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• Is it possible to definitively identify whether a DML command was issued from a stored procedure?

  - by Ed Harper

  I have inherited a SQL Server 2008 database to which calling applications have access through stored procedures. Each table in the database has a shadow audit table into which Insert/Update/Delete operations for are logged. Performance testing on populating the audit tables showed that inserting the audit records using OUTPUT clauses was 20% or so faster than using triggers, so this has been implemented in the stored procedures. However, because this design cannot track changes made directly to the tables through DML statements issued directly against the tables, triggers have also been implemented which use the value of @@NESTLEVEL to determine whether or not to run the trigger (the assumption being that all DML run through stored procedures will have @@NESTLEVEL 1). i.e. the body of the trigger code looks something like: IF @@NESTLEVEL = 1 -- implies call is direct sql so generate history from here BEGIN ... insert into audit table This design is flawed because it won't track updates where DML statements are executed in dynamic SQL, or any other context where @@NESTLEVEL is raised above 1. Can anyone suggest a completely reliable method we can use in the triggers to execute them only if not triggered by a stored procedure? Or is this (as I suspect) not possible?

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• Failure remediation strategy for File I/O

  - by Brett

  I'm doing buffered IO into a file, both read and write. I'm using fopen(), fseeko(), standard ANSI C file I/O functions. In all cases, I'm writing to a standard local file on a disk. How often do these file I/O operations fail, and what should the strategy be for failures? I'm not exactly looking for stats, but I'm looking for a general purpose statement on how far I should go to handle error conditions. For instance, I think everyone recognizes that malloc() could and probably will fail someday on some user's machine and the developer should check for a NULL being returned, but there is no great remediation strategy since it probably means the system is out of memory. At least, this seems to be the approach taken with malloc() on desktop systems, embedded systems are different. Likewise, is it worth reattempting a file I/O operation, or should I just consider a failure to be basically unrecoverable, etc. I would appreciate some code samples demonstrating proper usage, or a library guide reference that indicates how this is to be handled. Any other data is, of course, welcome.

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• C++ iterators, default initialization and what to use as an uninitialized sentinel.

  - by Hassan Syed

  The Context I have a custom template container class put together from a map and vector. The map resolves a string to an ordinal, and the vector resolves an ordinal (only an initial string to ordinal lookup is done, future references are to the vector) to the entry. The entries are modified intrusively to contain a a bool "assigned" and an iterator_type which is a const_iterator to the container class's map. My container class will use RCF's serialization code (which models boost::serialization) to serialize my container classes to nodes in a network. Serializing iterator's is not possible, or a can of worms, and I can easily regenerate them onces the vectors and maps are serialized on the remote site. The Question I need to default initialize, and be able to test that the iterator has not been assigned to (if it is assigned it is valid, if not it is invalid). Since map iterators are not invalidated upon operations performed on it (unless of course items are removed :D) am I to assume that map<x,y>::end() is a valid sentinel (regardless of the state of the map -- i.e., it could be empty) to initialize to ? I will always have access to the parent map, I'm just unsure wheather end() is the same as the map contents change. I don't want to use another level of indirection (--i.e., boost::optional) to achieve my goal, I'd rather forego compiler checks to correct logic, but it would be nice if I didn't need to. Misc This question exists, but most of its content seems non-sense. Assigning a NULL to an iterator is invalid according to g++ and clang++. This is another similar question, but it focuses on the common use-cases of iterators, which generally tends to be using the iterator to iterate, ofcourse in this use-case the state of the container isn't meant to change whilst iteration is going on.

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• Pseudo-quicksort time complexity

  - by Ord

  I know that quicksort has O(n log n) average time complexity. A pseudo-quicksort (which is only a quicksort when you look at it from far enough away, with a suitably high level of abstraction) that is often used to demonstrate the conciseness of functional languages is as follows (given in Haskell): quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = quicksort [y | y<-xs, y<p] ++ [p] ++ quicksort [y | y<-xs, y>=p] Okay, so I know this thing has problems. The biggest problem with this is that it does not sort in place, which is normally a big advantage of quicksort. Even if that didn't matter, it would still take longer than a typical quicksort because it has to do two passes of the list when it partitions it, and it does costly append operations to splice it back together afterwards. Further, the choice of the first element as the pivot is not the best choice. But even considering all of that, isn't the average time complexity of this quicksort the same as the standard quicksort? Namely, O(n log n)? Because the appends and the partition still have linear time complexity, even if they are inefficient.

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• PHP Socket Server vs node.js: Web Chat

  - by Eliasdx

  I want to program a HTTP WebChat using long-held HTTP requests (Comet), ajax and websockets (depending on the browser used). Userdatabase is in mysql. Chat is written in PHP except maybe the chat stream itself which could also be written in javascript (node.js): I don't want to start a php process per user as there is no good way to send the chat messages between these php childs. So I thought about writing an own socket server in either PHP or node.js which should be able to handle more then 1000 connections (chat users). As a purely web developer (php) I'm not much familiar with sockets as I usually let web server care about connections. The chat messages won't be saved on disk nor in mysql but in RAM as an array or object for best speed. As far as I know there is no way to handle multiple connections at the same time in a single php process (socket server), however you can accept a great amount of socket connections and process them successive in a loop (read and write; incoming message - write to all socket connections). The problem is that there will most-likely be a lag with ~1000 users and mysql operations could slow the whole thing down which will then affect all users. My question is: Can node.js handle a socket server with better performance? Node.js is event-based but I'm not sure if it can process multiple events at the same time (wouldn't that need multi-threading?) or if there is just an event queue. With an event queue it would be just like php: process user after user. I could also spawn a php process per chat room (much less users) but afaik there are singlethreaded IRC servers which are also capable to handle thousands of users. (written in c++ or whatever) so maybe it's also possible in php. I would prefer PHP over Node.js because then the project would be php-only and not a mixture of programming languages. However if Node can process connections simultaneously I'd probably choose it.

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• Architecting ASP.net MVC App to use repositories and services

  - by zaladane

  Hello, I recently started reading about ASP.net MVC and after getting excited about the concept, i started to migrate all my webform project to MVC but i am having a hard time keeping my controller skinny even after following all the good advices out there (or maybe i just don't get it ... ). The website i deal with has Articles, Videos, Quotes ... and each of these entities have categories, comments, images that can be associated with it. I am using Linq to sql for database operations and for each of these Entities, i have a Repository, and for each repository, i create a service to be used in the controller. so i have - ArticleRepository ArticleCategoryRepository ArticleCommentRepository and the corresponding service ArticleService ArticleCategoryService ... you see the picture. The problem i have is that i have one controller for article,category and comment because i thought that having ArticleController handle all of that might make sense, but now i have to pass all of the services needed to the Controller constructor. So i would like to know what it is that i am doing wrong. Are my services not designed properly? should i create Bigger service to encapsulate smaller services and use them in my controller? or should i have an articleCategory Controller and an articleComment Controller? A page viewed by the user is made of all of that, thee article to be viewed,the comments associated with it, a listing of the categories to witch it applies ... how can i efficiently break down the controller to keep it "skinny" and solve my headache? Thank you! I hope my question is not too long to be read ...

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• Using a Context Menu to delete from a SQLite database in Android

  - by LordSnoutimus

  Hi, I have created a list view that displays the names and dates of items stored in a SQLite database, now I want to use a Context Menu to modify these items stored in the database such as edit the name, delete, and view. This is the code for the list view: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.listview); SQLiteDatabase myDB = null; myDB = this.openOrCreateDatabase(MY_DB_NAME, MODE_PRIVATE, null); Cursor cur = myDB.rawQuery("SELECT _id, trackname, tracktime" + " FROM " + MY_DB_TABLE, null); ListAdapter adapter = new SimpleCursorAdapter(this, R.layout.listview, cur, new String[] { Constants.TRACK_NAME, Constants.TRACK_TIME}, new int[] { R.id.text1, R.id.text2}); ListView list = (ListView)findViewById(R.id.list); list.setAdapter(adapter); registerForContextMenu(list); } and the Context Menu... public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { super.onCreateContextMenu(menu, v, menuInfo); menu.setHeaderTitle("Track Options"); menu.add(0, CHANGE_NAME, 0, "Change name"); menu.add(0, VIEW_TRACK, 0, "View track"); menu.add(0, SEND_TRACK, 0, "Send track"); menu.add(0, DELETE_TRACK, 0, "Delete track"); } I have used a Switch statement to control the menu items.. public boolean onContextItemSelected(MenuItem item) { switch (item.getItemId()){ case CHANGE_NAME: changename(); return true; case DELETE_TRACK: deletetrack(); return true; default: return super.onContextItemSelected(item); } So how would I go ahead and map the deletetrack(); method to find the ID of the track stored in the database to the item that has been selected in the list view?

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• Does anyone know why my maps only show grid

  - by NickTFried

  I've doubled checked my API key is right and that is right I doubled checked that it was correct. Here is my source and XML could anyone check to see what is wrong. Also I make sure I have internet. <?xml version="1.0" encoding="utf-8"?> <uses-permission android:name="android.permissions.INTERNET"/> <uses-permission android:name="android.permissions.ACCESS_FINE_LOCATION"/> <application android:icon="@drawable/icon" android:label="@string/app_name"> <uses-library android:name="com.google.android.maps" /> <activity android:name=".CadetCommand" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="RedLight"></activity> <activity android:name="PTCalculator"></activity> <activity android:name="LandNav"></activity> </application> <uses-sdk android:minSdkVersion="4"/> package edu.elon.cs.mobile; import com.google.android.maps.MapActivity; import com.google.android.maps.MapView; import android.os.Bundle; public class LandNav extends MapActivity{ public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.landnav); } @Override protected boolean isRouteDisplayed() { return false; } }

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• Java Compiler Creation Help..Please

  - by Brian

  I need some help with my code here...What we are trying to do is make a compiler that will read a file containing Machine Code and converting it to 100 lines of 4 bits example: this code is the machine code being converting to opcode and operands. I need some help please.. thanks 799 798 198 499 1008 1108 899 909 898 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Everything compiles but when I go and run my Test.java I get the following OutPut: Exception in thread "main" java.util.NoSuchElementException: No line found at java.util.Scanner.nextLine(Scanner.java:1516) at Compiler.FirstPass(Compiler.java:22) at Compiler.compile(Compiler.java:11) at Test.main(Test.java:5) Here is my class Compiler: import java.io.*; import java.io.DataOutputStream; import java.util.NoSuchElementException; import java.util.Scanner; class Compiler{ private int lc = 0; private int dc = 99; public void compile(String filename) { SymbolList symbolTable = FirstPass(filename); SecondPass(symbolTable, filename); } public SymbolList FirstPass(String filename) { File file = new File(filename); SymbolList temp = new SymbolList(); int dc = 99; int lc = 0; try{ Scanner scan = new Scanner(file); String line = scan.nextLine(); String[] linearray = line.split(" "); while(line!=null){ if(!linearray[0].equals("REM")){ if(!this.isInstruction(linearray[0])){ linearray[0]=removeColon(linearray[0]); if(this.isInstruction(linearray[1])){ temp.add(new Symbol(linearray[0], lc, null)); lc++; } else { temp.add(new Symbol(linearray[0], dc, Integer.valueOf((linearr\ ay[2])))); dc--; } } else { if(!linearray[0].equals("REM")) lc++; } } try{ line = scan.nextLine(); } catch(NoSuchElementException e){ line=null; break; } linearray = line.split(" "); } } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } return temp; } public String makeFilename(String filename) { return filename + ".ex"; } public String removeColon(String str) { if(str.charAt(str.length()-1) == ':'){ return str.substring(0, str.length()-1); } else { return str; } } public void SecondPass(SymbolList symbolTable, String filename){ try { int dc = 99; //Open file for reading File file = new File(filename); Scanner scan = new Scanner(file); //Make filename of new executable file String newfile = makeFilename(filename); //Open Output Stream for writing new file. FileOutputStream os = new FileOutputStream(filename); DataOutputStream dos = new DataOutputStream(os); //Read First line. Split line by Spaces into linearray. String line = scan.nextLine(); String[] linearray = line.split(" "); while(scan.hasNextLine()){ if(!linearray[0].equals("REM")){ int inst=0, opcode, loc; if(isInstruction(linearray[0])){ opcode = getOpcode(linearray[0]); loc = symbolTable.searchName(linearray[1]).getMemloc(); inst = (opcode*100)+loc; } else if(!isInstruction(linearray[0])){ if(isInstruction(linearray[1])){ opcode = getOpcode(linearray[1]); if(linearray[1].equals("STOP")) inst=0000; else { loc = symbolTable.searchName(linearray[2]).getMemloc(); inst = (opcode*100)+loc; } } if(linearray[1].equals("DC")) dc--; } System.out.println(inst); dos.writeInt(inst); linearray = line.split(" "); } if(scan.hasNextLine()) { line = scan.nextLine(); } } scan.close(); for(int i = lc; i <= dc; i++) { dos.writeInt(0); } for(int i = dc+1; i<100; i++){ dos.writeInt(symbolTable.searchLocation(i).getValue()); if(i!=99) dos.writeInt(0); } dos.close(); os.close(); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } public int getOpcode(String inst){ int toreturn = -1; if(isInstruction(inst)){ if(inst.equals("STOP")) toreturn=0; if(inst.equals("LD")) toreturn=1; if(inst.equals("STO")) toreturn=2; if(inst.equals("ADD")) toreturn=3; if(inst.equals("SUB")) toreturn=4; if(inst.equals("MPY")) toreturn=5; if(inst.equals("DIV")) toreturn=6; if(inst.equals("IN")) toreturn=7; if(inst.equals("OUT")) toreturn=8; if(inst.equals("B")) toreturn=9; if(inst.equals("BGTR")) toreturn=10; if(inst.equals("BZ")) toreturn=11; return toreturn; } else { return -1; } } public boolean isInstruction(String totest){ boolean toreturn = false; String[] labels = {"IN", "LD", "SUB", "BGTR", "BZ", "OUT", "B", "STO", "STOP", "AD\ D", "MTY", "DIV"}; for(int i = 0; i < 12; i++){ if(totest.equals(labels[i])) toreturn = true; } return toreturn; } } And here is my class Computer: import java.io.*; import java.util.NoSuchElementException; import java.util.Scanner; class Computer{ private Cpu cpu; private Input in; private OutPut out; private Memory mem; public Computer() throws IOException { Memory mem = new Memory(100); Input in = new Input(); OutPut out = new OutPut(); Cpu cpu = new Cpu(); System.out.println(in.getInt()); } public void run() throws IOException { cpu.reset(); cpu.setMDR(mem.read(cpu.getMAR())); cpu.fetch2(); while (!cpu.stop()) { cpu.decode(); if (cpu.OutFlag()) OutPut.display(mem.read(cpu.getMAR())); if (cpu.InFlag()) mem.write(cpu.getMDR(),in.getInt()); if (cpu.StoreFlag()) { mem.write(cpu.getMAR(),in.getInt()); cpu.getMDR(); } else { cpu.setMDR(mem.read(cpu.getMAR())); cpu.execute(); cpu.fetch(); cpu.setMDR(mem.read(cpu.getMAR())); cpu.fetch2(); } } } public void load() { mem.loadMemory(); } } Here is my Memory class: import java.io.*; import java.util.NoSuchElementException; import java.util.Scanner; class Memory{ private MemEl[] memArray; private int size; private int[] mem; public Memory(int s) {size = s; memArray = new MemEl[s]; for(int i = 0; i < s; i++) memArray[i] = new MemEl(); } public void write (int loc,int val) {if (loc >=0 && loc < size) memArray[loc].write(val); else System.out.println("Index Not in Domain"); } public int read (int loc) {return memArray[loc].read(); } public void dump() { for(int i = 0; i < size; i++) if(i%1 == 0) System.out.println(memArray[i].read()); else System.out.print(memArray[i].read()); } public void writeTo(int location, int value) { mem[location] = value; } public int readFrom(int location) { return mem[location]; } public int size() { return mem.length; } public void loadMemory() { this.write(0, 799); this.write(1, 798); this.write(2, 198); this.write(3, 499); this.write(4, 1008); this.write(5, 1108); this.write(6, 899); this.write(7, 909); this.write(8, 898); this.write(9, 0000); } public void loadFromFile(String filename){ try { FileReader fr = new FileReader(filename); BufferedReader br = new BufferedReader(fr); String read=null; int towrite=0; int l=0; do{ try{ read=br.readLine(); towrite = Integer.parseInt(read); }catch(Exception e){ } this.write(l, towrite); l++; }while(l<100); }catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } Here is my Test class: public class Test{ public static void main(String[] args) throws java.io.IOException { Compiler compiler = new Compiler(); compiler.compile("program.txt"); } }

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• Finding Palindromes in an Array

  - by Jack L.

  For this assignemnt, I think that I got it right, but when I submit it online, it doesn't list it as correct even though I checked with Eclipse. The prompt: Write a method isPalindrome that accepts an array of Strings as its argument and returns true if that array is a palindrome (if it reads the same forwards as backwards) and /false if not. For example, the array {"alpha", "beta", "gamma", "delta", "gamma", "beta", "alpha"} is a palindrome, so passing that array to your method would return true. Arrays with zero or one element are considered to be palindromes. My code: public static void main(String[] args) { String[] input = new String[6]; //{"aay", "bee", "cee", "cee", "bee", "aay"} Should return true input[0] = "aay"; input[1] = "bee"; input[2] = "cee"; input[3] = "cee"; input[4] = "bee"; input[5] = "aay"; System.out.println(isPalindrome(input)); } public static boolean isPalindrome(String[] input) { for (int i=0; i<input.length; i++) { // Checks each element if (input[i] != input[input.length-1-i]){ return false; // If a single instance of non-symmetry } } return true; // If symmetrical, only one element, or zero elements } As an example, {"aay", "bee", "cee", "cee", "bee", "aay"} returns true in Eclipse, but Practice-It! says it returns false. What is going on?

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• How do you pass a generic delegate argument to a method in .NET 2.0 - UPDATED

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult ''#the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) ''#do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• get Random in ArrayList has error of java.lang.IllegalArgumentException: n must be positive

  - by gabrielle fregil

  In my ArrayList, i have get a random Item from my ArrayList for the equip method. Whenever i use my tester, the terminal window prints java.lang.IllegalArgumentException: n must be positive when I try to call random for the size. I tried to change the value of totalElements to the integer size of the elements, then the error would be an OutOfBoundsExeption import java.util.*; import java.util.Scanner; import java.util.Random; public class GameMaster { private int turn, totalElements; private boolean winner; private Avatar x1; private Avatar x2; private ArrayList<Item> inventory; public GameMaster(Avatar a1, Avatar a2) { x2 = a1; x1 = a2; turn = 1; winner = false; inventory = new ArrayList<Item>(); totalElements = 0; } private void fillInventory() { inventory.add( new Item( "Zealot Blades", true, 8 ) ); inventory.add( new Item( "BFG", true, 13 ) ); inventory.add( new Item( "Synthetic Cloth", false, 7 ) ); // more items inventory.add( new Item( "Gauss Rifle", true, 9 ) ); inventory.add( new Item( "Flight Unit", false, 6 ) ); totalElements = inventory.size(); } public String equip() { Avatar w; String a; if (turn%2==1) w=x2; else w=x1; if (w.beltIsFull()) { a = w.getName() + "'s belt is full. \n"; } else { turn++; Random generator = new Random(); Item rand = inventory.get(generator.nextInt(totalElements)); //terminal window in blueJ: java.lang.IllegalArgumentException: n must be positive a = w.getName()+" is equiped with "+rand.getName()+"."; } return a; }

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• How would I go about sharing variables in a C++ class with Lua?

  - by Nicholas Flynt

  I'm fairly new to Lua, I've been working on trying to implement Lua scripting for logic in a Game Engine I'm putting together. I've had no trouble so far getting Lua up and running through the engine, and I'm able to call Lua functions from C and C functions from Lua. The way the engine works now, each Object class contains a set of variables that the engine can quickly iterate over to draw or process for physics. While game objects all need to access and manipulate these variables in order for the Game Engine itself to see any changes, they are free to create their own variables, a Lua is exceedingly flexible about this so I don't forsee any issues. Anyway, currently the Game Engine side of things are sitting in C land, and I really want them to stay there for performance reasons. So in an ideal world, when spawning a new game object, I'd need to be able to give Lua read/write access to this standard set of variables as part of the Lua object's base class, which its game logic could then proceed to run wild with. So far, I'm keeping two separate tables of objects in place-- Lua spawns a new game object which adds itself to a numerically indexed global table of objects, and then proceeds to call a C++ function, which creates a new GameObject class and registers the Lua index (an int) with the class. So far so good, C++ functions can now see the Lua object and easily perform operations or call functions in Lua land using dostring. What I need to do now is take the C++ variables, part of the GameObject class, and expose them to Lua, and this is where google is failing me. I've encountered a very nice method here which details the process using tags, but I've read that this method is deprecated in favor of metatables. What is the ideal way to accomplish this? Is it worth the hassle of learning how to pass class definitions around using libBind or some equivalent method, or is there a simple way I can just register each variable (once, at spawn time) with the global lua object? What's the "current" best way to do this, as of Lua 5.1.4?

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• Determining polygon intersection and containment

  - by Victor Liu

  I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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• SQL Server INSERT, Scope_Identity() and physical writing to disc

  - by TheBlueSky

  Hello everyone, I have a stored procedure that does, among other stuff, some inserts in different table inside a loop. See the example below for clearer understanding: INSERT INTO T1 VALUES ('something') SET @MyID = Scope_Identity() ... some stuff go here INSERT INTO T2 VALUES (@MyID, 'something else') ... The rest of the procedure These two tables (T1 and T2) have an IDENTITY(1, 1) column in each one of them, let's call them ID1 and ID2; however, after running the procedure in our production database (very busy database) and having more than 6250 records in each table, I have noticed one incident where ID1 does not match ID2! Although normally for each record inserted in T1, there is record inserted in T2 and the identity column in both is incremented consistently. The "wrong" records were something like that: ID1 Col1 ---- --------- 4709 data-4709 4710 data-4710 ID2 ID1 Col1 ---- ---- --------- 4709 4710 data-4709 4710 4709 data-4710 Note the "inverted", ID1 in the second table. Knowing not that much about SQL Server underneath operations, I have put the following "theory", maybe someone can correct me on this. What I think is that because the loop is faster than physically writing to the table, and/or maybe some other thing delayed the writing process, the records were buffered. When it comes the time to write them, they were wrote in no particular order. Is that even possible if no, how to explain the above mentioned scenario? If yes, then I have another question to rise. What if the first insert (from the code above) got delayed? Doesn't that mean I won't get the correct IDENTITY to insert into the second table? If the answer of this is also yes, what can I do to insure the insertion in the two tables will happen in sequence with the correct IDENTITY? I appreciate any comment and information that help me understand this. Thanks in advance.

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• Pre-populate iPhone Safari SQLite DB

  - by Matt Rogish

  I'm working with a PhoneGap app that uses Safari local storage (SQlite DB) via Javascript: http://developer.apple.com/safari/library/documentation/iPhone/Conceptual/SafariJSDatabaseGuide/UsingtheJavascriptDatabase/UsingtheJavascriptDatabase.html On first load, the app creates the database, tables, and populates the data via a series of INSERT statements. If the user closes the app while this processing is happening, then my app database is left in an inconsistent state. What I prefer to do is deploy the SQLite DB as part of my iTunes App packaging so nothing must be populated at app cold start. However, I'm not sure if that is possible -- all of the google hits for this topic that I can find are referring to the core-data provided SQLite which is not what we're using... If it's not possible, could I wrap the entire thing in a transaction and keep re-trying it when the app is restarted? Failing that, I guess I can create a simple table with one boolean column "is_app_db_loaded?" and set it to true after I've processed all my inserts. But that's really gross... Ideas? Thanks!!

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• Node & Redis: Crucial Design Issues in Production Mode

  - by Ali

  This question is a hybrid one, being both technical and system design related. I'm developing the backend of an application that will handle approx. 4K request per second. We are using Node.js being super fast and in terms of our database struction we are using MongoDB, with Redis being a layer between Node and MongoDB handling volatile operations. I'm quite stressed because we are expecting concurrent requests that we need to handle carefully and we are quite close to launch. However I do not believe I've applied the correct approach on redis. I have a class Student, and they constantly change stages(such as 'active', 'doing homework','in lesson' etc. Thus I created a Redis DB for each state. (1 for being 'active', 2 for being 'doing homework'). Above I have the structure of the 'active' students table; xa5p - JSON stringified object #1 pQrW - JSON stringified object #2 active_student_table - {{studentId:'xa5p'}, {studentId:'pQrW'}} Since there is no 'select all keys method' in Redis, I've been suggested to use a set such that when I run command 'smembers' I receive the keys and later on do 'get' for each id in order to find a specific user (lets say that age older than 15). I've been also suggested that in fact I used never use keys in production mode. My question is, no matter how 'conceptual' it is, what specific things I should avoid doing in Node & Redis in production stage?. Are they any issues related to my design? Students must be objects and I sure can list them in a list but I haven't done yet. Is it that crucial in production stage?

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• How to add a new Stage to my default stage?

  - by Raigomaru

  I want to add a new Stage called field to the default stage (i need to place different elements on it later). And then i want to add a bitmap called myBitmap to the field. But nothing happens. I don't understand what should i do... var field:Stage = new Stage(); field.x = 200; field.y = 200; field.width = 300; field.height = 300; stage.addChild(field); var bdWidth:Number = 100; var bdHeight:Number = 100; var bdTransparent:Boolean = true; var bdFillColorARGB:uint = 0xFF007090; var myBitmapData:BitmapData = new BitmapData(bdWidth, bdHeight, bdTransparent, bdFillColorARGB); var myBitmap:Bitmap = new Bitmap(myBitmapData); myBitmap.x = 10; myBitmap.y = 10; field.addChild(myBitmap);

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• Seam @Factory in abstract base class?

  - by Shadowman

  I've got a series of web actions I'm implementing in Seam to perform create, read, update, etc. operations. For my read/update/delete actions, I'd like to have individual action classes that all extend an abstract base class. I'd like to put the @Factory method in the abstract base class to retrieve the item that is to be acted upon. For example, I have this as the base class: public abstract class BaseAction { @In(required=false)@Out(required=false) private MyItem item=null; public MyItem getItem(){...} public void setItem(...){...} @Factory("item") public void initItem(){...} } My subclasses would extend BaseAction, so that I don't have to repeat the logic to load the item that is to be viewed, deleted, updated, etc. However, when I start my application, Seam throws errors saying I have declared multiple @Factory's for the same object. Is there any way around this? Is there any way to provide the @Factory in the base class without encoutnering these errors?

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• How do I find all paths through a set of given nodes in a DAG?

  - by Hanno Fietz

  I have a list of items (blue nodes below) which are categorized by the users of my application. The categories themselves can be grouped and categorized themselves. The resulting structure can be represented as a Directed Acyclic Graph (DAG) where the items are sinks at the bottom of the graph's topology and the top categories are sources. Note that while some of the categories might be well defined, a lot is going to be user defined and might be very messy. Example: On that structure, I want to perform the following operations: find all items (sinks) below a particular node (all items in Europe) find all paths (if any) that pass through all of a set of n nodes (all items sent via SMTP from example.com) find all nodes that lie below all of a set of nodes (intersection: goyish brown foods) The first seems quite straightforward: start at the node, follow all possible paths to the bottom and collect the items there. However, is there a faster approach? Remembering the nodes I already passed through probably helps avoiding unnecessary repetition, but are there more optimizations? How do I go about the second one? It seems that the first step would be to determine the height of each node in the set, as to determine at which one(s) to start and then find all paths below that which include the rest of the set. But is this the best (or even a good) approach? The graph traversal algorithms listed at Wikipedia all seem to be concerned with either finding a particular node or the shortest or otherwise most effective route between two nodes. I think both is not what I want, or did I just fail to see how this applies to my problem? Where else should I read?

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• Connecting to SQL Server 2005 via Web Service

  - by clear-cycle-corp

  Delphi 2010, dbExpress, and SQL Server 2005 DB I am trying to make a connection to a SQL Server 2005 DB using Delphi 2010 & DBExpress. If I create a standard delphi application and hard code my connection (IT WORKS!): procedure TForm1.Button1Click(Sender: TObject); var Conn: TSQLConnection; begin Conn:= TSQLConnection.Create(nil); Conn.ConnectionName:= 'VPUCDS_VPN_SE01'; Conn.LoadParamsOnConnect := True; Conn.LoginPrompt:=True; try Conn.Connected:= True; if Conn.Connected then ShowMessage('Connected!') else ShowMessage('NOT Connected!') finally Conn.Free; end; end; All the ini files, and DLLs reside in the same folder as my executable and yes, I have DBXMsSQL & MidasLib in the uses clause again, it works if its not a web service! However, if i then move the code over to a Web services CGI module: function TTest.ConnectToDB: Boolean;stdcall; var Conn: TSQLConnection; begin Conn:= TSQLConnection.Create(nil); Conn.ConnectionName:= 'VPUCDS_VPN_SE01'; Conn.LoadParamsOnConnect := True; Conn.LoginPrompt:=True; try Conn.Connected:= True; result:= Conn.Connected; finally Conn.Free; end; end; Thanks

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• iPhone: Does it ever make sense for an object to retain its delegate?

  - by randombits

  According to the rules of memory management in a non garbage collected world, one is not supposed to retain a the calling object in a delegate. Scenario goes like this: I have a class that inherits from UITableViewController and contains a search bar. I run expensive search operations in a secondary thread. This is all done with an NSOperationQueue and subclasses NSOperation instances. I pass the controller as a delegate that adheres to a callback protocol into the NSOperation. There are edge cases when the application crashes because once an item is selected from the UITableViewController, I dismiss it and thus its retain count goes to 0 and dealloc gets invoked on it. The delegate didn't get to send its message in time as the results are being passed at about the same time the dealloc happens. Should I design this differently? Should I call retain on my controller from the delegate to ensure it exists until the NSOperation itself is dealloc'd? Will this cause a memory leak? Right now if I put a retain on the controller, the crashes goes away. I don't want to leak memory though and need to understand if there are cases where retaining the delegate makes sense. Just to recap. UITableViewController creates an NSOperationQueue and NSOperation that gets embedded into the queue. The UITableViewController passes itself as a delegate to NSOperation. NSOperation calls a method on UITableViewController when it's ready. If I retain the UITableViewController, I guarantee it's there, but I'm not sure if I'm leaking memory. If I only use an assign property, edge cases occur where the UITableViewController gets dealloc'd and objc_msgSend() gets called on an object that doesn't exist in memory and a crash is imminent.

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• Disable validation in an object in Ruby on Rails

  - by J. Pablo Fernández

  I have an object which whether validation happens or not should depend on a boolean, or in another way, validation is optional. I haven't found a clean way to do it. What I'm currently doing is this (disclaimer: you cannot unsee, leave this page if you are too sensitive): def valid? if perform_validation super else super # Call valid? so that callbacks get called and things like encrypting passwords and generating salt in before_validation actually happen errors.clear # but then clear the errors true # and claim ourselves to be valid. This is super hacky! end end Any better ways? Before you point to the :if argument of many validations, this is for a user model which is using authlogic so it has a lot of validation rules. You can stop reading here if you belive me. If you don't, authlogic already sets some :ifs like: :if => :email_changed? which I have to turn into :if => Proc.new {|user| user.email_changed? and user.perform_validation} and in some other cases, since I'm also using authlogic-oid (OpenID) I just don't have control over the :if, authlogic-oid sets it in a way I cannot change it (in time) without further monkey patching. So I have to override seemingly unrelated functions, catch exceptions if a method doesn't exist, etc. The previous hacky solution if the best of my two attempts.

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• Searching with MATCH(), AGAINST() and AS score with mysqli and php

  - by Drew

  Below is the code I am using to search my table. I have made the relevant columns FULLTEXT in the table. This doesn't return me anything. Can someone tell me what it is that i'm doing wrong? Thanks in advance. $sql = 'SELECT id,uname,class,school, MATCH(uname, class, school) AGAINST(?) AS score FROM images WHERE MATCH(uname, class, school) AGAINST(? IN BOOLEAN MODE) ORDER BY score DES'; $stmt = $db_connection->prepare($sql); $stmt->bind_param('ss',$keyword,$keyword); $stmt->execute(); $stmt->store_result(); $stmt->bind_result($id,$uname,$class,$school); $xml = "<data>".PHP_EOL; while($stmt->fetch()){ $xml .= " <person>".PHP_EOL; $xml .= " <id>$id</id>".PHP_EOL; $xml .= " <name>$uname</name>".PHP_EOL; $xml .= " <class>$class</class>".PHP_EOL; $xml .= " <school>$school</school>".PHP_EOL; $xml .= " </person>".PHP_EOL; } $xml .= "</data>"; echo $xml; Below is an image of the indexes of the table:

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• Django unit testing: South-migrated DB works in MySQL, throws duplicate PK error in PostGreSQL. Am I

  - by unclaimedbaggage

  Hi folks, (Worth starting off with a disclaimer: I'm very new to PostGreSQL) I have a django site which involves a standard app/tests.py testing file. If I migrate the DB to MySQL (through South),, the tests all pass. However in PostGresQL, I'm getting the following error: IntegrityError: duplicate key value violates unique constraint "business_contact_pkey" Note this happens while unit testing only - the actual page runs fine in both MySQL & PostGresql. Really having a heckuva time figuring this one out. Anyone have ideas? Below are the Postgresql "\d business_contact" & offending tests.py method if they help. No changes made to either DB except the (same) South migrations Thanks first_name | character varying(200) | not null mobile_phone | character varying(100) | surname | character varying(200) | not null business_id | integer | not null created | timestamp with time zone | not null deleted | boolean | not null default false updated | timestamp with time zone | not null slug | character varying(150) | not null phone | character varying(100) | email | character varying(75) | id | integer | not null default nextval('business_contact_id_seq'::regclass) Indexes: "business_contact_pkey" PRIMARY KEY, btree (id) "business_contact_slug_key" UNIQUE, btree (slug) "business_contact_business_id" btree (business_id) Foreign-key constraints: "business_id_refs_id_772cc1b7b40f4b36" FOREIGN KEY (business_id) REFERENCES business(id) DEFERRABLE INITIALLY DEFERRED Referenced by: TABLE "business" CONSTRAINT "primary_contact_id_refs_id_dfaf59c4041c850" FOREIGN KEY (primary_contact_id) REFERENCES business_contact(id) DEFERRABLE INITIALLY DEFERRED TEST DEF: def test_add_business_contact(self): """ Add a business contact """ contact_slug = 'test-new-contact-added-new-adf' business_id = 1 business = Business.objects.get(id=business_id) postdata = { 'first_name': 'Test', 'surname': 'User', 'business': '1', 'slug': contact_slug, 'email': '[email protected]', 'phone': '12345678', 'mobile_phone': '9823452', 'business': 1, 'business_id': 1, } #Test to ensure contacts that should not exist are not returned contact_not_exists = Contact.objects.filter(slug=contact_slug) self.assertFalse(contact_not_exists) #Add the contact and ensure it is present in the DB afterwards """ contact_add_url = '%s%s/contact/add/' % (settings.BUSINESS_URL, business.slug) self.client.post(contact_add_url, postdata) added_contact = Contact.objects.filter(slug=contact_slug) print added_contact try: self.assertTrue(added_contact) except: formset = ContactForm(postdata) print formset.errors self.assertFalse(True, "Contact not found in the database - most likely, the post values in the test didn't validate against the form")

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