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• Selecting one object from a one-to-many relationship in Hibernate

  - by Nick Thomson

  I have two tables: Job job_id, <other data> Job_Link job_link_id, job_id, start_timestamp, end_timestamp, <other data> There may be multiple records in Job_Link specifying the same job_id with the start_timestamp and end_timestamps to indicate when those records are considered "current", it is guaranteed that start_timestamp and end_timestamp will not overlap. We have entities for both the Job and Job_Link tables and defining a one-to-many relationship to load all the job_links wouldn't be a problem. However we'd like to avoid that and have a single job_link item in the Job entity that will contain only the "current" Job_Link object. Is there any way to achive that?

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• Ruby on Rails: create records for multiple models with one form and one submit

  - by notblakeshelton

  I have a 3 models: quote, customer, and item. Each quote has one customer and one item. I would like to create a new quote, a new customer, and a new item in their respective tables when I press the submit button. I have looked at other questions and railscasts and either they don't work for my situation or I don't know how to implement them. I also want my index page to be the page where I can create everything. quote.rb class Quote < ActiveRecord::Base attr_accessible :quote_number has_one :customer has_one :item end customer.rb class Customer < ActiveRecord::Base #unsure of what to put here #a customer can have multiple quotes, so would i use: has_many :quotes #<----? end item.rb class Item < ActiveRecord::Base #also unsure about this #each item can also be in multiple quotes quotes_controller.rb class QuotesController < ApplicationController def index @quote = Quote.new @customer = Customer.new @item = item.new end def create @quote = Quote.new(params[:quote]) @quote.save @customer = Customer.new(params[:customer]) @customer.save @item = Item.new(params[:item]) @item.save end end items_controller.rb class ItemsController < ApplicationController def index end def new @item = Item.new end def create @item = Item.new(params[:item]) @item.save end end customers_controller.rb class CustomersController < ApplicationController def index end def new @customer = Customer.new end def create @customer = Customer.new(params[:customer]) @customer.save end end quotes/index.html.erb <%= form_for @quote do |f| %> <%= f.fields_for @customer do |builder| %> <%= label_tag :firstname %> <%= builder.text_field :firstname %> <%= label_tag :lastname %> <%= builder.text_field :lastname %> <% end %> <%= f.fields_for @item do |builder| %> <%= label_tag :name %> <%= builder.text_field :name %> <%= label_tag :description %> <%= builder.text_field :description %> <% end %> <%= label_tag :quote_number %> <%= f.text_field :quote_number %> <%= f.submit %> <% end %> When I try submitting that I get an error: Can't mass-assign protected attributes: item, customer So to try and fix it I updated the attr_accessible in quote.rb to include :item, :customer but then I get this error: Item(#) expected, got ActiveSupport::HashWithIndifferentAccess(#) Any help would be greatly appreciated.

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• ROOT_MISMATCH error after following FAQ directions

  - by Adko

  While using Ubuntu One in 11.04 I am unable to change my account info. When I made the switch to 11.04 I forgot that I already had an Ubuntu One account so, I made a new one. However, upon going through one of my email accounts I found my old Ubuntu One login information. I then attempted to switch the account associated with my desktop to my first email. Now, despite following the directions found at https://wiki.ubuntu.com/UbuntuOne/FAQ/WhatToDoWhenSyncdaemonSaysRootMismatch I continue to get the error "File sync error. (local and server roots are different (ROOT_MISMATCH))". Any help would be appreciated.

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• Does a mini PCIe SSD fit into a Acer Aspire One?

  - by Narcolapser

  Question: What, if any, mini PCIe SSDs fit into the mini PCIe slot of the Acer Aspire one AOD250? Info: I have an Aspire One and I've been considering loading it with an SSD. The mini PCIe drives fascinate me and so I want to try that approach. Also they tend to be cheaper and not much slower. (at least not on Read time which matters more for a netbook) But I've heard that some times computers don't support certain mini PCIe cards. And I was wondering if anyone knew about the Aspire One? I tried asking Acer tech support, but they didn't know jack and spent the whole time informing that I would have to support my Ubuntu install on my own, which I was. Anyway. Rant Aside, I'm looking at this drive: http://www.newegg.com/Product/Product.aspx?Item=N82E16820183252 It states it is exclusively for the Eee PC. now does that mean It was designed for the Eee PC but will work in my netbook. or is something going to go wrong? (like right now my concern is it physically not fitting.) Any information would be appreciated. o7

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• how to get the result query one by one in jsp and mysql

  - by user261002

  I am trying to implement as Online Mock exam in JSP, but I have a problem to get the questions one by one, it get connceted for the first time, and show me the first question and answers, but when I click on "next" again, it still show me the first question, I think by clicking on "next" it start querying again. please help me. this is my bean : database.SQLSelectStatement sqlselect; database.SQLSelectStatement sqlselect2; static ResultSet questions; static ResultSetMetaData rsm; static ResultSet answers; public void setConnection() throws SQLException { if (database.DatabaseManager.getInstance().connectionOK()) { sqlselect = new database.SQLSelectStatement("question", "question", "0"); sqlselect2 = new database.SQLSelectStatement("answers", "question_id", "0"); questions = sqlselect.executeWithNoCondition(); } } public int i=0; public String getQuestions() throws SQLException { String result = ""; rsm = questions.getMetaData(); for (int i = 0; i < rsm.getColumnCount(); i++) { result += "<th>" + rsm.getColumnName(i + 1) + "</th>"; } if (!questions.isLast()) { questions.next(); System.out.println(i+1); result += "<tr>"; result += "<td>" + questions.getInt(1) + "</td>"; result += "<td>" + questions.getString(2) + "</td>"; result += "</tr>"; result += "<tr>"; sqlselect2.setValue(String.valueOf(questions.getInt(1))); answers = sqlselect2.Execute(); while (answers.next()) { result += "<tr> <td colspan='2'><input type='radio' name='answer' value='" + answers.getString(2) + "'> " + answers.getString(2) + "</td></tr>"; } result += "</tr>"; answers.close(); } return result; } this is the HTML: <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>JSP Page</title> </head> <body> <h1>JSP Page</h1> <jsp:useBean id="exam" class="exam.ExamQuestions"></jsp:useBean> <% exam.setConnection(); %> <form method="post"> <table > <%=exam.getQuestions()%> </table> <input type="submit" name="action" value="next"/> </form> <% String action = request.getParameter("action"); if ("next".equals(action)) { out.println(request.getParameter("answer")); } %> </body> </html>

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• Does HashMap provide a one to one correspondence?

  - by Roman

  I found the following statement: Map is an object that stores key/volume pairs. Given a key, you can find its value. Keys must be unique, but values may be duplicated. For example I have just one key/value pair (3,4). And now I put a new pair (3,5). It will remove the old pair. Right? But if I put (2,4) instead of (3,4) I will add a new pair of key/value to the HashMap. Right?

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• PHP/MySQL - Working with two databases, one shared and one local to an instance of application

  - by Extrakun

  The situation: Using a off-the-shelf PHP application, I have to add in a new module for extra functionality. Today, it is made known that eventually four different instances of the application are to be deployed, but the data from the new functionality is to be shared among those 4 instances. Each instance should still have their own database for users, content and etc. So the data for the new functionality goes into a 'shared' database. The data for the application (user login, content, uploads) go into a 'local' database To make things more complex, the new module I am writing will fetch data from the local DB and the shared DB at the same time. A re-write of the base application will take too long. I only have control over the new module which I am writing. The ideal solution: Is there a way to encapsulate 2 databases into one name using MySQL? I do not wish to switch DB connections or specifically name the DB to query from inside my SQL statements. The application uses a DB wrapper, so I am able to change it somehow so I can invisibly attempt to read/write to two different DB. What is the best way to handle this problem?

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• Multiplying two matrices from two text files with unknown dimensions

  - by wes schwertner

  This is my first post here. I've been working on this c++ question for a while now and have gotten nowhere. Maybe you guys can give me some hints to get me started. My program has to read two .txt files each containing one matrix. Then it has to multiply them and output it to another .txt file. My confusion here though is how the .txt files are setup and how to get the dimensions. Here is an example of matrix 1.txt. #ivalue #jvalue value 1 1 1.0 2 2 1 The dimension of the matrix is 2x2. 1.0 0 0 1 Before I can start multiplying these matrices I need to get the i and j value from the text file. The only way I have found out to do this is int main() { ifstream file("a.txt"); int numcol; float col; for(int x=0; x<3;x++) { file>>col; cout<<col; if(x==1) //grabs the number of columns numcol=col; } cout<<numcol; } The problem is I don't know how to get to the second line to read the number of rows. And on top of that I don't think this will give me accurate results for other matrices files. Let me know if anything is unclear. UPDATE Thanks! I got getline to work correctly. But now I am running into another problem. In matrix B it is setup like: #ivalue #jvalue Value 1 1 0.1 1 2 0.2 2 1 0.3 2 2 0.4 I need to let the program know that it needs to go down 4 lines, maybe even more (The matrices dimensions are unknown. My matrix B example is a 2x2, but it could be a 20x20). I have a while(!file.eof()) loop my program to let it loop until the end of file. I know I need a dynamic array for multiplying, but would I need one here also? #include <iostream> #include <fstream> using namespace std; int main() { ifstream file("a.txt"); //reads matrix A while(!file.eof()) { int temp; int numcol; string numrow; float row; float col; for(int x=0; x<3;x++) { file>>col; if(x==1) { numcol=col; //number of columns } } string test; getline(file, test); //next line to get rows for(int x=0; x<3; x++) { file>>test; if(x==1) { numrow=test; //sets number of rows } } cout<<numrow; cout<<numcol<<endl; } ifstream file1("b.txt"); //reads matrix 2 while(!file1.eof()) { int temp1; int numcol1; string numrow1; float row1; float col1; for(int x=0; x<2;x++) { file1>>col1; if(x==1) numcol1=col1; //sets number of columns } string test1; getline(file1, test1); //In matrix B there are four rows. getline(file1, test1); //These getlines go down a row. getline(file1, test1); //Need help here. for(int x=0; x<2; x++) { file1>>test1; if(x==1) numrow1=test1; } cout<<numrow1; cout<<numcol1<<endl; } }

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• C++: Most common way to talk to one application from the other one

  - by MInner

  In bare outlines, I've got an application which looks through the directories at startup and creates special files' index - after that it works like daemon. The other application creates such 'special' files and places them in some directory. What way of informing the first application about a new file (to index it) is the most common, simple (the first one is run-time, so it shouldn't slow it too much), and cross-platform if it is possible? I've looked through RPC and IPC but they are too heavy (also non-cross-platform and slow (need a lot of features to work - I need a simple light well-working way), probably).

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• Cannot run a VM with more than three network interfaces with KVM

  - by Bostonvaulter

  I'm running KVM on top of Ubuntu 10.10 Server I can create VM's (Virtual Machine) and network interfaces fine but I cannot seem to add more than three network interfaces. As soon as I have a VM with four network interfaces it gets stuck on startup at the starting SeaBIOS page with this message: Starting SeaBIOS (version pre-0.6.1-20100702_143500-palmer) So far I've verified this with two VM's, a Ubuntu 10.10 desktop and a Vyatta router. The specific network hardware I assign to the VM's doesn't seem to matter. I'm trying to have one bridged interface and three private networks using Vyatta to route between them. Does anyone know why I can't run a VM with more than three network interfaces? Edit: Additionally the KVM thread responsible for the specific VM hangs using ~100% CPU (i.e. one core). Here's the command for the process that is hanging: /usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 512 -smp 1,sockets=1,cores=1,threads=1 -name vyatta -uuid 6dff7c94-6810-423e-5fea-fec10da0e9b7 -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/vyatta.monitor,server,nowait -mon chardev=monitor,mode=readline -rtc base=utc -boot c -drive file=/home/rams/virtual-machines/vyatta.img,if=none,id=drive-ide0-0-0,boot=on,format=raw -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -device rtl8139,vlan=0,id=net0,mac=00:54:00:be:cc:4b,bus=pci.0,addr=0x3 -net tap,fd=97,vlan=0,name=hostnet0 -device rtl8139,vlan=1,id=net1,mac=52:54:00:da:59:ed,bus=pci.0,addr=0x5 -net tap,fd=98,vlan=1,name=hostnet1 -device rtl8139,vlan=2,id=net2,mac=52:54:00:ce:22:b6,bus=pci.0,addr=0x6 -net tap,fd=99,vlan=2,name=hostnet2 -device rtl8139,vlan=3,id=net3,mac=52:54:00:1e:bc:46,bus=pci.0,addr=0x7 -net tap,fd=101,vlan=3,name=hostnet3 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -vnc 127.0.0.1:0 -k en-us -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 Edit: I've also found an error in dmesg that might be related (it also shows up when running virtd in verbose mode): 14:47:24.399: warning : qemudParsePCIDeviceStrs:1422 : Unexpected exit status '1', qemu probably failed I've also tried disabling app armor but that doesn't seem to make a difference.

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• Are Motherboards for the Acer Aspire One AOA150 Netbook Compatible with the AOA110?

  - by Mindstormscreator

  I have an Acer Aspire One ZG5 AOA110-1588 netbook, and the motherboard doesn't have a port for a SATA 2.5 inch hard drive; it only supports this slow 8GB SSD type drive. Through research I've discovered that the AOA150 motherboards do have a SATA slot, and the bottom plate of these laptops have an appropriate protrusion for the drive to fit in (for example, compare this to this). The AOA110 and AOA150 models are very similar in appearance and specs. I've even seen tutorials that involve soldering a SATA connector onto the AOA110's motherboard, essentially creating an AOA150 motherboard (right?) So, could I just swap out the motherboard in my netbook with the MBS0506001? (I'd post another link to the actual board but can't because of the spam prevention...) I assume I would also need to purchase and replace the bottom cover with a larger one and possibly get a hard drive caddy as well...? Thanks!

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• UPS recommendations for three grey boxes?

  - by Margaret

  Hey all We have a series of grey-box style computers acting as servers at my workplace (rather than rack-mount). We were looking to get Uninterruptible Power Supplies for them. However, I'm not sure how many at what capacity are required. I'd assume it would be a good idea to hook the peripherals in as well - there's a 18.5" LCD monitor with a KVM, along with a couple of USB hard drives that require power. I currently have the most vital machine hooked up to a cheap (temporary) UPS, but it's probably close to worse than nothing. I'm looking for reasonable value for money, though I can probably negotiate with my boss on price range. I recognise that I may well need to buy two (or even three) UPSs to support the three machines. Any recommendations?

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• How to connect to a PEAP GTC wifi network with Android 2.2 on a nexus one?

  - by Glen

  Hi, I recently updated my nexus one to 2.2. Now I can't connect to my uni's wifi. They use PEAP with GTC. I had it working fine on 2.1. Also it works fine on my Ubuntu laptop. I have entered my uni number (user name) in the identity box. I have entered my password in the password box. I have emailed the certificated that works on Ubuntu to my self and installed it on the nexus one. I have enabled secure credentials. What am I doing wrong? Thanks, Glen.

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• Windows 8.1 touchpad three-finger-multitouch gesture gone

  - by THEVAN3D

  Couple of days ago, i installed the Windows 8.1 Pro WMC and all of a sudden the touchpad gesture, which worked like a charm back in Win 8.1 preview, Win 8 and even Win 7, just stopped working. I am talking about the "Three Finger Flick" feature, which is used to go back and forward in folders and/or internet browsers at first i didnt even have the left edge pull feature, but then i added some values in this key into regedit, and now i have it [HKEY_CURRENT_USER\Software\Synaptics\SynTPEnh\ZoneConfig\TouchPadPS2\Left Edge Pull] I Googled that, i didnt know what to do by myself and i dont know where to write and what to write anything in order to get the three finger flick back too I installed various versions of drivers starting from about version 15 to the version 17.0.8.0 (the one that i currently have), and even though i have all the other gestures, taps and swipes working they are not in the device settings, there is no multitouch gestures in device settings so thats why i guess i have to write something in regedit, but again, i dont know what to write, and where to write. please help me if you can

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• Windows 7: from Geforce 8800 to three monitors?

  - by lance

  I've got a GeForce 8800 that I've quite happy with. It drives my two 23" widescreen displays well. Now I've got a 19" standard display that I want to stick between the two widescreens. My second PCIe 16x slot is unused (as is the PCI slot below that), and I want to add a card to my Win7 x64 system. This 19" display won't be used for gaming, so I don't need anything fancy. Here are two cards I was considering, but I'm wondering if they're bad choices for some reason? If they're both fine choices, which is better and why? Again, I'm needing to power only the 19" standard display with this card, and it won't play games. I just need 1280x1024 in Win7 x64. NVidia: Galaxy 95TFE8HUFEXX GeForce 9500 GT Video Card - 512MB DDR2, PCI Express 2.0 ATI: ASUS EAH4350 SILENT/DI/51 Radeon HD 4350 Video Card - 512MB DDR2, PCI Express 2.0

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• Cloud storage services offering one-time download links? [closed]

  - by TARehman

  Is anyone aware of consumer-targeted cloud storage services that allow users to generate a one-time download link for hosted files? Case in point: I have an encrypted container with some documents I need to send to a vendor. I would prefer to give them a one-time download link, so that I know when they have accessed the file, and then inform them of the passphrase by phone. I have heard that MediaFire offers 1-time links, but that they are buried in tons of advertising. At the moment, I'm not sure that I consider MediaFire fully legitimate; I'm more interested in solutions with Google Drive, Box.net, DropBox, etc.

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• how to pass one variable value frm one class to the oder

  - by Arunabha

  i hav two packages one is com.firstBooks.series.db.parser which hav a java file XMLParser.java,i hav another package com.firstBooks.series79 which hav a class called AppMain.NW i want to send the value of a variable called _xmlFileName frm AppMain class to the xmlFile variable in XMLParser class,i am posting the codes for both the class,kindly help me. package com.firstBooks.series.db.parser; import java.io.IOException; import java.io.InputStream; import java.util.Vector; import net.rim.device.api.xml.parsers.DocumentBuilder; import net.rim.device.api.xml.parsers.DocumentBuilderFactory; import net.rim.device.api.xml.parsers.ParserConfigurationException; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.NodeList; import org.xml.sax.SAXException; import com.firstBooks.series.db.Question; public class XMLParser { private Document document; public static Vector questionList; public static String xmlFile; public XMLParser() { questionList = new Vector(); } public void parseXMl() throws SAXException, IOException, ParserConfigurationException { // Build a document based on the XML file. DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); InputStream inputStream = getClass().getResourceAsStream(xmlFile); document = builder.parse(inputStream); } public void parseDocument() { Element element = document.getDocumentElement(); NodeList nl = element.getElementsByTagName("question"); if (nl != null && nl.getLength() > 0) { for (int i = 0; i < nl.getLength(); i++) { Element ele = (Element) nl.item(i); Question question = getQuestions(ele); questionList.addElement(question); } } } private Question getQuestions(Element element) { String title = getTextValue(element, "title"); String choice1 = getTextValue(element, "choice1"); String choice2 = getTextValue(element, "choice2"); String choice3 = getTextValue(element, "choice3"); String choice4 = getTextValue(element, "choice4"); String answer = getTextValue(element, "answer"); String rationale = getTextValue(element, "rationale"); Question Questions = new Question(title, choice1, choice2, choice3, choice4, answer, rationale); return Questions; } private String getTextValue(Element ele, String tagName) { String textVal = null; NodeList nl = ele.getElementsByTagName(tagName); if (nl != null && nl.getLength() > 0) { Element el = (Element) nl.item(0); textVal = el.getFirstChild().getNodeValue(); } return textVal; } } Nw the code for AppMain class //#preprocess package com.firstBooks.series79; import net.rim.device.api.ui.UiApplication; import com.firstBooks.series.ui.screens.HomeScreen; public class AppMain extends UiApplication { public static String _xmlFileName; public static boolean _Lite; public static int _totalNumofQuestions; public static void initialize(){ //#ifndef FULL /* //#endif _xmlFileName = "/res/Series79_FULL.xml"; _totalNumofQuestions = 50; _Lite = false; //#ifndef FULL */ //#endif //#ifndef LITE /* //#endif _xmlFileName = "/res/Series79_LITE.xml"; _totalNumofQuestions = 10; _Lite = true; //#ifndef LITE */ //#endif } private AppMain() { initialize(); pushScreen(new HomeScreen()); } public static void main(String args[]) { new AppMain().enterEventDispatcher(); } }

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• XSLT, process elements one by one

  - by qui

  Hi I am quite weak at XSLT so this might seem obvious. Here is some sample XML <term> <name>cholecystocolonic fistula</name> <definition>blah blah</definition> <reference>cholecystocolostomy</reference> </term> And here is the XSLT I wrote a while ago to process it <xsl:template name="term"> { "dictitle": "<xsl:value-of select="name" disable-output-escaping="yes" />", "html": "<xsl:value-of select="definition" disable-output-escaping="yes"/>", "referece": "<xsl:value-of select="reference" disable-output-escaping="yes"/> } </xsl:template> Basically I am creating JSON from the XML. The requirements have now changed so that now the XML can have more than one definition tag and reference tag. They can appear in any order, i.e definition, reference, reference, definition, reference. How can I update the XSLT to accommodate this? Probably worth mentioning that because my XSLT processor is using .NET I can only use XSLT 1.0 commands. Many thanks!

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• using a texture mesh and wireframe mesh in threejs

  - by Andy Poes

  I'm trying to draw a wireframe mesh and a textured mesh in threeJS but when I have both added to my scene the textured mesh doesn't display. Code below: I'm having trouble creating two meshes that share the same geometry where one of the materials is wireframe and the other is a texture. If one of the materials is wireframe and the other is just a color fill it works fine- but as soon as I make the second material a texture it stops working. If I comment out scene.add( wireMesh ); then the textured mesh shows up. var wireMat = new THREE.MeshBasicMaterial( { color:0x00FFFF, wireframe: true, transparent: true, overdraw:true } ); var wireMesh = new THREE.Mesh(geometry, wireMat); scene.add( wireMesh ); var texture = texture = THREE.ImageUtils.loadTexture( 'textures/world.jpg' ); var imageMat = new THREE.MeshBasicMaterial( {color:0xffffff, map: texture } ); var fillMesh = new THREE.Mesh(geometry, imageMat); scene.add( fillMesh );

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• How to enable a two-finger drag on a mac in Silverlight?

  - by Edward Tanguay

  In a Silverlight 4 application I have a ScrollViewer which I enable the user to scroll with the mouse wheel by using SetIsMouseWheelScrollingEnabled(): <ScrollViewer x:Name="CodeBoxScrollViewerModelSingular" tk:DockPanel.Dock="Left" Style="{StaticResource ScrollViewerCodeBoxStyle}"> <TextBox Text="{Binding SingularModelFileContent}" Style="{StaticResource TextBoxCodeBoxStyle}"/> </ScrollViewer> CodeBoxScrollViewerModelSingular.SetIsMouseWheelScrollingEnabled(true); However, someone tested it on a Mac and said: The only problem I noticed on a quick test was that I couldn't scroll down by using a two-finger drag, which has been standard UI behavior on the Mac for several years now. Is there any way to enable a "two-finger drag" on the Mac as you can enable mouse wheel scrolling?

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• Bad resolution from Displayport converter on third of three screens

  - by Carl

  I am currently using three screens at the same time with my ATI 5770 & an active Displayport converter. The thing is that the third screen (the one using the active Displayport converter) is showing terrible resolution compared to my other two screens. The third screen is a Samsung Syncmaster P23. Two of my screens have a max resolution of 1920x1080, meanwhile the third on is only capable of 1600x1200. Do any of you know a solution to this problem?

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• BizTalk: History of one project architecture

  - by Leonid Ganeline

  "In the beginning God made heaven and earth. Then he started to integrate." At the very start was the requirement: integrate two working systems. Small digging up: It was one system. It was good but IT guys want to change it to the new one, much better, chipper, more flexible, and more progressive in technologies, more suitable for the future, for the faster world and hungry competitors. One thing. One small, little thing. We cannot turn off the old system (call it A, because it was the first), turn on the new one (call it B, because it is second but not the last one). The A has a hundreds users all across a country, they must study B. A still has a lot nice custom features, home-made features that cannot disappear. These features have to be moved to the B and it is a long process, months and months of redevelopment. So, the decision was simple. Let’s move not jump, let’s both systems working side-by-side several months. In this time we could teach the users and move all custom A’s special functionality to B. That automatically means both systems should work side-by-side all these months and use the same data. Data in A and B must be in sync. That’s how the integration projects get birth. Moreover, the specific of the user tasks requires the both systems must be in sync in real-time. Nightly synchronization is not working, absolutely.   First draft The first draft seems simple. Both systems keep data in SQL databases. When data changes, the Create, Update, Delete operations performed on the data, and the sync process could be started. The obvious decision is to use triggers on tables. When we are talking about data, we are talking about several entities. For example, Orders and Items [in Orders]. We decided to use the BizTalk Server to synchronize systems. Why it was chosen is another story. Second draft   Let’s take an example how it works in more details. 1.       User creates a new entity in the A system. This fires an insert trigger on the entity table. Trigger has to pass the message “Entity created”. This message includes all attributes of the new entity, but I focused on the Id of this entity in the A system. Notation for this message is id.A. System A sends id.A to the BizTalk Server. 2.       BizTalk transforms id.A to the format of the system B. This is easiest part and I will not focus on this kind of transformations in the following text. The message on the picture is still id.A but it is in slightly different format, that’s why it is changing in color. BizTalk sends id.A to the system B. 3.       The system B creates the entity on its side. But it uses different id-s for entities, these id-s are id.B. System B saves id.A+id.B. System B sends the message id.A+id.B back to the BizTalk. 4.       BizTalk sends the message id.A+id.B to the system A. 5.       System A saves id.A+id.B. Why both id-s should be saved on both systems? It was one of the next requirements. Users of both systems have to know the systems are in sync or not in sync. Users working with the entity on the system A can see the id.B and use it to switch to the system B and work there with the copy of the same entity. The decision was to store the pairs of entity id-s on both sides. If there is only one id, the entities are not in sync yet (for the Create operation). Third draft Next problem was the reliability of the synchronization. The synchronizing process can be interrupted on each step, when message goes through the wires. It can be communication problem, timeout, temporary shutdown one of the systems, the second system cannot be synchronized by some internal reason. There were several potential problems that prevented from enclosing the whole synchronization process in one transaction. Decision was to restart the whole sync process if it was not finished (in case of the error). For this purpose was created an additional service. Let’s call it the Resync service. We still keep the id pairs in both systems, but only for the fast access not for the synchronization process. For the synchronizing these id-s now are kept in one main place, in the Resync service database. The Resync service keeps record as: ·       Id.A ·       Id.B ·       Entity.Type ·       Operation (Create, Update, Delete) ·       IsSyncStarted (true/false) ·       IsSyncFinished (true/false0 The example now looks like: 1.       System A creates id.A. id.A is saved on the A. Id.A is sent to the BizTalk. 2.       BizTalk sends id.A to the Resync and to the B. id.A is saved on the Resync. 3.       System B creates id.B. id.A+id.B are saved on the B. id.A+id.B are sent to the BizTalk. 4.       BizTalk sends id.A+id.B to the Resync and to the A. id.A+id.B are saved on the Resync. 5.       id.A+id.B are saved on the B. Resync changes the IsSyncStarted and IsSyncFinished flags accordingly. The Resync service implements three main methods: ·       Save (id.A, Entity.Type, Operation) ·       Save (id.A, id.B, Entity.Type, Operation) ·       Resync () Two Save() are used to save id-s to the service storage. See in the above example, in 2 and 4 steps. What about the Resync()? It is the method that finishes the interrupted synchronization processes. If Save() is started by the trigger event, the Resync() is working as an independent process. It periodically scans the Resync storage to find out “unfinished” records. Then it restarts the synchronization processes. It tries to synchronize them several times then gives up.     One more thing, both systems A and B must tolerate duplicates of one synchronizing process. Say on the step 3 the system B was not able to send id.A+id.B back. The Resync service must restart the synchronization process that will send the id.A to B second time. In this case system B must just send back again also created id.A+id.B pair without errors. That means “tolerate duplicates”. Fourth draft Next draft was created only because of the aesthetics. As it always happens, aesthetics gave significant performance gain to the whole system. First was the stupid question. Why do we need this additional service with special database? Can we just master the BizTalk to do something like this Resync() does? So the Resync orchestration is doing the same thing as the Resync service. It is started by the Id.A and finished by the id.A+id.B message. The first works as a Start message, the second works as a Finish message.     Here is a diagram the whole process without errors. It is pretty straightforward. The Resync orchestration is waiting for the Finish message specific period of time then resubmits the Id.A message. It resubmits the Id.A message specific number of times then gives up and gets suspended. It can be resubmitted then it starts the whole process again: waiting [, resubmitting [, get suspended]], finishing. Tuning up The Resync orchestration resubmits the id.A message with special “Resubmitted” flag. The subscription filter on the Resync orchestration includes predicate as (Resubmit_Flag != “Resubmitted”). That means only the first Sync orchestration starts the Resync orchestration. Other Sync orchestration instantiated by the resubmitting can finish this Resync orchestration but cannot start another instance of the Resync   Here is a diagram where system B was inaccessible for some period of time. The Resync orchestration resubmitted the id.A two times. Then system B got the response the id.A+id.B and this finished the Resync service execution. What is interesting about this, there were submitted several identical id.A messages and only one id.A+id.B message. Because of this, the system B and the Resync must tolerate the duplicate messages. We also told about this requirement for the system B. Now the same requirement is for the Resunc. Let’s assume the system B was very slow in the first response and the Resync service had time to resubmit two id.A messages. System B responded not, as it was in previous case, with one id.A+id.B but with two id.A+id.B messages. First of them finished the Resync execution for the id.A. What about the second id.A+id.B? Where it goes? So, we have to add one more internal requirement. The whole solution must tolerate many identical id.A+id.B messages. It is easy task with the BizTalk. I added the “SinkExtraMessages” subscriber (orchestration with one receive shape), that just get these messages and do nothing. Real design Real architecture is much more complex and interesting. In reality each system can submit several id.A almost simultaneously and completely unordered. There are not only the “Create entity” operation but the Update and Delete operations. And these operations relate each other. Say the Update operation after Delete means not the same as Update after Create. In reality there are entities related each other. Say the Order and Order Items. Change on one of it could start the series of the operations on another. Moreover, the system internals are the “black boxes” and we cannot predict the exact content and order of the operation series. It worth to say, I had to spend a time to manage the zombie message problems. The zombies are still here, but this is not a problem now. And this is another story. What is interesting in the last design? One orchestration works to help another to be more reliable. Why two orchestration design is more reliable, isn’t it something strange? The Synch orchestration takes all the message exchange between systems, here is the area where most of the errors could happen. The Resync orchestration sends and receives messages only within the BizTalk server. Is there another design? Sure. All Resync functionality could be implemented inside the Sync orchestration. Hey guys, some other ideas?

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• Regex one-to-one mapping pattern replace

  - by polygenelubricants

  How would you use regex to write a function that replaces all lowercase letters with uppercase and vice versa? Note: this is NOT a homework question. See also my previous explorations of regex: Regex split into overlapping strings (Alan Moore's answer is especially instructive) Can you use zero-width matching regex in String split? (my solution exploits a known Java regex bug with regards to non-obvious length lookbehind!)

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• Making dtSearch highlight one hit per phrase, rather than one hit per word-in-a-phrase

  - by Chris

  I'm using dtSearch to highlight text search matches within a document. The code to do this, minus some details and cleanup, is roughly along these lines: SearchJob sj = new SearchJob(); sj.Request = "\"audit trail\""; // the user query sj.FoldersToSearch.Add(path_to_src_document); sj.Execute(); FileConverter fileConverter = new FileConverter(); fileConverter.SetInputItem(sj.Results, 0); fileConvert.BeforeHit = "<a name=\"HH_%%ThisHit%%\"/><b>"; fileConverter.AfterHit = "</b>"; fileConverter.Execute(); string myHighlightedDoc = fileConverter.OutputString; If I give dtSearch a quoted phrase query like "audit trail" then dtSearch will do hit highlighting like this: An <a name="HH_0"/><b>audit</b> <a name="HH_1"/><b>trail</b> is a fun thing to have an <a name="HH_2"/><b>audit</b> <a name="HH_last"/><b>trail</b> about! Note that each word of the phrase is highlighted separately. Instead, I would like phrases to get highlighted as whole units, like this: An <a name="HH_0"/><b>audit trail</b> is a fun thing to have an <a name="HH_last"/><b>audit trail</b> about! This would A) make highlighting look better, B) improve behavior of my javascript that helps users navigate from hit to hit, and C) give more accurate counts of total # hits. Is there good ways to make dtSearch highlight phrases this way?

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• Postgresql - one database for everyone, or one-database per customer

  - by user337876

  I'm working on a web-based business application where each customer will need to have their own data (think basecamphq.com type model) For scalability and ease-of-upgrades, I'd prefer to have a single database where each customer gets a filtered version of the data. The problem is how to guarantee that they stay sandboxed to their own data. Trying to enforce it in code seems like a disaster waiting to happen. I know Oracle has a way to append a where clause to every query based on a login id, but does Postgresql have anything similar? If not, is there a different design pattern I could use (like creating a view of each table for each customer that filters)? Worse case scenario, what is the performance/memory overhead of having 1000 100M databases vs having a single 1Tb database? I will need to provide backup/restore functionality on a per-customer basis which is dead-simple on a single database but quite a bit trickier if they are sharing the database with other customers.

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