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• How to structure a database with questions and answers?

  - by Andreas Johannessen

  Hi I am going to make a simple application that uses a database. I could need some guidance on how to structure it. I shall make question program. What I have in mind is. One table with questions One table with the difficulity of the question One table with the category of the question However, what do I do with the answers? Have them as seperate columns in the question-table? It sounds like a bad practice.(Also, where do I have the correct answer) Each question will have 5 answers where only one of them is correct.

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• JSON DATA formatting in WebAPI

  - by user1736299

  public class CalendarController : ApiController { Events[] events = new Events[] { new Events { title= "event1", start = System.DateTime.UtcNow, end = System.DateTime.UtcNow }, new Events { title= "event2", start = System.DateTime.UtcNow, end = System.DateTime.UtcNow }, new Events { title= "event3", start = System.DateTime.UtcNow, end = System.DateTime.UtcNow} }; public IEnumerable<Events> GetAllCalendar() { return events; } The JSON result for the above is [{ "title": "event1", "start": "2012-12-05T22:52:35.6471712Z", "end": "2012-12-05T22:52:35.6471712Z"}, { "title": "event2", "start": "2012-12-05T22:52:35.6471712Z", "end": "2012-12-05T22:52:35.6471712Z"}, { "title": "event3", "start": "2012-12-05T22:52:35.6471712Z", "end": "2012-12-05T22:52:35.6471712Z" }]? How to create the same JSON result without the double quotes but single quote. How to get the date in the format of ‘YYYY-MM-DD HH:MM:SS’ Thank you, Smith

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• array of structures, or structure of arrays?

  - by Jason S

  Hmmm. I have a table which is an array of structures I need to store in Java. The naive don't-worry-about-memory approach says do this: public class Record { final private int field1; final private int field2; final private long field3; /* constructor & accessors here */ } List<Record> records = new ArrayList<Record>(); If I end up using a large number ( 106 ) of records, where individual records are accessed occasionally, one at a time, how would I figure out how the preceding approach (an ArrayList) would compare with an optimized approach for storage costs: public class OptimizedRecordStore { final private int[] field1; final private int[] field2; final private long[] field3; Record getRecord(int i) { return new Record(field1[i],field2[i],field3[i]); } /* constructor and other accessors & methods */ } edit: assume the # of records is something that is changed infrequently or never I'm probably not going to use the OptimizedRecordStore approach, but I want to understand the storage cost issue so I can make that decision with confidence. obviously if I add/change the # of records in the OptimizedRecordStore approach above, I either have to replace the whole object with a new one, or remove the "final" keyword. kd304 brings up a good point that was in the back of my mind. In other situations similar to this, I need column access on the records, e.g. if field1 and field2 are "time" and "position", and it's important for me to get those values as an array for use with MATLAB, so I can graph/analyze them efficiently.

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• Efficient storage/retrieval method for replayable comet style applications (Google Wave, Etherpad)

  - by Gareth Simpson

  I am considering a web application that would have the same kind of multi user, automatic saving, infinite undo / replay capabilities that you see in Google Wave and Etherpad (albeit on a drastically smaller scale and userbase). Before I go away and reinvent the wheel, is this something that has already been addressed as either a piece of technology or library, or even just a design pattern. I know this isn't necessarily the best Stack Overflow question as there is probably not a "right" answer, but my Google-fu has failed me and I'd just like a reading list! Ordinarily I would be developing under python/django but this is not a firm requirement just a preference :)

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• Data not synchornizing java sockets

  - by Droid_Interceptor

  I am writing a auction server and client and using a class called BidHandler to deal with the bids another class AuctionItem to deal with the items for auction. The main problem I am having is little synchroization problem. Screen output of client server as can see from the image at 1st it takes the new bid and changes the value of the time to it, but when one the user enters 1.0 the item seems to be changed to that. But later on when the bid changes again to 15.0 it seems to stay at that price. Is there any reason for that. I have included my code below. Sorry if didnt explain this well. This is the auction client import java.io.*; import java.net.*; public class AuctionClient { private AuctionGui gui; private Socket socket; private DataInputStream dataIn; private DataOutputStream dataOut; //Auction Client constructor String name used as identifier for each client to allow server to pick the winning bidder public AuctionClient(String name,String server, int port) { gui = new AuctionGui("Bidomatic 5000"); gui.input.addKeyListener (new EnterListener(this,gui)); gui.addWindowListener(new ExitListener(this)); try { socket = new Socket(server, port); dataIn = new DataInputStream(socket.getInputStream()); dataOut = new DataOutputStream(socket.getOutputStream()); dataOut.writeUTF(name); while (true) { gui.output.append("\n"+dataIn.readUTF()); } } catch (Exception e) { e.printStackTrace(); } } public void sentBid(String bid) { try { dataOut.writeUTF(bid); } catch(IOException e) { e.printStackTrace(); } } public void disconnect() { try { socket.close(); } catch(IOException e) { e.printStackTrace(); } } public static void main (String args[]) throws IOException { if(args.length!=3) { throw new RuntimeException ("Syntax: java AuctionClient <name> <serverhost> <port>"); } int port = Integer.parseInt(args[2]); AuctionClient a = new AuctionClient(args[0],args[1],port); } } The Auction Server import java.io.*; import java.net.*; import java.util.*; public class AuctionServer { public AuctionServer(int port) throws IOException { ServerSocket server = new ServerSocket(port); while(true) { Socket client = server.accept(); DataInputStream in = new DataInputStream(client.getInputStream()); String name = in.readUTF(); System.out.println("New client "+name+" from " +client.getInetAddress()); BidHandler b = new BidHandler (name, client); b.start(); } } public static void main(String args[]) throws IOException { if(args.length != 1) throw new RuntimeException("Syntax: java AuctionServer <port>"); new AuctionServer(Integer.parseInt(args[0])); } } The BidHandler import java.net.*; import java.io.*; import java.util.*; import java.lang.Float; public class BidHandler extends Thread { Socket socket; DataInputStream in; DataOutputStream out; String name; float currentBid = 0.0f; AuctionItem paper = new AuctionItem(" News Paper ", " Free newspaper from 1990 ", 1.0f, false); protected static Vector handlers = new Vector(); public BidHandler(String name, Socket socket) throws IOException { this.name = name; this.socket = socket; in = new DataInputStream (new BufferedInputStream (socket.getInputStream())); out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream())); } public synchronized void run() { try { broadcast("New bidder has entered the room"); handlers.addElement(this); while(true) { broadcast(paper.getName() + paper.getDescription()+" for sale at: " +paper.getPrice()); while(paper.getStatus() == false) { String message = in.readUTF(); currentBid = Float.parseFloat(message); broadcast("Bidder entered " +currentBid); if(currentBid > paper.getPrice()) { paper.setPrice(currentBid); broadcast("New Higgest Bid is "+paper.getPrice()); } else if(currentBid < paper.getPrice()) { broadcast("Higgest Bid is "+paper.getPrice()); } else if(currentBid == paper.getPrice()) { broadcast("Higgest Bid is "+paper.getPrice()); } } } } catch(IOException ex) { System.out.println("-- Connection to user lost."); } finally { handlers.removeElement(this); broadcast(name+" left"); try { socket.close(); } catch(IOException ex) { System.out.println("-- Socket to user already closed ?"); } } } protected static void broadcast (String message) { synchronized(handlers) { Enumeration e = handlers.elements(); while(e.hasMoreElements()) { BidHandler handler = (BidHandler) e.nextElement(); try { handler.out.writeUTF(message); handler.out.flush(); } catch(IOException ex) { handler = null; } } } } } The AuctionItem Class class AuctionItem { String itemName; String itemDescription; float itemPrice; boolean itemStatus; //Create a new auction item with name, description, price and status public AuctionItem(String name, String description, float price, boolean status) { itemName = name; itemDescription = description; itemPrice = price; itemStatus = status; } //return the price of the item. public synchronized float getPrice() { return itemPrice; } //Set the price of the item. public synchronized void setPrice(float newPrice) { itemPrice = newPrice; } //Get the status of the item public synchronized boolean getStatus() { return itemStatus; } //Set the status of the item public synchronized void setStatus(boolean newStatus) { itemStatus = newStatus; } //Get the name of the item public String getName() { return itemName; } //Get the description of the item public String getDescription() { return itemDescription; } } There is also simple GUI to go with this that seems to be working fine. If anyone wants it will include the GUI code.

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• Data table multiple row selection

  - by Hari kanna

  i am a small time web develper i am working on JSF project i am a front end designer and also interested in JSF i try 2 solve this issue in web app... k my question is here... i have a datatable with checkbox i want 2 select multiple row selection with css background color....

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• C: getopt with list of acceptable optarg. What is the best practise ?

  - by Xavier Maillard

  Hi, I am writing a C program which is a frontend to a myriad tools. This fronted will be launched like this: my-frontend --action <AN ACTION> As all the tools have the same prefix, let say for this example this prefix is "foo". I want to concatenate "AN ACTION" to this prefix and exec this (if the tool exists). I have written something but my implementation uses strcmp to test that "AN ACTION" is a valid action. Even if this works, I do not like it. So I am looking for a nicer solution that would do the same. The list of possibilities is pretty small (less than 10) and static (the list is "hardcoded") but I am sure there is a more "C-ish" way to do this (using a struct or something like that). As I am not a C expert, I am asking for your help. Regards

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• Exposing some live data on a website - New to ASP.NET, need guidelines

  - by Carlos

  I have a large .NET based system running within the company intranet, which allows winforms users to see some live calculated numbers and a custom winforms control drawn live (but not real-time). The Forms users can also affect the operation of the system. I would like to just show the live numbers on a website, along with the custom control. Nothing needs to come back from the web user, as the web app is meant to be just for monitoring. All the numbers can be calculated at the server. It's been a long time since I touched ASP.NET, and I need to know how to proceed. What are the steps in building and deploying such a website? Any caveats I need to look out for?

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• get data from asp page

  - by sam

  I am wondering if there is anyway to grab the html that is generated from an ASP page. I am trying to pull a table from the page, and I foolishly used a static html page so I would not have to be constantly querying the server where this page resides while I tested out my code. The javascript code I wrote to grab to unlabeled table from the page works. Then when I put it into practice with the real page and found that the ASP page does not generate a viewable page with a jquery .get request on the URL. Is there any way to query the page for the table I need so that the ASP page returns a valid page on request? (I am also limited to using javascript and perl for this, the server where this will reside will not run php and I have no desire to learn ASP.NET to solve this by adding to the issue of proprietary software)

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• How to bind a complex dictionary to a Gridview in asp.net?

  - by Mehdi

  I've used an early binding of a dictionary<string, string> to a gridview to show Urls Text and its HRef as key-value and it works like a charm. But since I want to replace the dictionary with this one : dictionary<string, LinkInfo> the binding goes wrong! Should I handle some events like as onItemDataBound or something? and the LinkInfo structure is: public struct LinkInfo{ public string href; public bool Enabled; }

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• Cakephp, Retreive Data for HABTM Models using find

  - by user298079

  I am new to cakephp and I'm trying to accomplish something that should be relatively easy. I have 2 models projects & categories bind by HABTM relationship. I am trying to perform the following query - find all projects that belong to a category $projects = $this->Project->find('all', array('conditions' => array('Category.slug' => $category))); However when I'm doing so it generates an SQL error: SQL Error: 1054: Unknown column 'Category.slug' in 'where clause' What am I doing wrong??

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• Insert Stored Procedure, Using Asp.Net WebForm to Insert new [Customer]

  - by user2953815

  Can someone please help me create a stored procedure to insert a new customer from a web form. I am having difficulty making the state a drop down list for customer to pick a state from the list and having that inserted into the database. INSERT INTO Customer ( Cust_First, Cust_Middle, Cust_Last, Cust_Phone, Cust_Alt_Phone, Cust_Email, Add_Line1, Add_Line2, Add_Bill_Line1, Add_Bill_Line2, City, State_Prov_Name, Postal_Zip_Code, Country_ID ) VALUES ( @Cust_First, @Cust_Middle, @Cust_Last, @Cust_Phone, @Cust_Alt_Phone, @Cust_Email, @Add_Line1, @Add_Line2, @Add_Bill_Line1, @Add_Bill_Line2, @City, @State_Prov_Name, @Postal_Zip_Code, @Country_ID )"> <InsertParameters> <asp:Parameter Name="Cust_First" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_Middle" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_Last" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_Phone" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_Alt_Phone" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_Email" Type="String"></asp:Parameter> <asp:Parameter Name="Add_Line1" Type="String"></asp:Parameter> <asp:Parameter Name="Add_Line2" Type="String"></asp:Parameter> <asp:Parameter Name="Add_Bill_Line1" Type="String"></asp:Parameter> <asp:Parameter Name="Add_Bill_Line2" Type="String"></asp:Parameter> <asp:Parameter Name="City" Type="String"></asp:Parameter> <asp:Parameter Name="Postal_Zip_Code" Type="String"></asp:Parameter> <asp:Parameter Name="Cust_ID" Type="Int32"></asp:Parameter> <asp:Parameter Name="State_Prov_Name" Type="String"></asp:Parameter> <asp:Parameter Name="Country_Name" Type="String"></asp:Parameter> </InsertParameters>

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• String or binary data would be truncated -- Heisenberg problem

  - by harpo

  When you get this error, the first thing you ask is, which column? Unfortunately, SQL Server is no help here. So you start doing trial and error. Well, right now I have a statement like: INSERT tbl (A, B, C, D, E, F, G) SELECT A, B * 2, C, D, E, q.F, G FROM tbl ,othertable q WHERE etc etc Note that Some values are modified or linked in from another table, but most values are coming from the original table, so they can't really cause truncation going back to the same field (that I know of). Eliminating fields one at a time eventually makes the error go away, if I do it cumulatively, but — and here's the kicker — it doesn't matter which fields I eliminate. It's as if SQL Server is objecting to the total length of the row, which I doubt, since there are only about 40 fields in all, and nothing large. Anyone ever seen this before? Thanks. UPDATE: I have also done "horizontal" testing, by filtering out the SELECT, with much the same result. In other words, if I say WHERE id BETWEEN 1 AND 100: Error WHERE id BETWEEN 1 AND 50: No error WHERE id BETWEEN 50 AND 100: No error I tried many combinations, and it cannot be limited to a single row.

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• Unable to get data from a WCF client

  - by Scott

  I am developing a DLL that will provide sychronized time stamps to multiple applications running on the same machine. The timestamps are altered in a thread that uses a high performance timer and a scalar to provide the appearance of moving faster than real-time. For obvious reasons I want only 1 instance of this time library, and I thought I could use WCF for the other processes to connect to this and poll for timestamps whenever they want. When I connect however I never get a valid time stamp, just an empty DateTime. I should point out that the library does work. The original implementation was a single DLL that each application incorporated and each one was synced using windows messages. I'm fairly sure it has something to do with how I'm setting up the WCF stuff, to which I am still pretty new. Here are the contract definitions: public interface ITimerCallbacks { [OperationContract(IsOneWay = true)] void TimerElapsed(String id); } [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(ITimerCallbacks))] public interface ISimTime { [OperationContract] DateTime GetTime(); } Here is my class definition: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] public class SimTimeServer: ISimTime The host setup: // set up WCF interprocess comms host = new ServiceHost(typeof(SimTimeServer), new Uri[] { new Uri("net.pipe://localhost") }); host.AddServiceEndpoint(typeof(ISimTime), new NetNamedPipeBinding(), "SimTime"); host.Open(); and the implementation of the interface function server-side: public DateTime GetTime() { if (ThreadMutex.WaitOne(20)) { RetTime = CurrentTime; ThreadMutex.ReleaseMutex(); } return RetTime; } Lastly the client-side implementation: Callbacks myCallbacks = new Callbacks(); DuplexChannelFactory pipeFactory = new DuplexChannelFactory(myCallbacks, new NetNamedPipeBinding(), new EndpointAddress("net.pipe://localhost/SimTime")); ISimTime pipeProxy = pipeFactory.CreateChannel(); while (true) { string str = Console.ReadLine(); if (str.ToLower().Contains("get")) Console.WriteLine(pipeProxy.GetTime().ToString()); else if (str.ToLower().Contains("exit")) break; }

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• reRendering is not happening in jsf using data table

  - by palakolanusrinu

  HI, Rerendering is not working in my code please help in this <rich:dataTable id="bookIncome" value="#{myBean.ftBoookIncomelst}" var="item" rowKeyVar="row" first="0" width="100%"> <rich:subTable id="subBookIncome"value="#{item.txIncome}" var="income" rowKeyVar="row"> <rich:column id="descrtiptionColumn" width="30%"> <h:outputText value="#{income.descriptionCell.value}" rendered="#{!item.editableRow}" style="#{income.descriptionCell.boldClass}"> </h:outputText> <rich:inplaceInput layout="block" value="#{income.descriptionCell.value}" required="true" rendered="#{item.editableRow}" requiredMessage="Description at row #{row+1} wasn't filled." changedHoverClass="hover" viewHoverClass="hover" viewClass="inplace" changedClass="inplace" selectOnEdit="true" editEvent="onclick"> </rich:inplaceInput> In the above code i have proper id for datatable and i'm calling my ajax call using But its not showing any response but its hitting the server and its calling proper method and updating the required list also..Please help in this why its not rendering its not showing any exception on console also...

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• how to define a structural type that refers to itself?

  - by IttayD

  I want to create a method sum that I can call on different types, specifically sum(1,2). def sum[A](a1: A, a2: A) = a1 + a2 This fails because the compiler can't tell if A has a method '+' I tried to define a structural type: type Addable = {def +(a: Addable)} This fails because of an illegal cyclic reference How can I achieve this in a type safe way without requiring A to extend a specific trait?

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• Circular buffer in JavaScript

  - by lonforce

  I was wondering whether anyone has already implemented a circular buffer in JavaScript? How would you do that without having pointers?

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• Modifying C# dictionary value

  - by minjang

  I'm a C++ expert, but not at all for C#. I created a Dictionary<string, STATS>, where STATS is a simple struct. Once I built the dictionary with initial string and STATS pairs, I want to modify the dictionary's STATS value. In C++, it's very clear: Dictionary<string, STATS*> benchmarks; Initialize it... STATS* stats = benchmarks[item.Key]; // Touch stats directly However, I tried like this in C#: Dictionary<string, STATS> benchmarks = new Dictionary<string, STATS>(); // Initialize benchmarks with a bunch of STATS foreach (var item in _data) benchmarks.Add(item.app_name, item); foreach (KeyValuePair<string, STATS> item in benchmarks) { // I want to modify STATS value inside of benchmarks dictionary. STATS stat_item = benchmarks[item.Key]; ParseOutputFile("foo", ref stat_item); // But, not modified in benchmarks... stat_item is just a copy. } This is a really novice problem, but wasn't easy to find an answer. EDIT: I also tried like the following: STATS stat_item = benchmarks[item.Key]; ParseOutputFile(file_name, ref stat_item); benchmarks[item.Key] = stat_item; However, I got the exception since such action invalidates Dictionary: Unhandled Exception: System.InvalidOperationException: Collection was modified; enumeration operation may not execute. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext() at helper.Program.Main(String[] args) in D:\dev\\helper\Program.cs:line 75

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• Group MySQL Data into Arbitrarily Sized Time Buckets

  - by Eric J.

  How do I count the number of records in a MySQL table based on a timestamp column per unit of time where the unit of time is arbitrary? Specifically, I want to count how many record's timestamps fell into 15 minute buckets during a given interval. I understand how to do this in buckets of 1 second, 1 minute, 1 hour, 1 day etc. using MySQL date functions, e.g. SELECT YEAR(datefield) Y, MONTH(datefield) M, DAY(datefield) D, COUNT(*) Cnt FROM mytable GROUP BY YEAR(datefield), MONTH(datefield), DAY(datefield) but how can I group by 15 minute buckets?

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• hibernate not throwing stale state exception nor it is overwriting data

  - by Reddy

  Our application do the following. 1. Start the transaction. 2. Execute a query using prepared statement 3. Check a condition to see the number of rows updated are equal to the required number. 4. It commits on success of above condition otherwise it will roll back However the problem is that when two threads are simultaneously enter this code. Thread-1 is updating a row in step 2. It checked the condition and committed successfully since the condition is successful. Thread-2 started execution somewhere between steps 1 & 4, and it is failing on at condition checking at step 3 (as it is getting number of updated rows as 0). I expected second thread to throw an exception but it is not. What could be the problem?

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• Fastest way to represent a collection of bits in PHP?

  - by Piskvor

  What is a good way to represent a collection of bits? I have a set of various on/off toggles (thousands of them) and need to store and retrieve their state. The naïve implementation would be an array of booleans, but I'm wondering if there's a better way (better in terms of access speed and/or memory requirements). I've found this BitArray implementation, but it's limited to 32 bits, which is not enough for this case.

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• advanced python autovivification

  - by Zhang18

  This question is about implementing the full PERL autovivification in python. I know similary questions were asked before and so far the best answre is http://stackoverflow.com/questions/635483/what-is-the-best-way-to-implement-nested-dictionaries-in-python/652284#652284. However, I'm looking to do this: a['x']['y'].append('z') without declaring a['x']['y'] = [] first, or rather, not declaring a['x'] = {} either. I know dict and list classes sorta don't mix so this is hard, but I'm interested in seeing if someone has an ingenius solution probably involving creating an inherited class from dict but defined a new append method on it? I also know this might throw off some python purists who will ask me to stick with Perl. But even just for a challenge, I'd like to see something. thx!

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• list or container O(1)-ish insertion/deletion performance, with array semantics

  - by Chris Kaminski

  I'm looking for a collection that offers list semantics, but also allows array semantics. Say I have a list with the following items: apple orange carrot pear then my container array would: container[0] == apple container[1] == orangle container[2] == carrot Then say I delete the orange element: container[0] == apple container[1] == carrot I don't particularly care if sort order is maintained, I'd just like the array values to function as accelerators to the list items, and I want to collapse gaps in the array without having to do an explicit resizing.

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• java: copy-on-write data structure?

  - by Jason S

  Is there anything in Java that implements something like the following interface MSet<T> extends Iterable<T> { /** * return a new set which consists of this set plus a new element. * This set is not changed. */ MSet<T> add(T t); /** * return a new set which consists of this set minus a designated element. * This set is not changed. */ MSet<T> remove(T t); }

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• Generic version control strategy for select table data within a heavily normalized database

  - by leppie

  Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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