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• What does ER_WARN_FIELD_RESOLVED mean?

  - by VolkerK

  When SHOW WARNINGS after a EXPLAIN EXTENDED shows a Note 1276 Field or reference 'test.foo.bar' of SELECT #2 was resolved in SELECT #1 what exactly does that mean and what impact does it have? In my case it prevents mysql from using what seems to be a perfectly good index. But it's not about fixing that specific query (as it is an irrelevant test). I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html butError: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED) Message: Field or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d isn't much of an explaination.

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• Nesting queries in SQL

  - by ZAX

  The goal of my query is to return the country name and its head of state if it's headofstate has a name starting with A, and the capital of the country has greater than 100,000 people utilizing a nested query. Here is my query: SELECT country.name as country, (SELECT country.headofstate from country where country.headofstate like 'A%') from country, city where city.population > 100000; I've tried reversing it, placing it in the where clause etc. I don't get nested queries. I'm just getting errors back, like subquery returns more than one row and such. If someone could help me out with how to order it, and explain why it needs to be a certain way, that'd be great.

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• Why first arg to execve() must be path to executable

  - by EBM

  I understand that execve() and family require the first argument of its argument array to be the same as the executable that is also pointed to by its first argument. That is, in this: execve(prog, args, env); args[0] will usually be the same as prog. But I can't seem to find information as to why this is. I also understand that executables (er, at least shell scripts) always have their calling path as the first argument when running, but I would think that the shell would do the work to put it there, and execve() would just call the executable using the path given in its first argument ("prog" from above), then passing the argument array ("args" from above) as one would on the command line.... i.e., I don't call scripts on the command line with a duplicate executable path in the args list.... /bin/ls /bin/ls /home/john Can someone explain?

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• ActionScript 2.0 problem with the object's _visible parameter

  - by GMan

  Hey guys, I've been trying to build something simple in Flash 8, and I stumbled across something weird I cannot explain: I have an object, and at some point of the program, I want it to be visible (it is invisible at first), so I write: _root.myObj._visible = true; _root.gameOver.swapDepths(_root.getNextHighestDepth()); //so it will be on the top and this works fine, the object becomes visible and etc. What I planned to happen next is that the user presses a button on that same object, and the object will go invisible: on(release) { trace(_root.myObj._visible); _root.myObj._visible = false; trace(_root.myObj._visible); _root.gotoAndPlay("three"); } The trace returns at first true and later on false, so the command works, but oddly the object stays visible, that's what I don't understand. Thanks everybody in advance.

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• programming question about numbers

  - by Syom

  it's a task, on which i think during whole day. i have four integer numbers a, b, c, d, and ineger x[1,40]. i must write a program, which can find the values of {a,b,c,d}, for which one of following equations is true for any (x<=40, x=1) x=a or x=b or x=a+b or x=a+b+c+d or x+a=c+d or x+a+b=c+d or ... x+a+b+c=d or ... it is very difficult to explain what i want to say. maybe the example will be helpful. example: if x=17, by {a=1,b=2,c=5,d=15} i can write x+a+b=c+d whole question is to present any x[1,40] by {a,b,c,d}. hope that you understand what i want to say, and thanks in advance

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• What type of websites does memcached speed up

  - by Saif Bechan

  I have read this article about 400% boost of your website. This is done by a combination of nginx and memcached. The how-to part of this website is quite good, but i mis the part where it says to what types of websites this applies. I know nginx is a http engine, I need no explanation for that. I thought memcached had something to do with caching database result. However i don't understand what this has to do with the http request, can someone please explain that to me. Another question I have is for what types of websites is this used. I have a website where the important part of the website consist of data that changes often. Often being minutes. Will this method still apply to me, or should I just stick with the basic boring setup of apache and nothing else.

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• Applet problem with IPlanet and Firefox (class not found)

  - by JB Hurteaux

  I have an applet which loads nicely when accessed locally (both IE and Firefox). However, when I put my webpage in a webserver (local IPlanet), it refuses to load on Firefox (but still fine on IE). I get the following error in the java console: load: class XXX.localprinting.LocalPrintingApplet.class not found. java.lang.ClassNotFoundException: XXX.localprinting.LocalPrintingApplet.class at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source) at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: java.io.IOException: open HTTP connection failed:https://XXX/test/XXX/localprinting/LocalPrintingApplet/class.class at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source) at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source) at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) ... 7 more Exception: java.lang.ClassNotFoundException: XXX.localprinting.LocalPrintingApplet.class Any idea what could explain the different behavior in the webserver? I researched the issue of "class not found" already but without finding something relevant.

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• Rails: unexpected behavior updating a shared instance

  - by Pascal Lindelauf

  I have a User object, that is related to a Post object via two different association paths: Post --(has_many)-- comments --(belongs to)-- writer (of type User) Post --(belongs to)-- writer (of type User) Say the following hold: user1.name == "Bill" post1.comments[1].writer == user1 post1.writer == user1 Now when I retrieve the post1 and its comments from the database and I update post1.comments[1].writer like so: post1.comments[1].writer.name = "John" I would expect post1.writer to equal "John" too. But it doesn't! It still equals "Bill". So there seems to be some caching going on, but the kind I would not expect. I would expect Rails to be clever enough to load exactly one instance of the user with name "Bill"; instead is appears to load two individual ones: one for each association path. Can someone explain how this works exactly and how I am to handle these types of situations the "Rails way"?

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• Should I include the binary in a Rails plugin or not?

  - by Nick Gorbikoff

  Hello. I'm trying to roll out a little Rails plugin that is basically is just a wrapper to a 7zip archiver. Should I include the 7zip binaries for windows, mac and linux with it or explain to user that it's a dependency and they need to get it working. I know it's not that difficult to install a 7zip, but what is the best practice in general. The reason I'm asking is cause I've ran so many times into gems that need some sort of dependency that doesn't compile properly or is not available in ready form for the OS in question and then I end up spending have a day hunting down for a binary or a way to compile the program. (Have happened to me both on Mac and Windows, not on Debian so far. )

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• Is it a good idea to work on header files only, just at the start of the project?

  - by m4design

  To explain my point further, I'm a beginner in programming, and I'm working on a small project. Instead of separating the .cpp file from the header file, I'm implementing the code in the header files, and making one .cpp file for testing. I do this to have less files, hence easier navigation. Then later I'll separate the code as it should be. Will this cause any problems? should I continue doing that? Thanks.

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• BufferedImage Help

  - by Eddy Freeman

  I posted a question in sun java forums sometime ago and i am finding it hard to understand the first response i received from the replier though it seems he gave me the correct approach to my problem. The link to the question is: http://forums.sun.com/thread.jspa?threadID=5436562&tstart=0 Someone replied that i should use BufferedImage and make tiles. I don't really understand what the tiles mean in connection with the BufferedImage. I would like someone to explain to me what the tiles are and how they are created in the BufferedImage. I have searched the web for a while but couldn't find any link that can help me understanding the basics of the tiles and creating the tiles. Any pointer to a site is also appreciated. I need help in understanding the tiles in connection with the BufferedImage and also how they are created.

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• nodejs response speed and nginx

  - by user1502440

  I'm just started testing nodejs, and wanted to get some help in understanding following behavior: Example #1: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.end('foo'); }).listen(1001, '0.0.0.0'); Example #2: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.write('foo'); res.end('bar'); }).listen(1001, '0.0.0.0'); When testing response time in Chrome: example #1 - 6-10ms example #2 - 200-220ms But, if test both examples through nginx proxy_pass server{ listen 1011; location / { proxy_pass http://127.0.0.1:1001; } } i get this: example #1 - 4-8ms example #2 - 4-8ms I am not an expert on either nodejs or nginx, and asking if someone can explain this? nodejs - v.0.8.1 nginx - v.1.2.2

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• Request attributes in jsf / icefaces behaves strange (survive request end)

  - by hubertg

  I have the following code in a listener method: FacesContext.getCurrentInstance().getExternalContext().getRequestMap().put("time", new Date()); When a button is clicked the following code is executed System.out.println(FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("time")); One could except that "time" is null when the listener was not executed while processing the current request, but: it seems like the "time" object survives the request processing. So when "time" has been set sometimes in the past it stays there... can anybody explain this? Thanks.

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• Why calling ISet<dynamic>.Contains() compiles, but throws an exception at runtime?

  - by Andrey Breslav

  Please, help me to explain the following behavior: dynamic d = 1; ISet<dynamic> s = new HashSet<dynamic>(); s.Contains(d); The code compiles with no errors/warnings, but at the last line I get the following exception: Unhandled Exception: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'System.Collections.Generic.ISet<object>' does not contain a definition for 'Contains' at CallSite.Target(Closure , CallSite , ISet`1 , Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1) at FormulaToSimulation.Program.Main(String[] args) in As far as I can tell, this is related to dynamic overload resolution, but the strange things are (1) If the type of s is HashSet<dynamic>, no exception occurs. (2) If I use a non-generic interface with a method accepting a dynamic argument, no exception occurs. Thus, it looks like this problem is related particularly with generic interfaces, but I could not find out what exactly causes the problem. Is it a bug in the compiler/typesystem, or legitimate behavior?

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• C# regex: negative lookahead fails with the single line option

  - by Sylverdrag

  I am trying to figure out why a regex with negative look ahead fails when the "single line" option is turned on. Example (simplified): <source>Test 1</source> <source>Test 2</source> <target>Result 2</target> <source>Test 3</source> This: <source>(?!.*<source>)(.*?)</source>(?!\s*<target) will fail if the single line option is on, and will work if the single line option is off. For instance, this works (disables the single line option): (?-s:<source>(?!.*<source>)(.*?)</source>(?!\s*<target)) My understanding is that the single line mode simply allows the dot "." to match new lines, and I don't see why it would affect the expression above. Can anyone explain what I am missing here?

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• generic function for extracting values from an array with one particular key in PHP

  - by Sabya

  Is it possible in PHP to extract values from an array with a particular key path and return an array of those values? I'll explain with an example: $user = array ( array( id => 1, email =>'[email protected]', project => array ('project_id' => 222, 'project_name' => 'design') ), array( id => 2, email =>'[email protected]', project => array ('project_id' => 333, 'project_name' => 'design') ) ); /** I have to write a function something like: */ $projectIds = extractValuesWithKey($user, array('project', 'project_id')); print_r($projectIds); Output: Array( [0] => 222, [1] => 333 )

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• usage of 2 charectors in single qoutes in c

  - by user1632141

  #include<stdio.h> int main() { char ch = 'A'; printf("%d\n",'ag'); printf("%d\n",'a'); printf("%d, %d, %d, %d", sizeof(ch), sizeof('a'), sizeof('Ag'), sizeof(3.14f)); return 0; } I used to have many doubts on the output of this question while running on g++ and gcc. But I have cleared almost all the doubts by referring these links: Single and double quotes in C/C++ Single quotes vs. double quotes in C I still need to understand one thing about the output of this question. Can someone please explain the output of printf("%d\n",'ag'); mentioned above in the program. How is it actually stored in the memory? The output for the program on the Linux/GCC platform is: 24935 97 1, 4, 4, 4

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• Why baseclass calls method of subclass?

  - by twlkyao

  I encounter some code like the following: BaseClass: public class BaseClass { String name = "Base"; public BaseClass() { printName(); } public void printName() { System.out.println(name + "——Base"); } } DrivedClass: public class SubClass extends BaseClass { String name = "Sub"; public SubClass() { printName(); } public void printName() { System.out.println(name + "——Sub"); } public static void main(String[] args) { new SubClass(); } } When run the code, the output is: null——Sub Sub——Sub while it should be: Base——Base Sub——Sub I wonder why the BaseClass constructor calls the SubClass method, can anybody explain this? Thanks in advance.

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• fread() behaves weird

  - by Cres

  hi, I have a problem in a C program of mine where after I use fread(), the file pointer goes to the end of the file sometimes. I'll try to explain better - the code looks something like: dummy = ftell(fp); fread(&buf, sizeof(unsigned char), 8, fp); dummy = ftell(fp); where fp is a file pointer to an opened file (opened it with "w+", I'm using it as a binary file and I know i'm supposed to have a "b" in there too, but I heard its not really important to add it..), dummy is just an unsigned long variable, and buf is unsigned char[8] now, when debugging, at the ftell before the fread, dummy is 262062 at the ftell after the fread, dummy is 262640 even though I only 'moved' 8 bytes.. does anyone have any idea what can be the cause of this..? thanks for your help :)

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• The pros and cons of use JSON for WCF service

  - by brz dot net

  What are the pros and cons of the following 2 cases: Case I: Traditional way: Add service reference in project. Create object and Get data from service on server side and bind to asp.net grid. Case II: Update Service for JSON behavior. Add service reference in project. Call service from javascript to get data. Bind data to jquery grid. Which one is the best approach and why?(Not developer point of view) If there is another approach which is more optimized, please explain it.

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• Why are difference lists more efficient than regular concatenation?

  - by Craig Innes

  I am currently working my way through the Learn you a haskell book online, and have come to a chapter where the author is explaining that some list concatenations can be ineffiecient: For example ((((a ++ b) ++ c) ++ d) ++ e) ++ f Is supposedly inefficient. The solution the author comes up with is to use 'difference lists' defined as newtype DiffList a = DiffList {getDiffList :: [a] -> [a] } instance Monoid (DiffList a) where mempty = DiffList (\xs -> [] ++ xs) (DiffList f) `mappend` (DiffList g) = DiffList (\xs -> f (g xs)) I am struggling to understand why DiffList is more computationally efficient than a simple concatenation in some cases. Could someone explain to me in simple terms why the above example is so inefficient, and in what way the DiffList solves this problem?

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• passing values to pages

  - by Indranil Mutsuddy

  Hello friends, What i am trying here is to pass values to other pages. When i include the following code private void Button1_Click(object sender, System.EventArgs e) { // Value sent using HttpResponse Response.Redirect("WebForm5.aspx?Name="+txtName.Text); } if (Request.QueryString["Name"]!= null) Response.write( Request.QueryString["Name"]); everything works fine the name gets displayed. Now if use MemberId instead, though i can see the Id in the Url, but while checking for Null in other page, its true. Whats wrong?? Now I tried the same thing using session i.e. Session["MemberId"] = this.TxtEnterMemberId.Text; if (MemberSex.Equals("M")) Response.Redirect("PatientDetailsMale.aspx",false ); Page_load event of the other page if (Session["MemberId"] != null) mid = Session["MemberId"].ToString(); IT Works..Could u guys explain the behaviour please? P.S. Can anyone give a breif in layman words about SessionId and its usage. Thanking you, Indranil

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• How extension methods work in background ?

  - by Freshblood

  I am just cuirous about behind of extension method mechanism.Some questions and answer appear in my mind. MyClass.OrderBy(x=>x.a).OrderBy(x=>x.b); I was guessing that mechanism was first orderby method works and order them by a member then returns sorted items in IEnumarable interface then next Orderby method of IEnumarable Order them for b paramater.But i am wrong when i look at this linq query. MyClass.Orderby(x=>x.a).ThenOrderBy(x=>x.b); this is slightly different and tells me that i am wrong.Because this is not ordering by a then b and not possible to have such result if i was right.This get me confuse enough... Similiar structure is possible to write withot extension methods as first query but second is not possible.This prove i am wrong . Can u explain it ?

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• Scriptom (groovy) leaves Excel process running - am I doing something wrong?

  - by Alex Stoddard

  I am using the Scriptom extension to Groovy 1.7.0 to automate some processing using Excel 2007 under Windows XP. This always seems to leave an Excel process running despite my calling quit on the excel activeX object. (There is a passing reference to this phenomenon in the Scriptom example documentation too.) Code looks like: import org.codehaus.groovy.scriptom.ActiveXObject; def xls = new ActiveXObject("Excel.Application") xls.Visible = true // do xls stuff xls.Quit() The visible excel window does disappear but an EXCEL process is left in the task manager (and more processes pile up with each run of the script). There are no error message or exceptions. Can anyone explain why the Excel process is left behind and is there any way to prevent it from happening?

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• PropelBundle database:create for postgres

  - by Karol85

  I've installed propel bundle for symfony2. my database configuration is: propel: dbal: driver: pgsql user: postgres password: postgres dsn: pgsql:host=localhost;port=5432;dbname=test_database options: {} attributes: {} When i wan to create this database from console (console propel: database:create) i have got strange error : Unable to open PDO connection [wrapped: SQLSTATE[08006] [7] FATAL: database "pgsql" does not exist. i created pgsql database on my localhost and everything was good. Database "test_database" was succesfull created. Can somebody explain me why i got this previous error? On mysql i've created database without any problems.

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