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• MySQL indexes: how do they work?

  - by bob-the-destroyer

  I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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• How does mysql define DISTINCT()

  - by goran

  AFAIK SQL defines two uses of DISTINCT keywords - SELECT DISTINCT field... and SELECT COUNT(DISTINCT field) ... However in one of web applications that I administer I've noticed performance issues on queries like SELECT DISTINCT(field1), field2, field3 ... DISTINCT() on a single column makes no sense and I am almost sure it is interpreted as SELECT DISTINCT field1, field2, field3 ... but how can I prove this? I've searched mysql site for a reference on this particular syntax but could not find any. Does anyone have a link to definition of DISTINCT() in mysql or knows about other authoritative source on this? Best

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• Why does this return zero results?

  - by Jon

  I have a List<List<string>> and when I try to search with the List<string> it returns no results. Any ideas? Thanks List<List<string>> test = new List<List<string>>(); List<string> ff = new List<string>(); ff.Add("1"); ff.Add("ABC 1"); test.Add(ff); ff = new List<string>(); ff.Add("2"); ff.Add("ABC 2"); test.Add(ff); var result = test.Where(x=>x.Contains("ABC")); //result.Count(); is 0

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• SQLServer triggers

  - by Evl-ntnt

  Please help me to write trigger that, adds new rows in table I have 3 tables in my database. 1) Regions (id, name); id - primary 2) Technics (id, name); id - primary 3) Availability (id, region, technic, count); id - primary, region - foreign on Regions.id, Technik - foreign on technics.id I want to add new row in Availability for each Technics row on adding row in Regions. Somethink like: procedure void OnAddNewRegion(int region) { foreach (Row r in Technic) { Availability.Rows.Add(new Row(id, region, r.Id, 0)); } } But in SQL trigger. Same I want to do on the adding new Technics row

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• make error in re-building ns2

  - by user3702405

  I have implemented a new routing protocol named AODV2 in ns-2.35. I am using ns-2.35 in fedora 13. All .cc files have a .o file with them that means recompilation is done. But I am getting an error in response to the 'make' command. Error is shown below: trace/cmu-trace.o: In function hdr_aodv2::access(Packet const*)': cmu-trace.cc:(.text._ZN9hdr_aodv26accessEPK6Packet[hdr_aodv2::access(Packet const*)]+0x7): undefined reference tohdr_aodv2::offset_2' collect2: ld returned 1 exit status make: * [ns] Error 1 I don't know how to remove this error, Can anyone help me please? Thanks, Naeem

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• ColumnCount in DataGridView remains 0 after assigning data source

  - by Manan Shah

  I am having trouble with the following simple code List<Car> tempList = new List<Car>(); BindingSource bindingSource = new BindingSource(); bindingSource.DataSource = tempList; dgTempView.DataSource = bindingSource; Here, dgTempView is a data grid view After the above lines execute, the column count in the datagrid view remains 0. And when I try adding a Car instance in tempList, I get an error saying that 'no row can be added to a datagridview control that does not have columns' . I am not able to understand what am I missing here

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• How to set the same column width in a datagrid in flex at runtime?

  - by Ra

  HI, In flex, I have a datagrid with 22 columns. I initially display all the columns. The width of each column right is uniform. Now when i change the visiblity of a few columns, the width of each column varies. How do i maintain a uniform column width for each column whether or not there are any invisible columns?... Also how do i get the count of number of visible columns. the ColumnCount property returns total number of columns and not the number of visible ones.

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• htaccess - rewrite rule issue - not able to get 10th variable

  - by sandeepan-nath

  I am not able to get the 10th variable. I am getting 1st variable appended with a 0(zero) instead. RewriteRule ^(browse_by_exam)/(classes|packs|tutor_search)/([a-zA-Z0-9\.\á\á\â\ä\ã\å\æ\ç\è\é\ê\ë\ì\í\ï\ð\ñ\ò\ó\ô\õ\ö\ø\ù\ú\û\ü\ý\þ\¿\¡\«\»\ÿ\ß\$\*\!\-\=\@\#\%\^\(\)\_\&\{\}\;\,\<\>\?\`\~\[\|\"\'\]\\\ +]+)/([0-1])/([0-9]+)/([0-9]+)/([0-9]+),([0-9]+),([a-z]+),([a-z]+)?$ index.php?a=$1&type=$2&search_text=$3&new_search=$4&search_exam=$5&search_subject=$6&site=$7&count=$8&column=$9&direction=$10 I am not able to get the 10th variable using $_GET['direction'] in my php code - it returns me the 1st variable appended with a 0 i.e. browse_by_exam0. I read in many places about this thing. Here http://www.digimantra.com/tutorials/advanced-htaccess-for-more-than-10-group-of-backtrack-references/, they have given a workaround for the problem - using %1 instead of $10, but that too is not working. Please help. I am completely blocked.

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• Parsec Haskell Lists

  - by Martin

  I'm using Text.ParserCombinators.Parsec and Text.XHtml to parse an input and get a HTML output. If my input is: * First item, First level ** First item, Second level ** Second item, Second level * Second item, First level My output should be: <ul><li>First item, First level <ul><li>First item, Second level </li><li>Second item, Second level </li></ul></li><li>Second item, First level</li></ul> I wrote this, but obviously does not work recursively list= do{ s <- many1 item;return (olist << s) } item= do{ (count 1 (char '*')) ;s <- manyTill anyChar newline ;return ( li << s) } Any ideas? the recursion can be more than two levels Thanks!

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• The type or namespace name 'Oledb' does not exist in the namespace 'System.Data' error on Web Servic

  - by Pankaj Kumar

  Hi everyone... i have a webservice that i want to test by typing the url in the address bar in the web browser localhost:1981/myProject/admin/autocomplete.asmx and when i do this it gives this compilation error CS0234: The type or namespace name 'Oledb' does not exist in the namespace 'System.Data' (are you missing an assembly reference?) i know this is because we added this in our web.config <add namespace="System.Data.Oledb"/> <add namespace ="System.Data"/> in the namespaces section..... when i call this web service through ajax it works but if i try to test it it gives this error. Is there any way to prevent this?

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• Youtube video embed in WebView and MoviePlayer control

  - by Tronic

  hi, i embed a youtube video into a webview. the problem is: when i pop the current view (which includes the webview) from navigation controller, the the movie itself stops, but the audio is continues running. when i push the view controller on the navigation controller again, i can play the movie newly, but the old audio is still there. my webview code ids_ = [NSArray arrayWithObjects:@"2b84g38Z_60",@"3URx0tM-rMc",@"HZpi-2HVhq0",@"Hhns0DRPI44",@"hRuoxRQ4Q3k",@"lkMXwNBGRA8",@"tXGc6wWIFJo",@"uzGdEn8aW-Q",@"ZAoEBdt8C5M",@"vn8EJqt2BvQ",@"7Z_qRbjG6Ck",@"JspRcxGUijs"@"lM2lcVOh5YU",@"2b84g38Z_60",nil]; int numIds_ = [ids_ count]; NSLog(@"%d", arc4random()%numIds_); NSString *youTubeVideoHTML = [[NSString alloc] initWithFormat:@"<html><head></head><body style=\"margin:0;background-color:#000;\"><iframe class=\"youtube-player\" type=\"text/html\" width=\"640\" height=\"365\" src=\"http://www.youtube.com/embed/%@\" frameborder=\"0\"></iframe></body></html>", [ids_ objectAtIndex:arc4random()%numIds_]]; NSLog(youTubeVideoHTML); [youtubeView loadHTMLString:youTubeVideoHTML baseURL:nil]; thanks in advance

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• How to use a dialog in an Excel shared addin

  - by user169867

  I'm writing a shared addin for Excel. It adds a CommandBarButton that when clicked opens a WPF window to collect some information from the user. I wanted to keep the same WPF dialog in memory and reuse it so that if the user clicks the CommandBarButton again their previous values would still be there. So I made a reference to my WPD as a private member of my addin object that implements Extensibility.IDTExtensibility2. I created the window during OnStartupComplete(), but for some reason when I run Excel the window immediately opens even though I never called ShowDialog() and when I do call ShowDialog() when the CommandBarButton is clicked to reOpen the window it fails to load. Does anyone know why this happens and what the correct way to handle this is? Thanks very much for any help.

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• Problem linking SDL_Image against libpng

  - by Tim Jones

  I'm trying to compile SDL_Image 1.2.10 with MinGW + MSys (gcc 4.5.0) on Windows, I have compiled all the requires libs (zlib 1.2.5, libpng 1.4.2, libjpeg 8a, libtiff 3.9.2). SDL_Image compiles fine, but fails to link to libpng, throwing .libs/IMG_png.o:IMG_png.c:(.text+0x16): undefined reference errors on various png structs. If I run ./configure --prefix=/mingw --disable-png for SDL_Image, it compiles and links against the other libs just fine. I have tried older versions of libpng (1.2.43), but they also caused SDL_Image to throw the same errors.

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• Problem getting IM information from an ABRecord

  - by bend0r

  Hello, I'm trying to get the IM account information from existing contacts (adressbook) on iPhone. I walk through the contacts and I get the contacts which have an entry in IM but I can't read the jabber-address. abArray = (NSArray *)ABAddressBookCopyArrayOfAllPeople(ABAddressBookCreate()); for(int i=0 ; i<[abArray count];i++) { ABRecordRef record = [abArray objectAtIndex:i]; ABMutableMultiValueRef multi = ABRecordCopyValue(record, kABPersonInstantMessageProperty); for(CFIndex x=0;x<ABMultiValueGetCount(multi);x++) { CFDictionaryRef dict = ABMultiValueCopyValueAtIndex(multi, x); CFStringRef jabber = CFDictionaryGetValue(dict, kABPersonInstantMessageServiceJabber); if(CFDictionaryContainsKey(dict, kABPersonInstantMessageServiceJabber)) { NSLog(@"yes"); } else { NSLog(@"no"); } // only to make it possible to log to console NSString *jaab = (NSString *)jabber; NSLog(@"jabber adress: %@" , jaab); } CFRelease(dict); } } what I'm doing wrong?

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• Any implementations of graph st-ordering or ear-decomposition?

  - by chang

  I'm in the search for an implementation of an ear-decomposition algorithm (http://www.ics.uci.edu/~eppstein/junkyard/euler/ear.html). I examined networkx and didn't find one. Although the algorithm layout is vaguely in my mind, I'd like to see some reference implementation, too. I'm aware of Ulrik Brandes publication on a linear time Eager st-ordering algorithm, which results in an ear decomposition as a side product, if I understand correctly (it even includes pseudocode, which I'm trying to base my implementation on). Side problem: First step could be an st-ordering of a graph. Are there any implementations for st-ordering algorithms you know? Thanks for your input. I'd really like to contribute e.g. to networkx by implementing the ear-decomposition algorithm in python.

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• Create an object in C# from an F# object with optional arguments

  - by Mark Pearl

  I have a object in F# as follows... type Person(?name : string) = let name = defaultArg name "" member x.Name = name I want to be able to create an instance of this object in a C# project. I have added as a reference the correct libraries to the project and can see the object via intellisense however I am not sure on the correct syntaxt to create an instance of the object. Currently I have the following in my C# project - which the compiler doesn't like... var myObj1 = new Person("mark");

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• Automatic VM deployment

  - by Robert Wilson

  I have an idea to streamline deployments of prototypes within our team using VMs. The idea would be that a developer would be able to deploy their artifacts to Maven, then use a Web interface to pull them onto a development VM for integration/regression testing. They would then be able to to push those artifacts to a reference system, and finally onto production. I'm currently thinking of doing this myself using the vSphere Java API ( http://vijava.sourceforge.net/ ), and some simple scripting to grab artifacts from the Maven repository, configuration from SVN, and then start up a JBoss server. It feels like the kind of thing that may already be available though, has anyone heard of something similar?

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• SQL multiple primary keys - localization

  - by Max Malmgren

  I am trying to implement some localization in my database. It looks something like this (prefixes only for clarification) tbl-Categories ID Language Name tbl-Articles ID CategoryID Now, in my tbl-Categories, I want to have primary keys spanning ID and language, so that every combination of ID and language is unique. In tbl-Articles I would like a foreign key to reference ID in categories, but not Language, since I do not want to bind an article to a certain language, only category. Of course, I cannot add a foreign key to part of the primary key. I also cannot have the primary key only on the ID of categories, since then there can only be one language. Having no primary keys disables foreign keys altogether, and that is also not a great solution. Do you have any ideas how I can solve this in an elegant fashion? Thanks.

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• Who interrupts my thread?

  - by Thirler

  I understand what an InterruptedException does and why it is thrown. However in my application I get it when waiting for SwingUtilities.invokeAndWait() on a thread that is only known by my application, and my application never class Thread.interrupt() on any thread, also it never passes the reference of the thread on to anyone. So my question is: Who interrupts my thread? Is there any way to tell? Is there a reason why the InterruptedException doesn't contain the name of the Thread that requests the interrupt? I read that it could be a framework or library that does this, we use the following, but I can't think of reason for them to interrupt my thread: Hibernate Spring Log4J Mysql connector

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• Matching .NET References to Namespaces

  - by maxp

  This seems confusing to me - im creating a class library, and adding all the necessary references for the source files contained in it. Now, off the bat, there were over 300 compiler errors complaining about missing namespaces. The library will now compile after i just added all of the System.* references, however this is obviously not the best way. I.e. if a classes needs using System.Web.Script;, there is no System.Web.Script reference, how would i find out which one of these references contained it? System.Web didnt.

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• How to replace 'dash' with 'underscore' in an IIRF rule?

  - by jessegavin

  I have a web app which serves images based on the subdomain. We wanted to provide our users with a url like this: http://{username}.domain.com/images/myimage.jpg Instead of what we used to have: http://www.reallylongdomainname.com/users/{username}/images/myimage.jpg This makes the url shorter and less 'snoopable'. So I set up an IIRF .ini file to do some url rewriting and it works great except for the fact that some of our users folders have an underscore. And from what I've read, underscore is not a valid character in a domain name (even though IIS supports it). I want to know how I could do a find and replace in the $1 back reference so that a url like this: http://some-user.domain.com/... Could be rewritten to this: /users/some_user/.. Here's my IIRF rule. RewriteCond %{HTTP_HOST} ^(?!www)([^\.]+)\.domain\.com RewriteRule ^/(.*)$ /users/*1/$1 [L,I] Thanks for any help.

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• How to find the parent element using javascript

  - by Kalpana

  I want to change the background color of the table cell when radio button inside the cell is clicked. <table> <tr> <c:forEach items="#{books}" var="book"> <td align="center"> <h:selectOneRadio value="#{book.price}" onclick="this.parentElement.style.background-color='red';"> <f:selectItems value="#{books.getDetails()}" /> </h:selectOneRadio> </td> </c:forEach> </tr> </table> How to get the parent element reference.

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• Casting a primitive int to a Number

  - by Tamer

  Let's say that I have the following: int a = 2; Number b = (Number) a; System.out.println(b); // Prints 2 http://java.sun.com/docs/books/jls/first_edition/html/15.doc.html#238146 says that a primitive value may not be cast to a reference type. Does Java know to create an Integer from the primitive int and then cast to the superclass? How exactly does Java handle this behind the scenes? Thanks!

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• CouchDB Map/Reduce raises execption in reduce function?

  - by fuzzy lollipop

  my view generates keys in this format ["job_id:1234567890", 1271430291000] where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1 and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now function(keys,values,rereduce) { var now = new Date().valueOf(); var first = Number.MIN_VALUE; var last = Number.MAX_VALUE; if (rereduce) { first = Math.max(first,values[0].first); last = Math.min(last,values[0].last); } else { first = keys[0][0][1]; last = keys[keys.length-1][0][1]; } return {first:now - first, last:now - last}; } and when processing a query it constantly raises the following execption: function raised exception (new TypeError("keys has no properties", "", 1)) I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?

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• predicate subquery to return items by matching tags

  - by user3411663

  I have a many-to-many relationship between two entities; Item and Tag. I'm trying to create a predicate to take the selectedItem and return a ranking of items based on how many similar tags they have. So far I've tried: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(itemToTag, $item, $item in %@).@count > 0", selectedItem.itemToTag]; Any other iterations that have failed. It currently only returns the selectedItem in the list. I've found little on Subquery. Is there a guru out there that can help me refine this? Thanks in advance for the help!

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