <django.db.models.fields.related.ManyToManyRel object at 0x012AD6B0>, 'related': <RelatedObject: mymodel:group related to lections>, 'related_query_name': <function _curried at 0x012A8670>, 'serialize': True, 'unique_for_date': None, 'unique_for_month': None, 'unique_for_year': None, 'validators': [], 'verbose_name': 'lections'} Now the field should be accessed via a lection-instance. So this is done by lection.group_set But i need to access it dynamically, so there is the need to get the related_name attribute from somewhere. Here in the documentation, there is a note that it is possible to access ManyToManyField.related_name, but this doesn't work for my somehow.. Help would be a lot appreciated. Thanks in advance.

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