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• SQL Server Index cost

  - by yellowstar

  I have read that one of the tradeoffs for adding table indexes in SQL Server is the increased cost of insert/update/delete queries to benefit the performance of select queries. I can conceptually understand what happens in the case of an insert because SQL Server has to write entries into each index matching the new rows, but update and delete are a little more murky to me because I can't quite wrap my head around what the database engine has to do. Let's take DELETE as an example and assume I have the following schema (pardon the pseudo-SQL) TABLE Foo col1 int ,col2 int ,col3 int ,col4 int PRIMARY KEY (col1,col2) INDEX IX_1 col3 INCLUDE col4 Now, if I issue the statement DELETE FROM Foo WHERE col1=12 AND col2 > 34 I understand what the engine must do to update the table (or clustered index if you prefer). The index is set up to make it easy to find the range of rows to be removed and do so. However, at this point it also needs to update IX_1 and the query that I gave it gives no obvious efficient way for the database engine to find the rows to update. Is it forced to do a full index scan at this point? Does the engine read the rows from the clustered index first and generate a smarter internal delete against the index? It might help me to wrap my head around this if I understood better what is going on under the hood, but I guess my real question is this. I have a database that is spending a significant amount of time in delete and I'm trying to figure out what I can do about it. When I display the execution plan for the deletion, it just shows an entry for "Clustered Index Delete" on table Foo which lists in the details section the other indices that need to be updated but I don't get any indication of the relative cost of these other indices. Are they all equal in this case? Is there some way that I can estimate the impact of removing one or more of these indices without having to actually try it?

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• OutOfMemoryException when I read FileStream 500 MB

  - by Alhambra Eidos

  Hi all, I'm using Filestream for read big file ( 500 MB) and I get the OutOfMemoryException. Any solutions about it. My Code is: using (var fs3 = new FileStream(filePath2, FileMode.Open, FileAccess.Read)) { byte[] b2 = ReadFully(fs3, 1024); } public static byte[] ReadFully(Stream stream, int initialLength) { // If we've been passed an unhelpful initial length, just // use 32K. if (initialLength < 1) { initialLength = 32768; } byte[] buffer = new byte[initialLength]; int read = 0; int chunk; while ((chunk = stream.Read(buffer, read, buffer.Length - read)) > 0) { read += chunk; // If we've reached the end of our buffer, check to see if there's // any more information if (read == buffer.Length) { int nextByte = stream.ReadByte(); // End of stream? If so, we're done if (nextByte == -1) { return buffer; } // Nope. Resize the buffer, put in the byte we've just // read, and continue byte[] newBuffer = new byte[buffer.Length * 2]; Array.Copy(buffer, newBuffer, buffer.Length); newBuffer[read] = (byte)nextByte; buffer = newBuffer; read++; } } // Buffer is now too big. Shrink it. byte[] ret = new byte[read]; Array.Copy(buffer, ret, read); return ret; } thanks in advanced,

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• How to pass parameters to manage_shared_memory.construct() in Boost.Interprocess

  - by recipriversexclusion

  I've stared at the Boost.Interprocess documentation for hours but still haven't been able to figure this out. In the doc, they have an example of creating a vector in shared memory like so: //Define an STL compatible allocator of ints that allocates from the managed_shared_memory. //This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef vector<int, ShmemAllocator> MyVector; int main(int argc, char *argv[]) { //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a vector named "MyVector" in shared memory with argument alloc_inst MyVector *myvector = segment.construct<MyVector>("MyVector")(alloc_inst); Now, I understand this. What I'm stuck is how to pass a second parameter to segment.construct() to specify the number of elements. The interprocess document gives the prototype for construct() as MyType *ptr = managed_memory_segment.construct<MyType>("Name") (par1, par2...); but when I try MyVector *myvector = segment.construct<MyVector>("MyVector")(100, alloc_inst); I get compilation errors. My questions are: Who actually gets passed the parameters par1, par2 from segment.construct, the constructor of the object, e.g. vector? My understanding is that the template allocator parameter is being passed. Is that correct? How can I add another parameter, in addition to alloc_inst that is required by the constructor of the object being created in shared memory? There's very little information other than the terse Boost docs on this.

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• Loading machinecode from file into memory and executing in C -- mprotect failing

  - by chartreusekitsune

  Hi I'm trying to load raw machine code into memory and run it from within a C program, right now when the program executes it breaks when trying to run mprotect on the memory to make it executable. I'm also not entirely sure that if the memory does get set right it will execute. What I currently have is the following: #include <memory.h> #include <sys/mman.h> #include <stdio.h> int main ( int argc, char **argv ) { FILE *fp; int sz = 0; char *membuf; int output = 0; fp = fopen(argv[1],"rb"); if(fp == NULL) { printf("Failed to open file, aborting!\n"); exit(1); } fseek(fp, 0L, SEEK_END); sz = ftell(fp); fseek(fp, 0L, SEEK_SET); membuf = (char *)malloc(sz*sizeof(char)); if(membuf == NULL) { printf("Failed to allocate memory, aborting!\n"); exit(1); } memset(membuf, 0x90, sz*sizeof(char)); if( mprotect(membuf, sz*sizeof(char), PROT_EXEC | PROT_READ | PROT_WRITE) == -1) { printf("mprotect failed!!! aborting!\n"); exit(1); } if((sz*sizeof(char)) != fread(membuf, sz*sizeof(char), 1, fp)) { printf("Read failed, aborting!\n"); exit(1); } __asm__ ( "call %%eax;" : "=a" (output) : "a" (membuf) ); printf("Output = %x\n", output); return 0; }

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• Java and dynamic variables

  - by Arvanem

  Hi folks, I am wondering whether it is possible to make dynamic variables in Java. In other words, variables that change depending on my instructions. FYI, I am making a trading program. A given merchant will have an array of items for sale for various prices. The dynamism I am calling for comes in because each category of items for sale has its own properties. For example, a book item has two properties: int pages, and boolean hardCover. In contrast, a bookmark item has one property, String pattern. Here are skeleton snippets of code so you can see what I am trying to do: public class Merchants extends /* certain parent class */ { // only 10 items for sale to begin with Stock[] itemsForSale = new Stock[10]; // Array holding Merchants public static Merchants[] merchantsArray = new Merchants[maxArrayLength]; // method to fill array of stock goes here } and public class Stock { int stockPrice; int stockQuantity; String stockType; // e.g. book and bookmark // Dynamic variables here, but they should only be invoked depending on stockType int pages; boolean hardCover; String pattern; }

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• puzzled with java if else performance

  - by user1906966

  I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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• How do I repass a function pointer in C++

  - by fneep

  Firstly, I am very new to function pointers and their horrible syntax so play nice. I am writing a method to filter all pixels in my bitmap based on a function that I pass in. I have written the method to dereference it and call it in the pixel buffer but I also need a wrapper method in my bitmap class that takes the function pointer and passes it on. How do I do it? What is the syntax? I'm a little stumped. Here is my code with all the irrelevant bits stripped out and files combined (read all variables initialized filled etc.). struct sColour { unsigned char r, g, b, a; }; class cPixelBuffer { private: sColour* _pixels; int _width; int _height; int _buffersize; public: void FilterAll(sColour (*FilterFunc)(sColour)); }; void cPixelBuffer::FilterAll(sColour (*FilterFunc)(sColour)) { // fast fast fast hacky FAST for (int i = 0; i < _buffersize; i++) { _pixels[i] = (*FilterFunc)(_pixels[i]); } } class cBitmap { private: cPixelBuffer* _pixels; public: inline void cBitmap::Filter(sColour (*FilterFunc)(sColour)) { //HERE!! } };

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• Changing associativity

  - by Sorush Rabiee

  Hi... The associativity of stream insertion operator is rtl, forgetting this fact sometimes cause to runtime or logical errors. for example: 1st- int F() { static int internal_counter c=0; return ++c; } in the main function: //....here is main() cout<<”1st=”<<F()<<”,2nd=”<<F()<<”,3rd=”<<F(); and the output is: 1st=3,2nd=2,3rd=1 that is different from what we expect at first look. 2nd- suppose that we have an implementation of stack data structure like this: // //... a Stack<DataType> class …… // Stack<int> st(10); for(int i=1;i<11;i++) st.push(i); cout<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl<<st.pop()<<endl; expected output is something like: 10 9 8 7 but we have: 7 8 9 10 There is no internal bug of << implementation but it can be so confusing... and finally[:-)] my question: is there any way to change assocativity of an operator by overloading it?

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• Windows Screensaver Multi Monitor Problem

  - by Bryan

  I have a simple screensaver that I've written, which has been deployed to all of our company's client PCs. As most of our PCs have dual monitors, I took care to ensure that the screensaver ran on both displays. This works fine, however on some systems, where the primary screen has been swapped (to the left monitor), the screensaver only works on the left (primary) screen. The offending code is below. Can anyone see anything I've done wrong, or a better way of handling this? For info, the context of "this", is the screensaver form itself. // Make form full screen and on top of all other forms int minY = 0; int maxY = 0; int maxX = 0; int minX = 0; foreach (Screen screen in Screen.AllScreens) { // Find the bounds of all screens attached to the system if (screen.Bounds.Left < minX) minX = screen.Bounds.Left; if (screen.Bounds.Width > maxX) maxX = screen.Bounds.Width; if (screen.Bounds.Bottom < minY) minY = screen.Bounds.Bottom; if (screen.Bounds.Height > maxY) maxY = screen.Bounds.Height; } // Set the location and size of the form, so that it // fills the bounds of all screens attached to the system Location = new Point(minX, minY); Height = maxY - minY; Width = maxX - minX; Cursor.Hide(); TopMost = true;

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• Efficient splitting of elements in a field

  - by Gary

  I have a field in a text file exported from a database. The field contains addresses but sometimes they are quite long and the database allows them to contain multiple lines. When exported, the newline character gets replaced with a dollar sign like this: first part of very long address$second part of very long address$third part of very long address Not every address has multiple lines and no address contains more than three lines. The length of each line is variable. I'm massaging the data for import into MS Access which is used for a mailmerge. I want to split the field on the $ sign if it's there but if the field only contains 1 line, I want to set my two extra output fields to a zero length string so that I don't wind up with blank lines in the address when it gets printed. I have an awk file that's working correctly on all the other data in the textfile but I need to get this last bit working. I tried the below code. Aside from the fact that I get a syntax error at the else, I'm not sure this is a good way to do what I want. This is being done with gawk on Windows. BEGIN { FS = "|" } $1 != "HEADER" { if ($6 ~ /\$/) split($6, arr, "$") address = arr[1] addresstwo = arr[2] addressthree = arr[3] addressLength = length(address) addressTwoLength = length(addresstwo) addressThreeLength = length(addressthree) else { address = $6 addressLength = length($6) addresstwo = "" addressTwoLength = length(addresstwo) addressthree = "" addressThreeLength = length(addressthree) } printf("%*s\t%*s\t\%*s\n", addressLength, address, addressTwoLength, addresstwo, addressThreeLength, addressthree) }

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• Java XMLRPC request-String

  - by Philip

  Hi, I'm using Apache XML-RPC 3.1.2 to talk to an online-service. They have something special, they need a hash over the whole XML with a secret key for some kind of security, like this: String hash = md5(xmlRequest + secretKey); String requestURL = "http://foo.bar/?authHash=" + hash; So I need the XML-request like this: <?xml version="1.0"?> <methodCall> <methodName>foo.bar</methodName> <params> <param> <value><struct> <member><name>bla</name> <value><int>1</int></value> </member> <member><name>blubb</name> <value><int>2</int></value> </member> </struct></value> </param> </params> </methodCall> But how do I get this String-representation of the XMLRPC-Request with the lib Apache XML-RPC?

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• rotate an image aroound a point

  - by Girish

  Hi all, I have an image which is of rectangular dimension, eg 30 x 60 pixels I want to rotate this image around the bottom center of the image, i.e i want to set the pivot in the above example as (15, 60 )pixel. I am using a drawble and matrix to get this done, whatever i try i always end up rotating around center of the image. Code is : Bitmap bitmapOrg = BitmapFactory.decodeFile("/sdcard/DCIM/2010-06-01_15-32-42_821.jpg"); // float angle = (angle + 10.0f)%360.0f; if(null !=bitmapOrg) { int width = bitmapOrg.getWidth(); int height = bitmapOrg.getHeight(); int newWidth = 15; int newHeight = 15; // calculate the scale - in this case = 0.4f float scaleWidth = ((float) newWidth) / width; float scaleHeight = ((float) newHeight) / height; /* Canvas c = new Canvas(bitmapOrg); float px = ; float py; c.rotate(angle, px, py)*/ // createa matrix for the manipulation Matrix matrix = new Matrix(); // resize the bit map matrix.postScale(scaleWidth, scaleHeight); // rotate the Bitmap // matrix.postRotate(45); // recreate the new Bitmap Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true); // make a Drawable from Bitmap to allow to set the BitMap // to the ImageView, ImageButton or what ever BitmapDrawable bmd = new BitmapDrawable(resizedBitmap); ImageView imageView = new ImageView(this); // set the Drawable on the ImageView imageView.setImageDrawable(bmd); // center the Image imageView.setScaleType(ScaleType.CENTER); // imageView.layout(100, 300, 0, 0); // linLayout.addView(imageView); // add ImageView to the Layout linLayout.addView(imageView, new AbsoluteLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 10, 30 ) ); can anyone let me know how to get this rectified?

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• How does the destructor know when to activate itself? Can it be relied upon?

  - by Robert Mason

  Say for example i have the following code (pure example): class a { int * p; public: a() { p = new int; ~a() { delete p; } }; a * returnnew() { a retval; return(&retval); } int main() { a * foo = returnnew(); return 0; } In returnnew(), would retval be destructed after the return of the function (when retval goes out of scope)? Or would it disable automatic destruction after i returned the address and i would be able to say delete foo; at the end of main()? Or, in a similar vein (pseudocode): void foo(void* arg) { bar = (a*)arg; //do stuff exit_thread(); } int main() { while(true) { a asdf; create_thread(foo, (void*)&asdf); } return 0; } where would the destructor go? where would i have to say delete? or is this undefined behavior? Would the only possible solution be to use the STL referenced-counted pointers? how would this be implemented? Thank you- i've used C++ for a while but never quite been in this type of situation, and don't want to create memory leaks.

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• Error when calling SQL SP via LINQ

  - by PaulC

  Newbie problem: I have a SQL SP with ten parameters (eight input, two output) but when I attempt to call it via LINQ from code I get the following error message: "The best overloaded method match for 'DataClassesDataContext.ST_CR_CREATE_CASE_BASIS(string, string, string, string, System.DateTime?, string, string, string, ref int?, ref int?)' has some invalid arguments". The params with ? appear to be unrecognized, but I'm baffled: the data types match the SQL types, the number of parameters match, the other parmeters don't exhibit the same behaviour. Can anyone tell me what's going on? Thanks in advance. -- SQL SP: create procedure ST_CR_CREATE_CASE_BASIS @p_Pers_No nvarchar (50), @p_Subject nvarchar (255), @p_RQ_XML nvarchar(max), @p_RQ_XSL nvarchar(max), @p_Date_Submit smalldatetime, @p_User_ID_Submit nvarchar (255), @p_RQ_Status nvarchar (50), @p_User_ID_OnBehalf nvarchar (255), @p_Case_Number int output, @p_RQ_ID int output as begin -- ... etc.; the SP works fine when called from SSMS The code-behind proc from the aspx page looks like this: protected void cmdSubmit_Click(object sender, EventArgs e) { using (DataClassesDataContext vDataCont = new DataClassesDataContext()) { Int32 vNewCaseNr; Int32 vNewReqNr; DateTime vNow = System.DateTime.Now; vDataCont.ST_CR_CREATE_CASE_BASIS("101", "Test Subject Late Wed", null, null, vNow , "101", "1", "101", ref vNewCaseNr, vNewReqNr); } }

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• Does isEmpty method in Stream evaluate the whole Stream?

  - by abhin4v

  In Scala, does calling isEmtpy method on an instance of Stream class cause the stream to be evaluated completely? My code is like this: import Stream.cons private val odds: Stream[Int] = cons(3, odds.map(_ + 2)) private val primes: Stream[Int] = cons(2, odds filter isPrime) private def isPrime(n: Int): Boolean = n match { case 1 => false case 2 => true case 3 => true case 5 => true case 7 => true case x if n % 3 == 0 => false case x if n % 5 == 0 => false case x if n % 7 == 0 => false case x if (x + 1) % 6 == 0 || (x - 1) % 6 == 0 => true case x => primeDivisors(x) isEmpty } import Math.{sqrt, ceil} private def primeDivisors(n: Int) = primes takeWhile { _ <= ceil(sqrt(n))} filter {n % _ == 0 } So, does the call to isEmpty on the line case x => primeDivisors(x) isEmpty cause all the prime divisors to be evaluated or only the first one?

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• junit assert in thread throws exception

  - by antony.trupe

  What am I doing wrong that an exception is thrown instead of showing a failure, or should I not have assertions inside threads? @Test public void testComplex() throws InterruptedException { int loops = 10; for (int i = 0; i < loops; i++) { final int j = i; new Thread() { @Override public void run() { ApiProxy.setEnvironmentForCurrentThread(env);//ignore this new CounterFactory().getCounter("test").increment();//ignore this too int count2 = new CounterFactory().getCounter("test").getCount();//ignore assertEquals(j, count2);//here be exceptions thrown. this is line 75 } }.start(); } Thread.sleep(5 * 1000); assertEquals(loops, new CounterFactory().getCounter("test").getCount()); } StackTrace Exception in thread "Thread-26" junit.framework.AssertionFailedError: expected:<5> but was:<6> at junit.framework.Assert.fail(Assert.java:47) at junit.framework.Assert.failNotEquals(Assert.java:277) at junit.framework.Assert.assertEquals(Assert.java:64) at junit.framework.Assert.assertEquals(Assert.java:195) at junit.framework.Assert.assertEquals(Assert.java:201) at com.bitdual.server.dao.ShardedCounterTest$3.run(ShardedCounterTest.java:77)

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• TextBox should display text in hexadecimal in a specific format

  - by Owais Wani

  I have a textbox in my xaml file which is editable. Now according to my project requirements content in textbox should only be 0-9 and a-f (hexadecimal values) and textbox should take the input based on hexadecimal values. Demonstratation: 12 ab 32 a5 64 Now if my cursor is at the end and i go on pressing backspace, it shud remove the values as it happens in a general text box. Now If my cursor is at the beginning of a5, and i press "delete key", the value should become like: 12 ab 32 56 4 If my cursor is at the end of a5 and i press the 'delete key" nothing should happen. I had done this successful in my C++ application as follows: void CMSP430CommPanel::textEditorTextChanged (TextEditor& editor) { if(&editor == m_texti2cWrite) { int count = 0; int location; String text1 = m_texti2cWrite->getText(); String text = m_texti2cWrite->getText().removeCharacters(" "); String hexString = String::empty; int countCaret = m_texti2cWrite->getCaretPosition(); for(int i=0; i < text.length(); i++) { hexString = hexString + String (&text[i], 1); if((i+1) % 2 == 0) { if(i != text.length()-1) { hexString = hexString + T(" "); count ++; } } count ++; } m_texti2cWrite->setText(hexString,false); if(text1.length() == m_texti2cWrite->getCaretPosition()) { m_texti2cWrite->setCaretPosition(count); } else { m_texti2cWrite->setCaretPosition(countCaret); } } } where m_texti2cWrite is the name given to textbox. How can i implement the same case in my wpf application which is MVVM based. I have a textbox which shud take inputs as I said above. please help!!!

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• Is there any other efficient way to use table variable instead of using temporary table

  - by varta shrimali

  we are writing script to display banners on a web page where we are using temporary table in mysql procedure. Is there any other efficient way to use table variable instead of using temporary table we are using following code: -- banner location CURSOR -- DECLARE banner_location_cursor CURSOR FOR select bm.id as masterId, bm.section as masterName, bs.id as locationId, bs.sectionName as locationName from banner_master as bm inner join banner_section as bs on bm.id=bs.masterId where bm.section=sCode ; -- DECLARE banner CURSORS DECLARE banner_cursor CURSOR FOR SELECT bd.id as bannerId, bd.sectionId, bd.bannerName, bd.websiteURL, bd.paymentType, bd.status, bd.startDate, bd.endDate, bd.bannerDisplayed, bs.id, bs.sectionName from banner_detail as bd inner join banner_section as bs on bs.id=bd.sectionId where bs.id= location_id and bd.status='A' and (dates between cast(bd.startDate as DATE) and cast(bd.endDate as DATE)) order by rand(), bd.bannerDisplayed asc limit 1 ; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_rows = 1; SET dates = (select curdate()); -- RESULTS TABLE WHICH WILL BE RETURNED -- CREATE temporary TABLE test ( b_id INT, s_id INT, b_name varchar(128), w_url varchar(128), p_type varchar(128), st char(1), s_date datetime, e_date datetime, b_display int, sec_id int, s_name varchar(128) ); -- OPEN banner location CURSOR OPEN banner_location_cursor; the_loop: LOOP FETCH banner_location_cursor INTO master_id, master_name, location_id, location_name; IF no_more_rows THEN CLOSE banner_location_cursor; leave the_loop; END IF; OPEN banner_cursor; -- select FOUND_ROWS(); the_loop2: LOOP FETCH banner_cursor INTO banner_id, section_id, banner_name, website_url, payment, status, start_date, end_date, banner_displayed, sec_id, section_name; IF no_more_rows THEN set no_more_rows = 0; CLOSE banner_cursor; leave the_loop2; END IF; INSERT INTO test ( b_id, s_id, b_name , w_url, p_type, st, s_date, e_date, b_display, sec_id, s_name ) VALUES ( banner_id, section_id, banner_name, website_url, payment, status, start_date, end_date, banner_displayed, sec_id, section_name ); UPDATE banner_detail set bannerDisplayed = (banner_displayed+1) where id = banner_id; END LOOP the_loop2; END LOOP the_loop; -- RETURN result SELECT * FROM test; -- DROP RESULTS TABLE DROP TABLE test; END

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• Copy vector of values to vector of pairs in one line

  - by Kirill V. Lyadvinsky

  I have the following types: struct X { int x; X( int val ) : x(val) {} }; struct X2 { int x2; X2() : x2() {} }; typedef std::pair<X, X2> pair_t; typedef std::vector<pair_t> pairs_vec_t; typedef std::vector<X> X_vec_t; I need to initialize instance of pairs_vec_t with values from X_vec_t. I use the following code and it works as expected: int main() { pairs_vec_t ps; X_vec_t xs; // this is not empty in the production code ps.reserve( xs.size() ); { // I want to change this block to one line code. struct get_pair { pair_t operator()( const X& value ) { return std::make_pair( value, X2() ); } }; std::transform( xs.begin(), xs.end(), back_inserter(ps), get_pair() ); } return 0; } What I'm trying to do is to reduce my copying block to one line with using boost::bind. This code is not working: for_each( xs.begin(), xs.end(), boost::bind( &pairs_vec_t::push_back, ps, boost::bind( &std::make_pair, _1, X2() ) ) ); I know why it is not working, but I want to know how to make it working without declaring extra functions and structs?

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• Python import error: Symbol not found, but the symbol <s>is</s> *is not* present in the file

  - by Autopulated

  I get this error when I try to import ssrc.spread: ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/ssrc/_spread.so, 2): Symbol not found: __ZN17ssrcspread_v1_0_67Mailbox11ZeroTimeoutE The file in question (_spread.so) includes the symbol: $ nm _spread.so | grep _ZN17ssrcspread_v1_0_67Mailbox11ZeroTimeoutE U __ZN17ssrcspread_v1_0_67Mailbox11ZeroTimeoutE U __ZN17ssrcspread_v1_0_67Mailbox11ZeroTimeoutE (twice because the file is a fat ppc/x86 binary) EDIT: okay, as James points out, the U means that the symbol is undefined but required by the object file. With some more digging I've noticed (where I should have looked first...) these linker errors during compilation: CC=g++ CXX=g++ g++-4.0 -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -O3 -I../.. -I../.. -I/usr/local/include -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -O2 -I/usr/local/include -std=c++98 -pipe -fno-gnu-keywords -fvisibility-inlines-hidden -o SsrcSpread.o -c SsrcSpread.cc CC=g++ CXX=g++ /bin/sh ../../libtool --tag=CXX --mode=link g++-4.0 -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -bundle -undefined dynamic_lookup -F/Library/Frameworks -framework Python \ -pthread -D_REENTRANT -pedantic -Wall -Wno-long-long -Winline -Woverloaded-virtual -Wold-style-cast -Wsign-promo -L../../ssrc -lssrcspread -L/usr/local/lib -ltspread-core -o _spread.so SsrcSpread.o mkdir .libs g++-4.0 -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -bundle -undefined dynamic_lookup -F/Library/Frameworks -framework Python -pthread -D_REENTRANT -pedantic -Wall -Wno-long-long -Winline -Woverloaded-virtual -Wold-style-cast -Wsign-promo -o _spread.so SsrcSpread.o -Wl,-bind_at_load -L/Dev/libssrcspread-1.0.6/ssrc /Dev/libssrcspread-1.0.6/ssrc/.libs/libssrcspread.a -L/usr/local/lib -ltspread-core ld: warning: in ~/Dev/libssrcspread-1.0.6/ssrc/.libs/libssrcspread.a, file was built for unsupported file format which is not the architecture being linked (ppc) ld: warning: in /Developer/SDKs/MacOSX10.4u.sdk/usr/local/lib/libtspread-core.dylib, file was built for unsupported file format which is not the architecture being linked (ppc) ld: warning: in /Dev/libssrcspread-1.0.6/ssrc/.libs/libssrcspread.a, file was built for unsupported file format which is not the architecture being linked (i386) ld: warning: in /Developer/SDKs/MacOSX10.4u.sdk/usr/local/lib/libtspread-core.dylib, file was built for unsupported file format which is not the architecture being linked (i386) I'm also not entirely sure that the 10.4 sdk is the right one for compiling python modules (but switching to 10.6 didn't seem to help).

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• Linq-to-SQL: How to shape the data with group by?

  - by Cheeso

  I have an example database, it contains tables for Movies, People and Credits. The Movie table contains a Title and an Id. The People table contains a Name and an Id. The Credits table relates Movies to the People that worked on those Movies, in a particular role. The table looks like this: CREATE TABLE [dbo].[Credits] ( [Id] [int] IDENTITY (1, 1) NOT NULL PRIMARY KEY, [PersonId] [int] NOT NULL FOREIGN KEY REFERENCES People(Id), [MovieId] [int] NOT NULL FOREIGN KEY REFERENCES Movies(Id), [Role] [char] (1) NULL In this simple example, the [Role] column is a single character, by my convention either 'A' to indicate the person was an actor on that particular movie, or 'D' for director. I'd like to perform a query on a particular person that returns the person's name, plus a list of all the movies the person has worked on, and the roles in those movies. If I were to serialize it to json, it might look like this: { "name" : "Clint Eastwood", "movies" : [ { "title": "Unforgiven", "roles": ["actor", "director"] }, { "title": "Sands of Iwo Jima", "roles": ["director"] }, { "title": "Dirty Harry", "roles": ["actor"] }, ... ] } How can I write a LINQ-to-SQL query that shapes the output like that? I'm having trouble doing it efficiently. if I use this query: int personId = 10007; var persons = from p in db.People where p.Id == personId select new { name = p.Name, movies = (from m in db.Movies join c in db.Credits on m.Id equals c.MovieId where (c.PersonId == personId) select new { title = m.Title, role = (c.Role=="D"?"director":"actor") }) }; I get something like this: { "name" : "Clint Eastwood", "movies" : [ { "title": "Unforgiven", "role": "actor" }, { "title": "Unforgiven", "role": "director" }, { "title": "Sands of Iwo Jima", "role": "director" }, { "title": "Dirty Harry", "role": "actor" }, ... ] } ...but as you can see there's a duplicate of each movie for which Eastwood played multiple roles. How can I shape the output the way I want?

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• .NET Thread.Abort again

  - by hoodoos

  Again I want to talk about safety of the Thread.Abort function. I was interested to have some way to abort operations which I can't control really and don't want actually, but I want to have my threads free as soon as possible to prevent thread thirsty of my application. So I wrote some test code to see if it's possible to use Thread.Abort and have the aborting thread clean up resources propertly. Here's code: int threadRunCount = 0; int threadAbortCount = 0; int threadFinallyCount = 0; int iterations = 0; while( true ) { Thread t = new Thread( () => { threadRunCount++; try { Thread.Sleep( Random.Next( 45, 55 ) ); } catch( ThreadAbortException ) { threadAbortCount++; } finally { threadFinallyCount++; } } ); t.Start(); Thread.Sleep( 45 ); t.Abort(); iterations++; } So, so far this code worked for about 5 mins, and threadRunCount was always equal to threadFinally and threadAbort was somewhat lower in number, because some threads completed with no abort or probably got aborted in finally. So the question is, do I miss something?

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• How to make an entity out of a join table without primary key

  - by tputkonen

  I'm trying to generate JPA entities out of an existing database having an "interesting" design. Database has a table called UserSet, which can have links to several other UserSets. There is a one to many relation between UserSets and LinkedUserSets. LinkedUserSets also has one to one relation to UserSets. I tried to generate a JPA Entity out of the database structure using Dali JPA Tools. The resulting entity Linkeduserset misses @Id or @EmbeddedId annotation and thus failes to compile. As the resulting entity contains only two @JoinColumns (which cannot be marked as @Id), I have not so far found a way around this issue. Database structure can not be modified in any way. Is there a way to overcome this somehow? Relevant pars of create table statements: CREATE TABLE `LinkedUserSets` ( `UsrSetID` INT(11) NOT NULL DEFAULT '0' , `ChildID` INT(11) NOT NULL DEFAULT '0' , CONSTRAINT `fk_LinkedUserSets_UserSet1` FOREIGN KEY (`UsrSetID` ) REFERENCES `UserSet` (`UsrSetID` )); CREATE TABLE `UserSet` ( `UsrSetID` INT(11) NOT NULL AUTO_INCREMENT , PRIMARY KEY (`UsrSetID`), CONSTRAINT `fk_UserSet_LinkedUserSets1` FOREIGN KEY (`UsrSetID` ) REFERENCES `LinkedUserSets` (`ChildID` )); Generated entities: @Entity @Table(name="linkedusersets") public class Linkeduserset { //bi-directional many-to-one association to Userset @ManyToOne @JoinColumn(name="UsrSetID") private Userset userset1; //bi-directional one-to-one association to Userset @OneToOne @JoinColumn(name="ChildID") private Userset userset2; } @Entity @Table(name="userset") public class Userset { private static final long serialVersionUID = 1L; @Id @Column(name="UsrSetID") private int jngSetID; //bi-directional many-to-one association to Linkeduserset @OneToMany(mappedBy="userset1") private Set<Linkeduserset> linkedusersets; //bi-directional one-to-one association to Linkeduserset @OneToOne(mappedBy="userset2") private Linkeduserset linkeduserset; } Error message: Entity "Linkeduserset" has no Id or EmbeddedId

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• C# Multi CheckboxList update inserts checked records but doesn't delete unchecked records

  - by DLL

  I have a multi checkboxlist on a formview. Both use queries in a tableadapter. I'm using VS 2012. When the user updates the form, I use the following code to update the checkbox data. If a user checks a new box, a new record is inserted correctly, however if the user unchecks a box the existing record is not deleted. The delete query works fine if I run it from the query builder in the table adapter, it's reaching the expected line in the code correctly, all values are correct and I receive no errors. I use a similar query to delete records when the form level data is deleted which works fine. The very last line is the one that doesn't work. Query: DELETE FROM [SLA_Categories] WHERE (([SLA_ID] = @SLA_ID) AND ([Choice_ID] = @Choice_ID)) protected void FormView1_ItemUpdating(object sender, FormViewUpdateEventArgs e) { if (FormView1.DataKey.Value != null) { Categs = (CheckBoxList)FormView1.FindControl("CheckBoxList1"); CurrentSLA_ID = (int)FormView1.DataKey.Value; } if (CurrentSLA_ID > 0) { foreach (ListItem li in Categs.Items) { // See if there's a record for the current sla in this category int CurrentChoice_ID = Convert.ToInt32(li.Value); SLADataSetTableAdapters.SLA_CategoriesTableAdapter myAdapter; myAdapter = new SLADataSetTableAdapters.SLA_CategoriesTableAdapter(); int myCount = (int)myAdapter.FindCategoryBySLA_IDAndChoice_ID(CurrentSLA_ID, CurrentChoice_ID); // If this category is checked and there is not an existing rec, insert one if (li.Selected == true && myCount < 1) { // Insert a rec for this sla myAdapter.InsertCategory(CurrentChoice_ID, CurrentSLA_ID); } // If this category is unchecked and there is and existing rec, delete it if (li.Selected == false && myCount > 0) { // Delete this rec myAdapter.DeleteCategoryBySLA_IDAndChoice_ID(CurrentChoice_ID, CurrentSLA_ID); } } } }

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• How can I make this method more Scalalicious

  - by Neil Chambers

  I have a function that calculates the left and right node values for some collection of treeNodes given a simple node.id, node.parentId association. It's very simple and works well enough...but, well, I am wondering if there is a more idiomatic approach. Specifically is there a way to track the left/right values without using some externally tracked value but still keep the tasty recursion. /* * A tree node */ case class TreeNode(val id:String, val parentId: String){ var left: Int = 0 var right: Int = 0 } /* * a method to compute the left/right node values */ def walktree(node: TreeNode) = { /* * increment state for the inner function */ var c = 0 /* * A method to set the increment state */ def increment = { c+=1; c } // poo /* * the tasty inner method * treeNodes is a List[TreeNode] */ def walk(node: TreeNode): Unit = { node.left = increment /* * recurse on all direct descendants */ treeNodes filter( _.parentId == node.id) foreach (walk(_)) node.right = increment } walk(node) } walktree(someRootNode) Edit - The list of nodes is taken from a database. Pulling the nodes into a proper tree would take too much time. I am pulling a flat list into memory and all I have is an association via node id's as pertains to parents and children. Adding left/right node values allows me to get a snapshop of all children (and childrens children) with a single SQL query. The calculation needs to run very quickly in order to maintain data integrity should parent-child associations change (which they do very frequently). In addition to using the awesome Scala collections I've also boosted speed by using parallel processing for some pre/post filtering on the tree nodes. I wanted to find a more idiomatic way of tracking the left/right node values. After looking at the answers listed I have settled on this synthesised version: def walktree(node: TreeNode) = { def walk(node: TreeNode, counter: Int): Int = { node.left = counter node.right = treeNodes .filter( _.parentId == node.id) .foldLeft(counter+1) { (counter, curnode) => walk(curnode, counter) + 1 } node.right } walk(node,1) }

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